Accelerated Aging Disease
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Progeroid syndromes (PS) are a group of rare
genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...
s that mimic
physiological Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
aging Ageing ( BE) or aging ( AE) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In ...
, making affected individuals appear to be older than they are. The term ''progeroid syndrome'' does not necessarily imply
progeria Progeria is a specific type of progeroid syndrome, also known as Hutchinson–Gilford syndrome. A single gene mutation is responsible for progeria. The gene, known as lamin A (LMNA), makes a protein necessary for holding the Nucleus of the cell ...
(
Hutchinson–Gilford progeria syndrome Progeria is a specific type of progeroid syndrome, also known as Hutchinson–Gilford syndrome. A single gene mutation is responsible for progeria. The gene, known as lamin A (LMNA), makes a protein necessary for holding the Nucleus of the cell ...
), which is a specific type of progeroid syndrome. ''Progeroid'' means "resembling premature aging," a definition that can apply to a broad range of diseases. Familial
Alzheimer's disease Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...
and familial
Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms becom ...
are two well-known accelerated-aging diseases that are more frequent in older individuals. They affect only one tissue and can be classified as unimodal progeroid syndromes. Segmental progeria, which is more frequently associated with the term ''progeroid syndrome,'' tends to affect multiple or all tissues while causing affected individuals to exhibit only some of the features associated with aging. All disorders within this group are thought to be monogenic, meaning they arise from
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mi ...
s of a single
gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
. Most known PS are due to genetic mutations that lead to either defects in the
DNA repair DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA dam ...
mechanism or defects in lamin A/C. Examples of PS include
Werner syndrome Werner syndrome (WS) or Werner's syndrome, also known as "adult progeria",James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). Saunders. . is a rare, autosomal recessive disorder ...
(WS),
Bloom syndrome Bloom syndrome (often abbreviated as BS in literature) is a rare autosomal recessive genetic disorder characterized by short stature, predisposition to the development of cancer, and genomic instability. BS is caused by mutations in the ''BLM'' gen ...
(BS),
Rothmund–Thomson syndrome Rothmund–Thomson syndrome (RTS) is a rare autosomal recessive skin condition. There have been several reported cases associated with osteosarcoma. A hereditary basis, mutations in the DNA helicase ''RECQL4'' gene, causing problems during initi ...
(RTS),
Cockayne syndrome Cockayne syndrome (CS), also called Neill-Dingwall syndrome, is a rare and fatal autosomal recessive neurodegenerative disorder characterized by growth failure, impaired development of the nervous system, abnormal sensitivity to sunlight (photosen ...
(CS),
xeroderma pigmentosum Xeroderma pigmentosum (XP) is a genetic disorder in which there is a decreased ability to repair DNA damage such as that caused by ultraviolet (UV) light. Symptoms may include a severe sunburn after only a few minutes in the sun, freckling in sun- ...
(XP),
trichothiodystrophy Trichothiodystrophy (TTD) is an autosomal recessive inherited disorder characterised by brittle hair and intellectual impairment. The word breaks down into ''tricho'' – "hair", '' thio'' – "sulphur", and ''dystrophy'' – "wasting away" or lit ...
(TTD), combined
xeroderma pigmentosum Xeroderma pigmentosum (XP) is a genetic disorder in which there is a decreased ability to repair DNA damage such as that caused by ultraviolet (UV) light. Symptoms may include a severe sunburn after only a few minutes in the sun, freckling in sun- ...
-
Cockayne syndrome Cockayne syndrome (CS), also called Neill-Dingwall syndrome, is a rare and fatal autosomal recessive neurodegenerative disorder characterized by growth failure, impaired development of the nervous system, abnormal sensitivity to sunlight (photosen ...
(XP-CS),
restrictive dermopathy Restrictive dermopathy (RD) is a rare, lethal autosomal recessive skin condition characterized by syndromic facies, tight skin, sparse or absent eyelashes, and secondary joint changes.James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews ...
(RD), and
Hutchinson–Gilford progeria syndrome Progeria is a specific type of progeroid syndrome, also known as Hutchinson–Gilford syndrome. A single gene mutation is responsible for progeria. The gene, known as lamin A (LMNA), makes a protein necessary for holding the Nucleus of the cell ...
(HGPS). Individuals with these disorders tend to have a reduced lifespan. Progeroid syndromes have been widely studied in the fields of aging,
regeneration Regeneration may refer to: Science and technology * Regeneration (biology), the ability to recreate lost or damaged cells, tissues, organs and limbs * Regeneration (ecology), the ability of ecosystems to regenerate biomass, using photosynthesis ...
,
stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type o ...
s, and
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
. The most widely studied of the progeroid syndromes are Werner syndrome and Hutchinson–Gilford progeria, as they are seen to most resemble natural aging.


Defects in DNA repair

One of the main causes of progeroid syndromes is
genetic mutations In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mit ...
, which lead to defects in the cellular processes which repair DNA. The
DNA damage theory of aging The DNA damage theory of aging proposes that aging is a consequence of unrepaired accumulation of naturally occurring DNA damage. Damage in this context is a DNA alteration that has an abnormal structure. Although both mitochondrial and nuclear ...
proposes that aging is a consequence of the accumulation of naturally occurring DNA damages. The accumulated damage may arise from
reactive oxygen species In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen () p ...
(ROS), chemical reactions (e.g. with
intercalating agent In biochemistry, intercalation is the insertion of molecules between the planar bases of deoxyribonucleic acid (DNA). This process is used as a method for analyzing DNA and it is also the basis of certain kinds of poisoning. There are several ...
s),
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
,
depurination Depurination is a chemical reaction of purine deoxyribonucleosides, deoxyadenosine and deoxyguanosine, and ribonucleosides, adenosine or guanosine, in which the β-N-glycosidic bond is hydrolytically cleaved releasing a nucleic base, adenine or gua ...
, and
deamination Deamination is the removal of an amino group from a molecule. Enzymes that catalyse this reaction are called deaminases. In the human body, deamination takes place primarily in the liver, however it can also occur in the kidney. In situations of e ...
. Mutations in three classes of DNA repair proteins, RecQ protein-like helicases (RECQLs),
nucleotide excision repair Nucleotide excision repair is a DNA repair mechanism. DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens. Three excision repair pathways exist to repair single stranded DNA damage: Nucle ...
(NER) proteins, and nuclear envelope proteins
LMNA Pre-lamin A/C or lamin A/C is a protein that in humans is encoded by the ''LMNA'' gene. Lamin A/C belongs to the lamin family of proteins. Function In the setting of ZMPSTE24 deficiency, the final step of lamin processing does not occur, res ...
(lamins) have been associated with the following progeroid syndromes: * Werner syndrome (WS) * Bloom syndrome (BS) * Rothmund–Thomson syndrome (RTS) * Cockayne syndrome (CS) * Xeroderma pigmentosum (XP) * Trichothiodystrophy (TTD)


