Cone-rod homeobox protein is a protein that in humans is encoded by the CRXgene.[5][6][7]
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 this gene are associated with photoreceptor degeneration, Leber's congenital amaurosis type III and the autosomal dominant cone-rod dystrophy 2. Several alternatively spliced transcript variants of this gene have been described, but the full-length nature of some variants has not been determined.[7]
Mammalian CRX encodes a 299 amino acid protein containing a DNA binding homeodomain (HD) near its N-terminus followed by glutamine rich (Gln), and basic amino acid regions, then a C-terminal transactivation domain (AD).[8] 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.[9]
Evolution
CRX is a divergent duplicate of OTX produced during the 2 rounds of vertebrate whole genome duplication.[10]
In the eutherianmammals, CRX has again duplicated by tandem gene duplication, with six ancestral duplicates, which are collectively referred to as ETCHbox genes.[11]
Paunescu K, Preising MN, Janke B, Wissinger B, Lorenz B (Jul 2007). "Genotype-phenotype correlation in a German family with a novel complex CRX mutation extending the open reading frame". Ophthalmology. 114 (7): 1348–1357.e1. doi:10.1016/j.ophtha.2006.10.034. PMID17320181.
Evans K, Fryer A, Inglehearn C, Duvall-Young J, Whittaker JL, Gregory CY, et al. (Feb 1994). "Genetic linkage of cone-rod retinal dystrophy to chromosome 19q and evidence for segregation distortion". Nature Genetics. 6 (2): 210–3. doi:10.1038/ng0294-210. PMID8162077. S2CID333926.
Bessant DA, Payne AM, Mitton KP, Wang QL, Swain PK, Plant C, et al. (Apr 1999). "A mutation in NRL is associated with autosomal dominant retinitis pigmentosa". Nature Genetics. 21 (4): 355–6. doi:10.1038/7678. PMID10192380. S2CID28621258.
Yanagi Y, Masuhiro Y, Mori M, Yanagisawa J, Kato S (Mar 2000). "p300/CBP acts as a coactivator of the cone-rod homeobox transcription factor". Biochemical and Biophysical Research Communications. 269 (2): 410–4. doi:10.1006/bbrc.2000.2304. PMID10708567.
Koenekoop RK, Loyer M, Dembinska O, Beneish R (Mar 2002). "Visual improvement in Leber congenital amaurosis and the CRX genotype". Ophthalmic Genetics. 23 (1): 49–59. doi:10.1076/opge.23.1.49.2200. PMID11910559. S2CID21536673.
Nakamura M, Ito S, Miyake Y (Sep 2002). "Novel de novo mutation in CRX gene in a Japanese patient with leber congenital amaurosis". American Journal of Ophthalmology. 134 (3): 465–7. doi:10.1016/S0002-9394(02)01542-8. PMID12208271.
Lines MA, Hébert M, McTaggart KE, Flynn SJ, Tennant MT, MacDonald IM (Oct 2002). "Electrophysiologic and phenotypic features of an autosomal cone-rod dystrophy caused by a novel CRX mutation". Ophthalmology. 109 (10): 1862–70. doi:10.1016/S0161-6420(02)01187-9. PMID12359607.
Hodges MD, Vieira H, Gregory-Evans K, Gregory-Evans CY (Nov 2002). "Characterization of the genomic and transcriptional structure of the CRX gene: substantial differences between human and mouse". Genomics. 80 (5): 531–42. doi:10.1016/S0888-7543(02)96854-0. PMID12408971.
