This report describes retinitis pigmentosa 12 (RP12), which is a subtype of retinitis pigmentosa; RP12 exhibits autosomal recessive inheritance. The human gene implicated in this disease is CRB1, which plays a role in the morphogenesis of photoreceptor cells. CRB1 is also implicated in other diseases associated with retinal degeneration (MIM:604210). There is a single fly gene, crb, that is orthologous to both CRB1 and CRB2, and for which classical amorphic and hypomorphic alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated. See also the report for 'retinal disease, CRB1-related' (FBhh0000572) for additional information on experimental results using Drosophila models of this and related diseases.
Experiments characterizing mutations in the fly gene analogous to variants implicated in human retinal disease include several implicated in retinitis pigmentosa 12. Variant(s) implicated in human disease tested (as analogous mutation in fly gene): C749W in the fly crb gene (corresponds to C250W in the human CRB1 gene, implicated in RP12); T1283M in the fly crb gene (corresponds to T745M in the human CRB1 gene, implicated in RP12); N1486S in the fly crb gene (corresponds to N894S in the human CRB1 gene, implicated in RP12); C1540Y in the fly crb gene (corresponds to C948Y in the human CRB1 gene, implicated in RP12 and Leber congenital amaurosis 8).
[updated Apr. 2018 by FlyBase; FBrf0222196]
Retinitis pigmentosa (RP) refers to a heterogeneous group of inherited ocular diseases that result in a progressive retinal degeneration affecting 1 in 3,000 to 5,000 people (Veltel et al., 2008; pubmed:18376416). Symptoms include night blindness, the development of tunnel vision, and slowly progressive decreased central vision starting at approximately 20 years of age. [from MIM:268000; 2016.03.07]
The rate and extent of disease progression vary markedly among RP patients, in some cases, even within the same family. [from MIM:600059; 2020.08.04]
[RETINITIS PIGMENTOSA 12; RP12](https://omim.org/entry/600105)
[CRUMBS CELL POLARITY COMPLEX COMPONENT 1; CRB1](https://omim.org/entry/604210)
See general description above.
Retinitis pigmentosa 12 is caused by homozygous or compound heterozygous mutations in the crumbs 1, cell polarity complex component (CRB1) gene. [from MIM:600105; 2016.03.09]
The ortholgous crb gene in Drosophila plays a role in establishing apical-basal polarity in epithelial cells, including in differentiating photoreceptors.
The CRB1 protein localizes to the inner segment of mammalian photoreceptors in the retina and appears to play a role in photoreceptor morphogenesis. [from MIM:604210; 2016.03.15]
Many to one: 2 human to 1 Drosophila; the second orthologous human gene is CRB2.
Moderate-scoring ortholog of human CRB1 (reciprocal best hit) and CRB2 (1 Drosophila to 2 human). Dmel\crb shares 28-30% identity and 40-43% similarity with the human genes. In invertebrates, the orthologous genes are longer than in vertebrates, with additional laminin and EGF-like domains.