RecQ-associated PS

''RecQ'''' i''s a family of conserved ATP-dependent
helicase Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separatin ...
s required for repairing DNA and preventing deleterious recombination and
genomic instability Genome instability (also genetic instability or genomic instability) refers to a high frequency of mutations within the genome of a cellular lineage. These mutations can include changes in nucleic acid sequences, chromosomal rearrangements or aneu ...
. ''DNA helicases'' are enzymes that bind to double-stranded DNA and temporarily separate them. This unwinding is required in replication of the genome during
mitosis In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
, but in the context of PS, it is a required step in repairing damaged DNA. Thus, DNA helicases, such as RecQ, maintain the integrity of a cell, and defects in these helicases are linked to an increased predisposition to
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
and aging
phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
s. Thus, individuals with RecQ-associated PS show an increased risk of developing cancer, which is caused by genomic instability and increased rates of mutation. There are five genes encoding RecQ in humans (RECQ1-5), and defects in RECQL2/WRN, RECQL3/BLM and RECQL4 lead to Werner syndrome (WS), Bloom syndrome (BS), and Rothmund–Thomson syndrome (RTS), respectively. On the cellular level, cells of affected individuals exhibit chromosomal abnormalities, genomic instability, and sensitivity to
mutagen In genetics, a mutagen is a physical or chemical agent that permanently changes nucleic acid, genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can ca ...
s.


Werner syndrome

''Werner syndrome'' (WS) is a rare
autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
disorder. It has a global incidence rate of less than 1 in 100,000 live births, although incidences in Japan and Sardinia are higher, where it affects 1 in 20,000-40,000 and 1 in 50,000, respectively. As of 2006, there were approximately 1,300 reported cases of WS worldwide. Affected individuals typically grow and develop normally until
puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a boy. ...
, when they do not experience the typical adolescent growth spurt. The mean age of diagnosis is twenty-four. The median and mean age of death are 47-48 and 54 years, respectively;Oshima J, Martin GM, Hisama FM. Werner Syndrome. 2002 Dec 2 pdated 2012 Dec 13 In: Pagon RA, Bird TD, Dolan CR, et al., editors. GeneReviews™ nternet Seattle (WA): University of Washington, Seattle; 1993-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1514/ the main cause of death is
cardiovascular disease Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...
or cancer. Affected individuals can exhibit growth retardation, short stature, premature graying of hair,
hair loss Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarri ...
, wrinkling, prematurely aged faces, beaked noses, skin
atrophy Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations (which can destroy the gene to build up the organ), poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply t ...
(wasting away) with
scleroderma Scleroderma is a group of autoimmune diseases that may result in changes to the skin, blood vessels, muscles, and internal organs. The disease can be either localized to the skin or involve other organs, as well. Symptoms may include areas of ...
-like
lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...
s, loss of fat tissues, abnormal fat deposition leading to thin legs and arms, and severe
ulcer An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing o ...
ations around the
Achilles tendon The Achilles tendon or heel cord, also known as the calcaneal tendon, is a tendon at the back of the lower leg, and is the thickest in the human body. It serves to attach the plantaris, gastrocnemius (calf) and soleus muscles to the calcaneus (h ...
and
malleoli A malleolus is the bony prominence on each side of the human ankle. Each leg is supported by two bones, the tibia on the inner side (medial) of the leg and the fibula on the outer side (lateral) of the leg. The medial malleolus is the promine ...
. Other signs include change in voice, making it weak, hoarse, or high-pitched; atrophy of
gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...
s, leading to reduced
fertility Fertility is the capability to produce offspring through reproduction following the onset of sexual maturity. The fertility rate is the average number of children born by a female during her lifetime and is quantified demographically. Fertili ...
; bilateral
cataract A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
s (clouding of lens); premature
arteriosclerosis Arteriosclerosis is the thickening, hardening, and loss of elasticity of the walls of Artery, arteries. This process gradually restricts the blood flow to one's organs and tissues and can lead to severe health risks brought on by atherosclerosis ...
(thickening and loss of elasticity of arteries);
calcinosis Calcinosis is the formation of calcium deposits in any soft tissue. It is a rare condition that has many different causes. These range from infection and injury to systemic diseases like kidney failure. Types Dystrophic calcification The most c ...
(calcium deposits in blood vessels);
atherosclerosis Atherosclerosis is a pattern of the disease arteriosclerosis in which the wall of the artery develops abnormalities, called lesions. These lesions may lead to narrowing due to the buildup of atheroma, atheromatous plaque. At onset there are usu ...
(blockage of blood vessels);
type 2 diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, ...
; loss of bone mass;
telangiectasia Telangiectasias, also known as spider veins, are small dilated blood vessels that can occur near the surface of the skin or mucous membranes, measuring between 0.5 and 1 millimeter in diameter. These dilated blood vessels can develop anywhere on ...
; and
malignancies Malignancy () is the tendency of a medical condition to become progressively worse. Malignancy is most familiar as a characterization of cancer. A ''malignant'' tumor contrasts with a non-cancerous ''benign'' tumor in that a malignancy is not s ...
. In fact, the prevalence of rare cancers, such as
meningioma Meningioma, also known as meningeal tumor, is typically a slow-growing tumor that forms from the meninges, the membranous layers surrounding the brain and spinal cord. Symptoms depend on the location and occur as a result of the tumor pressing o ...
s, are increased in individuals with Werner syndrome. Approximately 90% of individuals with Werner Syndrome have any of a range of mutations in the eponymous gene, WRN, the only gene currently connected to Werner syndrome. WRN encodes the WRNp protein, a 1432 amino acid protein with a central domain resembling members of the RecQ helicases. WRNp is active in unwinding DNA, a step necessary in DNA repair and
DNA replication In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritanc ...
. Since WRNp's function depends on DNA, it is only functional when localized to the nucleus. Mutations that cause Werner syndrome only occur at the regions of the gene that encode for protein and not at
non-coding Non-coding DNA (ncDNA) sequences are components of an organism's DNA that do not encode protein sequences. Some non-coding DNA is transcribed into functional non-coding RNA molecules (e.g. transfer RNA, microRNA, piRNA, ribosomal RNA, and regula ...
regions. These mutations can have a range of effects. They may decrease the stability of the transcribed
messenger RNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during the p ...
(mRNA), which increases the rate at which they are degraded. With fewer mRNA, fewer are available to be
translated Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...
into the WRNp protein. Mutations may also lead to the truncation (shortening) of the WRNp protein, leading to the loss of its nuclear localization signal sequence, which would normally transport it to the nucleus where it can interact with the DNA. This leads to a reduction in DNA repair. Furthermore, mutated proteins are more likely to be degraded than normal WRNp. Apart from causing defects in DNA repair, its aberrant association with
p53 p53, also known as Tumor protein P53, cellular tumor antigen p53 (UniProt name), or transformation-related protein 53 (TRP53) is a regulatory protein that is often mutated in human cancers. The p53 proteins (originally thought to be, and often s ...
down-regulates the function of p53, leading to a reduction in p53-dependent
apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...
and increase the survival of these dysfunctional cells. Cells of affected individuals have reduced lifespan in
culture Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups.Tyl ...
, more chromosome breaks and
translocations In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal-, and Robertsonian translocation. Reciprocal translo ...
and extensive deletions. These DNA damages, chromosome aberrations and mutations may in turn cause more RecQ-independent aging phenotypes.


