Retinitis Pigmentosa 49
A number sign (#) is used with this entry because retinitis pigmentosa-49 (RP49) is caused by homozygous or compound heterozygous mutation in the alpha-1 cyclic nucleotide-gated channel gene (CNGA1; 123825) on chromosome 4p12.
For a phenotypic description and a discussion of genetic heterogeneity of retinitis pigmentosa, see 268000.
Molecular GeneticsIn a screen of 267 patients with autosomal dominant or autosomal recessive retinitis pigmentosa, Dryja et al. (1995) identified 4 probands with autosomal recessive RP carrying mutations in the CNCG1 (CNGA1) gene. Five mutant sequences cosegregated with the disease among 4 unrelated families with autosomal recessive RP. In 3 of the families, the affected individuals were either homozygous for a mutation or were compound heterozygotes. Unaffected relatives either had no mutation or were heterozygote carriers for CNGA1 mutations. In the fourth family, a premature termination mutation (123825.0001) was present heterozygously in 2 affected sisters and in their unaffected father. The authors considered it possible that mutation in another gene on the maternal allele combined with the CNGA1 defect (digenic inheritance) contributed to the phenotype. In addition, 1 missense mutation (123825.0003) was found in heterozygosity in a patient segregating autosomal dominant RP; this patient also carried a rhodopsin mutation present in other affected members of the family, and this mutation was determined to be the cause of the phenotype.