8p23.1 duplication syndrome is a 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 ...

caused by a

duplication Duplication, duplicate, and duplicator may refer to: Biology and genetics * Gene duplication, a process which can result in free mutation * Chromosomal duplication, which can cause Bloom and Rett syndrome * Polyploidy, a phenomenon also known ...

of a region from human

chromosome 8 Chromosome 8 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 8 spans about 145 million base pairs (the building material of DNA) and represents between 4.5 and 5.0% of the total DNA ...

. This duplication syndrome has an estimated prevalence of 1 in 64,000 births and is the reciprocal of the 8p23.1 deletion syndrome. The 8p23.1 duplication is associated with a variable

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 ...

including one or more of

speech delay Speech delay, also known as alalia, refers to a delay in the development or use of the mechanisms that produce speech. Speech – as distinct from language – is the actual process of making sounds, using such organs and structures as the lungs, ...

developmental delay Global developmental delay is an umbrella term used when children are significantly delayed in their cognitive and physical development. It can be diagnosed when a child is delayed in one or more milestones, categorised into motor skills, speech, c ...

, mild dysmorphism, with prominent forehead and arched eyebrows, and

congenital heart disease A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital heart defect is classed as a cardiovascular ...

(CHD).

Presentation

The phenotypic data on 11 patients indicated that cases are not always ascertained for CHD but that CHD was the most common single feature found in 6 out of 11 individuals. Developmental delay and/or learning difficulties were found in 5 out of 11 cases, but one prenatal case was developing normally at 15 months of age (Case 1,). Three other prenatal cases could not yet be reliably assessed. A variable degree of facial

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 ...

was present in 5 out of 11 individuals. Partial toe

syndactyly Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and diprotodontia, but is an unusual condition in humans. The term is from Greek σύν, ''syn'' 'together' and δάκ� ...

has been found in one mother and son

diad Within the muscle tissue of animals and humans, contraction and relaxation of the muscle cells (myocytes) is a highly regulated and rhythmic process. In cardiomyocytes, or cardiac muscle cells, muscular contraction takes place due to movement at a ...

and adrenal anomalies in two

proband In medical genetics and other medical fields, a proband, proposito (male proband), or proposita (female proband)Bennett, RL. The Language of the Pedigree. In: ''The Practical Guide to the Genetic Family History''. Wiley-Liss. is a particular subjec ...

s but not in the duplicated mother of one of them. The phenotype is compatible with independent adult life with varying degrees of support. Duplication of the

GATA4 Transcription factor GATA-4 is a protein that in humans is encoded by the ''GATA4'' gene. Function This gene encodes a member of the GATA family of zinc finger transcription factors. Members of this family recognize the GATA motif which is pr ...

transcription factor () is believed to underlie the congenital heart disease and other genes, common to the duplication and deletion syndromes, can be regarded as candidates for the 8p23.1 duplication syndrome. These include the

SOX7 SRY-box 7 is a protein that in humans is encoded by the SOX7 gene. Function This gene encodes a member of the SOX (SRY-related HMG-box) family of transcription factors involved in the regulation of embryonic development and in the determinat ...

transcription factor () for both CHD and developmental delay and the

TNKS Tankyrase, also known as tankyrase 1, is an enzyme that in humans is encoded by the ''TNKS'' gene. It inhibits the binding of TERF1 to telomeric DNA. Tankyrase attracts substantial interest in cancer research through its interaction with AXIN1 a ...

gene () for behavioural difficulties. The

diaphragmatic hernia Diaphragmatic hernia is a defect or hole in the diaphragm that allows the abdominal contents to move into the chest cavity. Treatment is usually surgical. Types * Congenital diaphragmatic hernia ** Morgagni's hernia ** Bochdalek hernia * Hiatal h ...

found in the 8p23.1 deletion syndrome has not been found in the 8p23.1 duplication syndrome to date. The duplication may be associated with copy number changes of the adjacent

olfactory receptor Olfactory receptors (ORs), also known as odorant receptors, are chemoreceptors expressed in the cell membranes of olfactory receptor neurons and are responsible for the detection of odorants (for example, compounds that have an odor) which give ri ...

defensin Defensins are small cysteine-rich cationic proteins across cellular life, including vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, ...

repeats (ORDRs) that predispose to the 8p23.1 deletion and duplication syndromes. High total copy numbers of these repeats have been associated with predisposition to

psoriasis Psoriasis is a long-lasting, noncontagious autoimmune disease characterized by raised areas of abnormal skin. These areas are red, pink, or purple, dry, itchy, and scaly. Psoriasis varies in severity from small, localized patches to complete ...

and low copy number with predisposition to

Crohn's disease Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea (which may be bloody if inflammation is severe), fever, abdominal distension ...

Genetics

The duplication includes ~3.75 Mb between the distal and proximal ORDRs at either end of band 8p23.1. The copy number of the adjacent repeats may also be altered. The 8p23.1 duplication syndrome cannot be distinguished using conventional cytogenetics from high level copy number variation of the repeats themselves. Both de novo cases and families with transmitted duplications from parents of both sex are known. The duplication is believed to arise de novo as a result of

non-allelic homologous recombination Non-allelic homologous recombination (NAHR) is a form of homologous recombination that occurs between two lengths of DNA that have high sequence similarity, but are not alleles. It usually occurs between sequences of DNA that have been previously ...

(NAHR) between the proximal and distal ORDRs. NAHR is also thought to give rise to the reciprocal microdeletion syndrome, the polymorphic inversion between the ORDRs and a variety of other large scale abnormalities involving the short arm of chromosome 8.

Diagnosis

Phenotypes

References

External links