Bloom syndrome

''Bloom syndrome'' (BS) is a very rare autosomal recessive disorder. Incidence rates are unknown, although it is known to be higher in people of
Ashkenazi Jew Ashkenazi Jews ( ; he, יְהוּדֵי אַשְׁכְּנַז, translit=Yehudei Ashkenaz, ; yi, אַשכּנזישע ייִדן, Ashkenazishe Yidn), also known as Ashkenazic Jews or ''Ashkenazim'',, Ashkenazi Hebrew pronunciation: , singu ...
ish background, presenting in around 1 in 50,000. Approximately one-third of individuals who have BS are of Ashkenazi Jewish descent. There is no evidence from the Bloom's Syndrome Registry or from the peer-reviewed medical literature that BS is a progeroid condition associated with advanced aging. It is, however, associated with early-onset cancer and adult-type diabetes and also with Werner syndrome, which is a progeroid syndrome, through mutation in the RecQ helicases. These associations have led to the speculation that BS could be associated with aging. Unfortunately, the average lifespan of persons with Bloom syndrome is 27 years; consequently, there is insufficient information to completely rule out the possibility that BS is associated with some features of aging. People with BS start their life with a low weight and length when they are born. Even as adults, they typically remain under 5 feet tall. Individuals with BS are characterized by low weight and height and abnormal facial features, particularly a long, narrow face with a small lower jaw, a large nose and prominent ears. Most also develop
photosensitivity Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light. In medicine, the term is principally used for abnormal reactions of the skin, and two types are distinguished, photoallergy and phototoxicity. ...
, which causes the blood vessels to be dilated and leads to reddening of the skin, usually presented as a "butterfly-shaped patch of reddened skin across the nose and cheeks". Other characteristics of BS include
learning disabilities Learning disability, learning disorder, or learning difficulty (British English) is a condition in the brain that causes difficulties comprehending or processing information and can be caused by several different factors. Given the "difficult ...
, an increased risk of
diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
,
gastroesophageal reflux Gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD) is one of the upper gastrointestinal chronic diseases where stomach content persistently and regularly flows up into the esophagus, resulting in symptoms and/ ...
(GER), and
chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce ...
(COPD). GER may also lead to recurrent infections of the upper respiratory tract,
ears An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists o ...
, and lungs during infancy. BS causes
infertility Infertility is the inability of a person, animal or plant to reproduce by natural means. It is usually not the natural state of a healthy adult, except notably among certain eusocial species (mostly haplodiploid insects). It is the normal state ...
in males and reduced fertility and early-onset
menopause Menopause, also known as the climacteric, is the time in women's lives when menstrual periods stop permanently, and they are no longer able to bear children. Menopause usually occurs between the age of 47 and 54. Medical professionals often d ...
in females. In line with any RecQ-associated PS, people with BS have an increased risk of developing cancer, often more than one type. BS is caused by mutations in the BLM gene, which encodes for the
Bloom syndrome protein Bloom syndrome protein is a protein that in humans is encoded by the ''BLM'' gene and is not expressed in Bloom syndrome. The Bloom syndrome gene product is related to the RecQ subset of DExH box-containing DNA helicases and has both DNA-stimula ...
, a RecQ helicase. These mutations may be
frameshift Ribosomal frameshifting, also known as translational frameshifting or translational recoding, is a biological phenomenon that occurs during translation that results in the production of multiple, unique proteins from a single mRNA. The process can ...
,
missense In genetics, a missense mutation is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. It is a type of nonsynonymous substitution. Substitution of protein from DNA mutations Missense mu ...
, non-sense, or mutations of other kinds and are likely to cause deletions in the gene product. Apart from helicase activity that is common to all RecQ helices, it also acts to prevent inappropriate
homologous recombination Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
. During replication of the genome, the two copies of DNA, called
sister chromatids A sister chromatid refers to the identical copies (chromatids) formed by the DNA replication of a chromosome, with both copies joined together by a common centromere. In other words, a sister chromatid may also be said to be 'one-half' of the dup ...
, are held together through a structure called the
centromere The centromere links a pair of sister chromatids together during cell division. This constricted region of chromosome connects the sister chromatids, creating a short arm (p) and a long arm (q) on the chromatids. During mitosis, spindle fibers a ...
. During this time, the homologous (corresponding) copies are in close physical proximity to each other, allowing them to 'cross' and exchange genetic information, a process called
homologous recombination Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
. Defective homologous recombination can cause mutation and genetic instability. Such defective recombination can introduce gaps and breaks within the genome and disrupt the function of genes, possibly causing growth retardation, aging and elevated risk of cancer. It introduces gaps and breaks within the genome and disrupts the function of genes, often causing retardation of growth, aging and elevated risks of cancers. The Bloom syndrome protein interacts with other proteins, such as topoisomerase IIIα and RMI2, and suppresses illegitimate recombination events between sequences that are divergent from strict homology, thus maintaining genome stability. Individuals with BS have a
loss-of-function mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitos ...
, which means that the illegitimate recombination is no longer suppressed, leading to higher rates of mutation (~10-100 times above normal, depending on cell type).


