Study of the involvement of the RGR, CRPB1, and CRB1 genes in the pathogenesis of autosomal recessive retinitis pigmentosa
- 1Servei de Genética, Hospital de la Santa Creu I Sant Pau, Barcelona, Spain
- 2Servicio de Genética, Fundación Jiménez Díaz, Madrid, Spain
- 3Servicio de Oftalmologia, Fundación Jiménez Díaz, Madrid, Spain
- 4Servei de Genética, Hospital Son Dureta, Palma de Mallorca
- 5Servei d’Oftalmologia, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
- Correspondence to: Dr M Baiget, Servei de Genética, Hospital de la Santa Creu i Sant Pau, Pare Claret 167, 08025 Barcelona, Spain;
Retinitis pigmentosa (RP), which occurs in about 1 in 3000-7000 people in Spain, is inherited in an autosomal dominant manner in 12% of cases, in an autosomal recessive way in 39%, and in an X linked manner in 4% of cases.1 This leaves 41% of RP cases with a simplex form and 4% in which the transmission pattern is unclear.
The different genes that have been implicated in retinal degeneration are known or assumed to be expressed in the photoreceptor cells of the retina or in the retinal pigment epithelium (RPE). The large number of RP genes identified can be grouped into a number of functional classes: (1) proteins of the visual cascade, (2) proteins of the visual cycle, (3) photoreceptor cell transcription factors, (4) proteins related to catabolic processes, and (5) genes of unknown function.
Previous studies performed in autosomal recessive retinitis pigmentosa (ARRP) Spanish families have shown that genes coding for recoverin,2 rhodopsin, rod outer segment membrane protein and peripherin/RDS,3 S antigen and the gamma subunit of rod cGMP-phosphodiesterase,4 interstitial retinol binding protein,5 the alpha subunit of rod cGMP-phosphodiesterase and NRL,6 and the retinaldehyde binding protein7 do not play a role in this disorder. However, mutations in the beta subunit of the rod cGMP-phosphodiesterase gene,8–11 in the ATP binding cassette receptor gene,12 in the TULP1 gene,13 in the alpha subunit of the rod cGMP gated channel,14 and in the USH2A gene15 have been detected in a small percentage of Spanish ARRP families. These data indicate that other genes play a part in the degeneration process of the retina in the remaining families.
We analysed the involvement of three additional genes, the RPE retinal G protein coupled receptor (RGR), the cellular retinol binding protein (CRBP1), and …