This report describes cone-rod dystrophy 2 (CRD2 or CORD2), which is a subtype of cone-rod dystrophy; CRD2 exhibits autosomal dominant inheritance. The human gene implicated in this disease is CRX (cone-rod homeobox) gene, which encodes a transcription factor required for development and maintenance of photoreceptor cells. CRX is also implicated in other diseases associated with retinal degeneration (MIM:602225; MIM:268000). See the report for 'retinal disease, CRX-related' (FBhh0000567) for information on experimental results using Drosophila models of this and related diseases.
Variant(s) implicated in human disease tested (as transgenic human gene, CRX): the E80A variant form has been introduced into flies. This specific variant is associated with CRD2.
[updated Jul. 2017 by FlyBase; FBrf0222196]
Cone-rod dystrophy (CRD or CORD) is among a group of diseases described as hereditary cone disorders (Roosing, et al., 2014; pubmed:24857951).
In contrast to typical retinitis pigmentosa (RP), which results from the primary loss in rod photoreceptors, later followed by secondary loss in cone photoreceptors, cone-rod dystrophies (CRDs) exhibit the opposite sequence of events. The clinical course of CRDs is generally more severe and rapid than that of RPs, leading to earlier legal blindness and disability. (Hamel, 2007; pubmed:17270046).
Cone-rod dystrophy characteristically leads to early impairment of vision. An initial loss of color vision and of visual acuity is followed by nyctalopia (night blindness) and loss of peripheral visual fields. In extreme cases, these progressive symptoms are accompanied by widespread, advancing retinal pigmentation and chorioretinal atrophy of the central and peripheral retina (Moore, 1992; pubmed:1583653). [from MIM:120970; 2017.06.30]
[CONE-ROD DYSTROPHY 2; CORD2](https://omim.org/entry/120970)
[CONE-ROD HOMEOBOX-CONTAINING GENE; CRX](https://omim.org/entry/602225)
Cone-rod dystrophy 2 (CORD2) is caused by heterozygous mutation in the CRX gene. [from MIM:120970; 2017.06.30]
Many to one: 3 human to one Drosophila; the other human genes are OTX1 and OTX2.
Low- to moderate-scoring ortholog of human genes OTX1, OTX2, and CRX (1 Drosophila to 3 human); Dmel\oc shars 30-36% identity and 40-45% similarity with the human genes.