NER protein-associated PS

''Nucleotide excision repair'' is a DNA repair mechanism. There are three excision repair pathways: nucleotide excision repair (NER),
base excision repair Base excision repair (BER) is a cellular mechanism, studied in the fields of biochemistry and genetics, that repairs damaged DNA throughout the cell cycle. It is responsible primarily for removing small, non-helix-distorting base lesions from t ...
(BER), and
DNA mismatch repair DNA mismatch repair (MMR) is a system for recognizing and repairing erroneous insertion, deletion, and mis-incorporation of nucleobase, bases that can arise during DNA replication and Genetic recombination, recombination, as well as DNA repair, r ...
(MMR). In NER, the damaged DNA strand is removed and the undamaged strand is kept as a template for the formation of a complementary sequence with DNA polymerase.
DNA ligase DNA ligase is a specific type of enzyme, a ligase, () that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond. It plays a role in repairing single-strand breaks in duplex DNA in living organ ...
joins the strands together to form dsDNA. There are two subpathways for NER, which differ only in their mechanism for recognition: global genomic NER (GG-NER) and transcription coupled NER (TC-NER). Defects in the NER pathway have been linked to progeroid syndromes. There are 28 genes in this pathway. Individuals with defects in these genes often have developmental defects and exhibit
neurodegeneration A neurodegenerative disease is caused by the progressive loss of structure or function of neurons, in the process known as neurodegeneration. Such neuronal damage may ultimately involve cell death. Neurodegenerative diseases include amyotrophic ...
. They can also develop CS, XP, and TTD, often in combination with each other, as with combined xeroderma pigmentosa-Cockayne syndrome (XP-CS). Variants of these diseases, such as DeSanctis–Cacchione syndrome and Cerebro-oculo-facio-skeletal (COFS) syndrome, can also be caused by defects in the NER pathway. However, unlike RecQ-associated PS, not all individuals affected by these diseases have increased risk of cancer. All these disorders can be caused by mutations in a single gene, XPD, or in other genes.


Cockayne syndrome

''Cockayne syndrome'' (CS) is a rare autosomal recessive PS. There are three types of CS, distinguished by severity and age of onset. It occurs at a rate of about 1 in 300,000-500,000 in the United States and Europe. The mean age of death is ~12 years, although the different forms differ significantly. Individuals with the type I (or classical) form of the disorder usually first show symptoms between one and three years and have lifespans of between 20 and 40 years. Type II Cockayne syndrome (CSB) is more severe: symptoms present at birth and individuals live to approximately 6–7 years of age. Type III has the mildest symptoms, first presents later in childhood, and the cause of death is often severe nervous system deterioration and respiratory tract infections. Individuals with CS appear prematurely aged and exhibit severe growth retardation leading to short stature. They have a
small head Microcephaly (from New Latin ''microcephalia'', from Ancient Greek μικρός ''mikrós'' "small" and κεφαλή ''kephalé'' "head") is a medical condition involving a smaller-than-normal head. Microcephaly may be present at birth or it ...
(less than the -3 standard deviation), fail to gain weight and
failure to thrive Failure to thrive (FTT), also known as weight faltering or faltering growth, indicates insufficient weight gain or absence of appropriate physical growth in children. FTT is usually defined in terms of weight, and can be evaluated either by a low ...
. They also have extreme
cutaneous Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different de ...
photosensitivity (sensitivity to sunlight), neurodevelopmental abnormalities, and deafness, and often exhibit lipoatrophy, atrophic skin, severe
tooth decay Tooth decay, also known as cavities or caries, is the breakdown of teeth due to acids produced by bacteria. The cavities may be a number of different colors from yellow to black. Symptoms may include pain and difficulty with eating. Complicatio ...
, sparse hair, calcium deposits in neurons, cataracts, sensorineural hearing loss,
pigmentary retinopathy Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision (side and upper or lower visual field). As peripheral vision worsens, people may ...
, and bone abnormalities. However, they do not have a higher risk of cancer. Type I and II are known to be caused by mutation of a specific gene. CSA is caused by mutations in the '' cross-complementing gene 8'' (''ERCC8''), which encodes for the CSA protein. These mutations are thought to cause alternate splicing of the pre-mRNA which leads to an abnormal protein. CSB is caused by mutations in the ''
ERCC6 DNA excision repair protein ERCC-6 (also CS-B protein) is a protein that in humans is encoded by the ''ERCC6'' gene. The ''ERCC6'' gene is located on the long arm of chromosome 10 at position 11.23.NIH. "ERCC6 Gene." Genetics Home Reference. Natio ...
'' gene, which encodes the CSB protein. CSA and CSB are involved in transcription-coupled NER (TC-NER), which is involved in repairing DNA; they
ubiquitin Ubiquitin is a small (8.6 kDa) regulatory protein found in most tissues of eukaryotic organisms, i.e., it is found ''ubiquitously''. It was discovered in 1975 by Gideon Goldstein and further characterized throughout the late 1970s and 1980s. Fo ...
ate
RNA polymerase II RNA polymerase II (RNAP II and Pol II) is a multiprotein complex that transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNAP enzymes found in the nucleus of eukaryoti ...
, halting its progress thus allowing the TC-NER mechanism to be carried out. The ubiquitinated RNAP II then dissociates and is degraded via the
proteasome Proteasomes are protein complexes which degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds. Enzymes that help such reactions are called proteases. Proteasomes are part of a major mechanism by w ...
. Mutations in ERCC8, ERCC6, or both mean DNA is no longer repaired through TC-NER, and the accumulation of mutations leads to cell death, which may contribute to the symptoms of Cockayne syndrome.


