Cone-rod homeobox protein is a
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...
that in humans is encoded by the ''CRX''
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 ...
.
Function
The protein encoded by this gene is a photoreceptor-specific transcription factor which plays a role in the differentiation of photoreceptor cells. This homeodomain protein is necessary for the maintenance of normal cone and rod function.
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, mi ...
in this gene are associated with photoreceptor degeneration,
Leber's congenital amaurosis
Leber congenital amaurosis (LCA) is a rare inherited eye disease that appears at birth or in the first few months of life.
It affects about 1 in 40,000 newborns. LCA was first described by Theodor Leber in the 19th century. It should not be co ...
type III and the autosomal dominant
cone-rod dystrophy
A cone dystrophy is an inherited ocular disorder characterized by the loss of cone cells, the photoreceptors responsible for both central and color vision.
Presentation
The most common symptoms of cone dystrophy are vision loss (age of onset r ...
2. Several alternatively spliced transcript variants of this gene have been described, but the full-length nature of some variants has not been determined.
Mammalian CRX encodes a 299 amino acid protein containing a DNA binding
homeodomain
A homeobox is a DNA sequence, around 180 base pairs long, that regulates large-scale anatomical features in the early stages of embryonic development. For instance, mutations in a homeobox may change large-scale anatomical features of the full-g ...
(HD) near its N-terminus followed by glutamine rich (Gln), and basic amino acid regions, then a C-terminal
transactivation domain
The transactivation domain or trans-activating domain (TAD) is a transcription factor scaffold domain which contains binding sites for other proteins such as transcription coregulators. These binding sites are frequently referred to as activation ...
(AD).
While structural biochemistry has demonstrated that the CRX HD adopts a canonical homeodomain protein fold, the AD is predicted to be flexible and disordered. The structural attributes of the CRX AD have yet to be solved.
Evolution
''CRX'' is a divergent duplicate of
OTX produced during the 2 rounds of
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
whole genome duplication.
In the
eutherian
Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials.
Eutherians are distinguished from noneutherians by various phenotypic tra ...
mammals
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...
, ''CRX'' has again duplicated by tandem
gene duplication
Gene duplication (or chromosomal duplication or gene amplification) is a major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. ...
, with six ancestral duplicates, which are collectively referred to as ETCHbox genes.
References
Further reading
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External links
GeneReviews/NCBI/NIH/UW entry on Retinitis Pigmentosa Overview*
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{{Transcription factors, g3
Transcription factors