Xeroderma pigmentosum

''Xeroderma pigmentosum'' (XP) is a rare autosomal recessive disorder, affecting about one per million in the United States and autochthonic Europe populations but with a higher incidence rate in Japan, North Africa, and the Middle East. There have been 830 published cases from 1874 to 1982. The disorder presents at infancy or early childhood. Xeroderma pigmentosum mostly affects the eye and skin. Individuals with XP have extreme sensitivity to light in the
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...
range starting from one to two years of age, and causes
sunburn Sunburn is a form of radiation burn that affects living tissue, such as skin, that results from an overexposure to ultraviolet (UV) radiation, usually from the Sun. Common symptoms in humans and animals include: red or reddish skin that is ho ...
,
freckling Freckles are clusters of concentrated melaninized cells which are most easily visible on people with a fair complexion. Freckles do not have an increased number of the melanin-producing cells, or melanocytes, but instead have melanocytes that ...
of skin, dry skin and pigmentation after exposure. When the eye is exposed to sunlight, it becomes irritated and bloodshot, and the
cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...
becomes cloudy. Around 30% of affected individuals also develop neurological abnormalities, including
deafness Deafness has varying definitions in cultural and medical contexts. In medical contexts, the meaning of deafness is hearing loss that precludes a person from understanding spoken language, an audiological condition. In this context it is written ...
, poor coordination, decreased intellectual abilities, difficulty swallowing and talking, and seizures; these effects tend to become progressively worse over time. All affected individuals have a 1000-fold higher risk of developing
skin cancer Skin cancers are cancers that arise from the skin. They are due to the development of abnormal cells that have the ability to invade or spread to other parts of the body. There are three main types of skin cancers: basal-cell skin cancer (BCC) ...
: half of the affected population develop skin cancer by age 10, usually at areas most exposed to sunlight (e.g. face, head, or neck). The risk for other cancers such as
brain tumor A brain tumor occurs when abnormal cells form within the brain. There are two main types of tumors: malignant tumors and benign (non-cancerous) tumors. These can be further classified as primary tumors, which start within the brain, and seconda ...
s,
lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissue (biology), tissues of the lung. Lung carcinomas derive from tran ...
and
eye cancer Eye neoplasms can affect all parts of the eye, and can be a benign tumor or a malignant tumor (cancer). Eye cancers can be primary (starts within the eye) or metastatic cancer (spread to the eye from another organ). The two most common cancers th ...
s also increase. There are eight types of XP (XP-A through XP-G), plus a variant type (XP-V), all categorized based on the genetic cause. XP can be caused by mutations in any of these genes: ''
DDB2 DNA damage-binding protein 2 is a protein that in humans is encoded by the ''DDB2'' gene. Structure As indicated by Rapić-Otrin et al. in 2003, the ''DDB2'' gene is located on human chromosome 11p11.2, spans a region of approximately 24 – 26 ...
'', ''
ERCC2 __NOTOC__ ERCC2, or XPD is a protein involved in transcription-coupled nucleotide excision repair. The XPD (ERCC2) gene encodes for a 2.3-kb mRNA containing 22 exons and 21 introns. The XPD protein contains 760 amino acids and is a polypeptide ...
'', ''
ERCC3 XPB (xeroderma pigmentosum type B) is an ATP-dependent DNA helicase in humans that is a part of the TFIIH transcription factor complex. Structure The 3D-structure of the archaeal homolog of XPB has been solved by X-ray crystallography by Dr. Jo ...
'', ''
ERCC4 ERCC4 is a protein designated as DNA repair endonuclease XPF that in humans is encoded by the ''ERCC4'' gene. Together with ERCC1, ERCC4 forms the ERCC1-XPF enzyme complex that participates in DNA repair and DNA recombination. The nuclease enzy ...
'', '' ERCC5'', ''
XPA DNA repair protein complementing XP-A cells is a protein that in humans is encoded by the ''XPA'' gene. Function Nucleotide excision repair (NER) is a major pathway for repairing a variety of bulky DNA damages including those introduced by UV i ...
'', '' XPC''. These genes are all involved in the NER repair pathway that repairs damaged DNA. The variant form, XP-V, is caused by mutations in the ''
POLH DNA polymerase eta (Pol η), is a protein that in humans is encoded by the ''POLH'' gene. DNA polymerase eta is a eukaryotic DNA polymerase involved in the DNA repair by translesion synthesis. The gene encoding DNA polymerase eta is POLH, also k ...
'' gene, which unlike the rest does not code for components of the NER pathway but produces a DNA polymerase that allows accurate
translesion synthesis DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA dama ...
of DNA damage resulting from UV radiation; its mutation leads to an overall increase in UV-dependent mutation, which ultimately causes the symptoms of XP.


Trichothiodystrophy

''Trichothiodystrophy'' (TTD) is a rare autosomal recessive disease whose symptoms span across multiple systems and can vary greatly in severity. The incidence rate of TTD is estimated to be 1.2 per million in Western Europe. Milder cases cause sparse and brittle hair, which is due to the lack of
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
, an element that is part of the matrix proteins that give hair its strength. More severe cases cause delayed development, significant intellectual disability, and recurrent infection; the most severe cases see death at infancy or early childhood. TTD also affects the mother of the affected child during pregnancy, when she may experience pregnancy-induced high blood pressure and develop
HELLP syndrome HELLP syndrome is a complication of pregnancy; the acronym stands for hemolysis, elevated liver enzymes, and low platelet count. It usually begins during the last three months of pregnancy or shortly after childbirth. Symptoms may include feelin ...
. The baby has a high risk of being born prematurely and will have a low
birth weight Birth weight is the body weight of a baby at its birth. The average birth weight in babies of European descent is , with the normative range between . On average, babies of South Asian and Chinese descent weigh about . As far as low birth weight ...
. After birth, the child's normal growth is retarded, resulting in a short stature. Other symptoms include scaly skin, abnormalities of the fingernails and toenails, clouding of the lens of the eye from birth (
congenital A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...
cataracts A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...
), poor co-ordination, and
ocular Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and con ...
and skeletal abnormalities. Half of affected individuals also experience photosensitivity to UV light. TTD is caused by mutations in one of three genes, ''ERCC2'', ''ERCC3'', or ''
GTF2H5 General transcription factor IIH subunit 5 is a protein that in humans is encoded by the ''GTF2H5'' gene. Function The ''GTF2H5(TTDA)'' gene encodes a small (71 amino acid) protein that stabilizes the multi-subunit transcription repair factor IIH ...
'', the first two of which are also linked to xeroderma pigmentosum. However, patients with TTD do not show a higher risk of developing skin cancer, in contrast to patients with XP. The three genes associated with TTD encode for XPB, XPD and p8/TTDA of the general transcription factor IIH (TFIIH) complex, which is involved in transcription and DNA damage repair. Mutations in one of these genes cause reduction of gene transcription, which may be involved in development (including
placental development Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...
), and thus may explain retardation in intellectual abilities, in some cases; these mutations also lead to reduction in DNA repair, causing photosensitivity. A form of TTD without photosensitivity also exists, although its mechanism is unclear. The '' MPLKIP'' gene has been associated with this form of TTD, although it accounts for only 20% of all known cases of the non-photosensitive form of TTD, and the function of its gene product is also unclear. Mutations in the ''TTDN1'' gene explain another 10% of non-photosensitive TTD. The function of the gene product of ''TTDN1'' is unknown, but the sex organs of individuals with this form of TTD often produce no hormones, a condition known as
hypogonadism Hypogonadism means diminished functional activity of the gonads—the testes or the ovaries—that may result in diminished production of sex hormones. Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estrogen ...
.


Defects in Lamin A/C

''Hutchinson–Gilford progeria syndrome'' (HGPS) and ''restrictive dermopathy'' (RD) are two PS caused by a defect in lamin A/C, which is encoded by the ''LMNA'' gene. Lamin A is a major nuclear component that determines the shape and integrity of the
nucleus Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA Nucle ...
, by acting as a
scaffold protein In biology, scaffold proteins are crucial regulators of many key signalling pathways. Although scaffolds are not strictly defined in function, they are known to interact and/or bind with multiple members of a signalling pathway, tethering them in ...
that forms a filamentous meshwork underlying the inner
nuclear envelope The nuclear envelope, also known as the nuclear membrane, is made up of two lipid bilayer membranes that in eukaryotic cells surround the nucleus, which encloses the genetic material. The nuclear envelope consists of two lipid bilayer membrane ...
, the membrane that surrounds the nucleus.


Hutchinson–Gilford progeria syndrome

''Hutchinson–Gilford progeria syndrome'' is an extremely rare developmental
autosomal dominant In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
condition, characterized by premature and accelerated aging (~7 times the normal rate) beginning at childhood. It affects 1 in ~4 million newborns; over 130 cases have been reported in the literature since the first described case in 1886. The mean age of diagnosis is ~3 years and the mean age of death is ~13 years. The cause of death is usually myocardial infarction, caused by the severe hardening of the arteries (arteriosclerosis). There is currently no treatment available. Individuals with HGPS typically appear normal at birth, but their growth is severely retarded, resulting in short stature, a very low body weight and delayed tooth eruption. Their facial/cranial proportions and facial features are abnormal, characterized by larger-than-normal eyes, a thin, beaked nose, thin lips, small chin and jaw (
micrognathia Micrognathism is a condition where the jaw is undersized. It is also sometimes called mandibular hypoplasia. It is common in infants, but is usually self-corrected during growth, due to the jaws' increasing in size. It may be a cause of abnorm ...
), protruding ears, scalp hair, eyebrows, and lashes,
hair loss Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarri ...
, large head, large
fontanelle A fontanelle (or fontanel) (colloquially, soft spot) is an anatomical feature of the infant human skull comprising soft membranous gaps ( sutures) between the cranial bones that make up the calvaria of a fetus or an infant. Fontanelles allow f ...
and generally appearing aged. Other features include skeletal alterations (osteolysis, osteoporosis), amyotrophy (wasting of muscle), lipodystrophy and skin atrophy (loss of subcutaneous tissue and fat) with sclerodermatous focal lesions, severe atherosclerosis and prominent scalp veins. However, the level of cognitive function, motor skills, and risk of developing cancer is not affected significantly. HGPS is caused by sporadic mutations (not inherited from parent) in the ''LMNA'' gene, which encodes for lamin A. Specifically, most HGPS are caused by a dominant, ''de novo'', point mutation p.G608G (GGC > GGT). This mutation causes a splice site within
exon An exon is any part of a gene that will form a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term ''exon'' refers to both the DNA sequence within a gene and to the corresponding sequen ...
11 of the pre-mRNA to come into action, leading to the last 150 base pairs of that exon, and consequently, the 50 amino acids near the C-terminus, being deleted. This results in a truncated lamin A precursor (a.k.a.
progerin Progerin (UniProt# P02545-6) is a truncated version of the lamin A protein involved in the pathology of Hutchinson–Gilford progeria syndrome. Progerin is most often generated by a sporadic single point nucleotide polymorphism c.1824 C>T (GGC -> GG ...
or LaminAΔ50). After being translated, a
farnesol Farnesol is a natural 15-carbon organic compound which is an acyclic sesquiterpene alcohol. Under standard conditions, it is a colorless liquid. It is hydrophobic, and thus insoluble in water, but miscible with oils. Farnesol is produced from 5- ...
is added to prelamin A using protein farnesyltransferase; this farnesylation is important in targeting lamin to the nuclear envelope, where it maintains its integrity. Normally, lamin A is recognized by ZMPSTE24 (FACE1, a
metalloprotease A metalloproteinase, or metalloprotease, is any protease enzyme whose catalytic mechanism involves a metal. An example is ADAM12 which plays a significant role in the fusion of muscle cells during embryo development, in a process known as myogen ...
) and cleaved, removing the farnesol and a few other amino acids. In the truncated lamin A precursor, this cleavage is not possible and the prelamin A cannot mature. When the truncated prelamin A is localized to the nuclear envelope, it will not be processed and accumulates, leading to "lobulation of the nuclear envelope, thickening of the nuclear lamina, loss of peripheral heterochromatin, and clustering of nuclear pores", causing the nucleus to lose its shape and integrity. The prelamin A also maintains the farnesyl and a methyl moiety on its C-terminal cysteine residue, ensuring their continued localization at the membrane. When this farnesylation is prevented using farnesyltransferase inhibitor (FTI), the abnormalities in nuclear shape are significantly reduced. HGPS is considered autosomal dominant, which means that only one of the two copies of the ''LMNA'' gene needs to be mutated to produce this phenotype. As the phenotype is caused by an accumulation of the truncated prelamin A, only mutation in one of the two genes is sufficient. At least 16 Other mutations in lamin A/C, or defects in the ''ZMPSTE24'' gene, have been shown to cause HGPS and other progeria-like symptoms, although these are less studied. Repair of DNA double-strand breaks can occur by one of two processes,
non-homologous end joining Non-homologous end joining (NHEJ) is a pathway that repairs double-strand breaks in DNA. NHEJ is referred to as "non-homologous" because the break ends are directly ligated without the need for a homologous template, in contrast to homology direct ...
(NHEJ) or
homologous recombination Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may ...
(HR). A-type
lamin Lamins, also known as nuclear lamins are fibrous proteins in type V intermediate filaments, providing structural function and transcriptional regulation in the cell nucleus. Nuclear lamins interact with inner nuclear membrane proteins to form t ...
s promote genetic stability by maintaining levels of proteins which have key roles in NHEJ and HR. Mouse cells deficient for maturation of prelamin A show increased DNA damage and chromosome aberrations and have increased sensitivity to DNA damaging agents. In HGPS, the inability to adequately repair DNA damages due to defective A-type lamin may cause aspects of premature aging (see
DNA damage theory of aging The DNA damage theory of aging proposes that aging is a consequence of unrepaired accumulation of naturally occurring DNA damage. Damage in this context is a DNA alteration that has an abnormal structure. Although both mitochondrial and nuclear ...
).


Restrictive dermopathy

''Restrictive dermopathy'' (RD), also called tight skin contracture syndrome, is a rare, lethal autosomal recessive perinatal
genodermatosis Genodermatosis is a hereditary skin disease with three inherited modes including single gene inheritance, multiple gene inheritance and chromosome inheritance. There are many different types of genodermatosis, the prevalence of genodermatosis rang ...
. Two known causes of RD are mutations in the ''LMNA'' gene, which lead to the production of truncated prelamin A precursor, and insertions in the ''ZMPSTE24'', which lead to a premature stop codon. Individuals with RD exhibit growth retardation starting in the
uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uter ...
, tight and rigid skin with erosions, prominent superficial
vasculature The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
and epidermal hyperkeratosis, abnormal facial features (small mouth, small pinched nose and micrognathia), sparse or absent eyelashes and eyebrows, mineralization defects of the skull, thin dysplastic clavicles, pulmonary hypoplasia and multiple joint contractures. Most affected individuals die in the uterus or are stillbirths, and liveborns usually die within a week.


Defects in FBN1

Patients with Marfan-progeroid-lipodystrophy syndrome typically exhibit congenital lipodystrophy and a neonatal progeroid appearance. Sometimes identified as having neonatal progeroid syndrome, the term is a misnomer since they do not exhibit accelerated aging. The condition is caused by mutations near the 3'-terminus of the ''
FBN1 Fibrillin-1 is a protein that in humans is encoded by the ''FBN1'' gene, located on chromosome 15. It is a large, extracellular matrix glycoprotein that serves as a structural component of 10-12 nm calcium-binding microfibrils. These microfib ...
'' gene.


A common cause for premature aging

Hutchinson–Gilford progeria syndrome, Werner syndrome, and Cockayne syndrome are the three genetic disorders in which patients have premature aging features. Premature aging also develops on some animal models which have genetic alterations. Although the patients with these syndromes and the animal models with premature aging symptoms have different genetic backgrounds, they all have abnormal structures of tissues/organs as a result of defective development. Misrepair-accumulation aging theory suggests that the abnormality of tissue structure is the common point between premature aging and normal aging. Premature aging is a result of Mis-construction during development as a consequence of gene mutations, whereas normal aging is a result of accumulation of Misrepairs for the survival of an organism. Thus the process of development and that of aging are coupled by Mis-construction and Mis-re-construction (Misrepair) of the structure of an organism.


Unknown causes


Wiedemann–Rautenstrauch syndrome

''Wiedemann–Rautenstrauch (WR) syndrome'', also known as ''neonatal progeroid syndrome'', is an autosomal recessive progeroid syndrome. More than 30 cases have been reported. Most affected individuals die by seven months of age, but some do survive into their teens. WR is associated with abnormalities in bone maturation, and lipids and hormone metabolism. Affected individuals exhibit intrauterine and postnatal growth retardation, leading to short stature and an aged appearance from birth. They have physical abnormalities including a large head (macrocephaly), sparse hair, prominent scalp veins, inward-folded eyelids, widened anterior fontanelles, hollow cheeks (malar hypoplasia), general loss of fat tissues under the skin, delayed tooth eruption, abnormal hair pattern, beaked noses, mild to severe intellectual disability and
dysmorphism A dysmorphic feature is an abnormal difference in body structure. It can be an isolated finding in an otherwise normal individual, or it can be related to a congenital disorder, genetic syndrome or birth defect. Dysmorphology is the study of dysm ...
. The cause of WR is unknown, although defects in DNA repair have been implicated.


Rothmund–Thomson syndrome

Classified as an
autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
defect, but the
pathology Pathology is the study of the causes and effects of disease or injury. The word ''pathology'' also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in ...
has still yet to be well researched.


Cancer

Some segmental progeroid syndromes, such as Werner syndrome (WS), Bloom syndrome (BS), Rothmund-Thomson syndromes (RTS) and combined xeroderma pigmentosa-Cockayne syndrome (XP-CS), are associated with an increased risk of developing cancer in the affected individual; two exceptions are Hutchinson–Gilford progeria (HGPS) and Cockayne syndrome.


Animal models

Within
animal models A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the working ...
for progeroid syndromes, early observations have detected abnormalities within overall mitochondrial function,
signal transduction Signal transduction is the process by which a chemical or physical signal is transmitted through a cell as a series of molecular events, most commonly protein phosphorylation catalyzed by protein kinases, which ultimately results in a cellula ...
between membrane receptors, and nuclear regulatory proteins.


Other

Alterations in lipid and carbohydrate metabolism, a triplet-repeat disorder (myotonic dystrophy) and an idiopathic disorder


Society and popular culture


People

Hayley Okines Hayley Leanne Okines (3 December 1997 – 2 April 2015) was an English author and activist who was a sufferer of the extremely rare aging disease progeria. She was known for spreading awareness of the condition. Although the average life e ...
was an English girl with classic progeria famed for her efforts in spreading awareness of the condition. She was featured in the media.
Lizzie Velásquez Elizabeth Anne Velásquez (; born March 13, 1989) is an American motivational speaker, activist, author, and YouTuber. She was born with an extremely rare congenital disease called Marfanoid–progeroid–lipodystrophy syndrome that, among o ...
is an American
motivational speaker A motivational speaker is a speaker who makes speeches intended to motivate or inspire an audience. Such speakers may attempt to challenge or transform their audiences. The speech itself is popularly known as a pep talk. Motivational speakers ca ...
who has a syndrome that resembles progeria, although the exact nature is unclear; it is now thought to be a form of neonatal progeroid syndrome. Velásquez is an advocate of anti-bullying. Jesper Sørensen is widely recognized in Denmark as the only child in
Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Danish Realm, Kingdom of Denmark ...
and
Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...
with progeria (as of 2008). His fame came about after a documentary in 2008 on TV 2 about Sørensen.


Literature

F. Scott Fitzgerald Francis Scott Key Fitzgerald (September 24, 1896 – December 21, 1940) was an American novelist, essayist, and short story writer. He is best known for his novels depicting the flamboyance and excess of the Jazz Age—a term he popularize ...
's 1922 short story ''The Curious Case of Benjamin Button'' is about a boy who was born with the appearance of a 70-year-old and who ages backwards. This short story is thought to be inspired by progeria. The description of the fictitious Smallweed family in the
Charles Dickens Charles John Huffam Dickens (; 7 February 1812 – 9 June 1870) was an English writer and social critic. He created some of the world's best-known fictional characters and is regarded by many as the greatest novelist of the Victorian e ...
' ''
Bleak House ''Bleak House'' is a novel by Charles Dickens, first published as a 20-episode serial between March 1852 and September 1853. The novel has many characters and several sub-plots, and is told partly by the novel's heroine, Esther Summerson, and ...
'' suggests the characters had progeria. Christopher Snow, the main character in
Dean Koontz Dean Ray Koontz (born July 9, 1945) is an American author. His novels are billed as Thriller (genre), suspense thrillers, but frequently incorporate elements of horror fiction, horror, fantasy, science fiction, Mystery fiction, mystery, and satir ...
's ''
Moonlight Bay Trilogy The ''Moonlight Bay Trilogy'' is an unfinished trilogy of three novels by Dean Koontz. They revolve around the mysterious events in Moonlight Bay, a fictitious Southern California town, that are investigated by the main character Christopher Snow ...
'', has xeroderma pigmentosum, as does Luke from the 2002 novel ''Going Out'' by
Scarlett Thomas Scarlett Thomas (born 5 July 1972 in Hammersmith) is an English author who writes contemporary postmodern fiction. She has published ten novels, including '' The End of Mr. Y'' and '' PopCo'', as well as the ''Worldquake'' series of children's ...
. In the visual novel ''
Chaos;Head ''Chaos;Head'' (stylized as ''ChäoS;HEAd'') is a 2008 science fiction visual novel video game developed by 5pb. and Nitroplus. It is the first game in the ''Science Adventure'' series. Following the original Windows release, the enhanced ver ...
'', the character Shogun eventually dies of a progeroid syndrome, and in its sequel ''
Chaos;Child ''Chaos;Child'' (stylized as ''ChäoS;Child'') is a visual novel video game developed by 5pb. It is the fourth main entry in the ''Science Adventure'' series, and a thematic sequel to ''Chaos;Head'' (2008). It was released in Japan in 2014 for Xb ...
'', more characters get this same fictional progeroid syndrome, which by then is called Chaos Child Syndrome.


Film

'' Paa'', a 2009 Indian comedy-drama film, features a protagonist, Auro (
Amitabh Bachchan Amitabh Bachchan (; born as Amitabh Shrivastav; 11 October 1942) is an Indian actor, film producer, television host, occasional playback singer and former politician known for his work in Hindi cinema. He is regarded as one of the most succe ...
), who has progeria. ''
Jack Jack may refer to: Places * Jack, Alabama, US, an unincorporated community * Jack, Missouri, US, an unincorporated community * Jack County, Texas, a county in Texas, USA People and fictional characters * Jack (given name), a male given name, ...
'' is a 1996 American comedy-drama film, in which the titular character (portrayed by
Robin Williams Robin McLaurin Williams (July 21, 1951August 11, 2014) was an American actor and comedian. Known for his improvisational skills and the wide variety of characters he created on the spur of the moment and portrayed on film, in dramas and come ...
) has Werner syndrome. '' Taiyou no Uta'', a 2006 Japanese film, features Kaoru Amane (portrayed by
Yui Yui may refer to: People * Yui (name), a Japanese name *Yui (singer) (born 1987), Japanese singer-songwriter, multi-instrumentalist, and actress * Yui people or Ibi, a Timucuan-speaking people in what now is Georgia, United States Places * Yui, Sh ...
), a 16-year-old girl has xeroderma pigmentosum.


See also

* DeSanctis–Cacchione syndrome, an extremely rare variant of xeroderma pigmentosum (XP) *
Dyskeratosis congenita Dyskeratosis congenita (DKC), also known as Zinsser-Engman-Cole syndrome, is a rare progressive congenital disorder with a highly variable phenotype. The entity was classically defined by the triad of abnormal skin pigmentation, nail dystrophy, and ...
, a rare progressive congenital disorder of the skin and bone marrow in some ways resembling progeria *
Fanconi anemia Fanconi anaemia (FA) is a rare genetic disease resulting in impaired response to DNA damage. Although it is a very rare disorder, study of this and other bone marrow failure syndromes has improved scientific understanding of the mechanisms of nor ...
, a rare genetic defect in a cluster of proteins responsible for DNA repair *
Li–Fraumeni syndrome Li–Fraumeni syndrome is a rare, autosomal dominant, hereditary disorder that predisposes carriers to cancer development. It was named after two American physicians, Frederick Pei Li and Joseph F. Fraumeni, Jr., who first recognized the syndrom ...
, a rare autosomal genetic disorder caused by defects in DNA repair * Nijmegen breakage syndrome, a rare autosomal recessive genetic disorder caused by defect(s) in the Double Holliday junction DNA repair mechanism * Nestor-Guillermo progeria syndrome, an extremely rare genetic disorder which is unique from other PS because of the absence of any cardiovascular abnormalities (which lead to premature death in cases where they are present)


References


Further reading

* * * *


External links


Hutchinson–Gilford Progeria Syndrome
described in GeneReviews™
NIH Office of Rare Diseases Research (ORDR)
- a
National Institutes of Health The National Institutes of Health, commonly referred to as NIH (with each letter pronounced individually), is the primary agency of the United States government responsible for biomedical and public health research. It was founded in the late ...
branch which coordinates and supports rare diseases research
Orphanet
a reference portal for information on rare diseases and orphan drugs {{Authority control Rare syndromes Aging-associated diseases Genetic diseases and disorders Senescence