International Union of Pharmacology. LI. Nomenclature and structure-function relationships of cyclic nucleotide-regulated channels.
Hofmann F
et al.
Pharmacol Rev 2005 Dec;57(4)455-462
Hofmann F, Biel M, Kaupp UB.
Pharmacol Rev 2005 Dec;57(4)455-462
Mutations in the CNGB3 gene encoding the beta-subunit of the cone photoreceptor cGMP-gated channel are responsible for achromatopsia (ACHM3) linked to chromosome 8q21.
Kohl S
et al.
Hum Mol Genet 2000 Sep;9(14)2107-2116
Kohl S, Baumann B, Broghammer M, Jägle H, Sieving P, Kellner U, Spegal R, Anastasi M, Zrenner E, Sharpe LT, Wissinger B.
Hum Mol Genet 2000 Sep;9(14)2107-2116
Abstract: Achromatopsia is an autosomal recessive disorder featuring total colour blindness, photophobia, reduced visual acuity and nystagmus. While mutations in the CNGA3 gene on chromosome 2q11 are responsible for achromatopsia in a subset of patients, previous linkage studies have localized another achromatopsia locus, ACHM3, on chromosome 8q21. Using achromatopsia families in which CNGA3 mutations have been excluded, we refined the ACHM3 locus to a 3.7 cM region enclosed by markers D8S1838 and D8S273. Two yeast artificial chromosome (YAC) contigs covering nearly the entire ACHM3 interval were constructed. Database searches with YAC content sequences identified two overlapping high throughput genomic sequencing phase (HTGS) entries which contained sequences homologous to the murine cng6 gene encoding the putative beta-subunit of the cone photoreceptor cGMP-gated channel. Using RT-PCR and RACE, we identified and cloned the human cDNA homologue, designated CNGB3, which encodes an 809 amino acid polypeptide. Northern blot analysis revealed a major transcript of approximately 4.4 kb specifically expressed in the retina. The human CNGB3 gene consists of 18 exons distributed over approximately 200 kb of genomic sequence. Analysis of the CNGB3 gene in achromats revealed six different mutations including a missense mutation (S435F), two stop codon mutations (R203X and E336X), a 1 bp and an 8 bp deletion (1148delC and 819-826del) and a putative splice site mutation of intron 13. The 1148delC mutation was identified recurrently in several families, and in total was present on 11 of 22 disease chromosomes segregating in our families.
Genetic basis of total colourblindness among the Pingelapese islanders.
Sundin OH
et al.
Nat Genet 2000 Jul;25(3)289-293
Sundin OH, Yang JM, Li Y, Zhu D, Hurd JN, Mitchell TN, Silva ED, Maumenee IH.
Nat Genet 2000 Jul;25(3)289-293
Abstract: Complete achromatopsia is a rare, autosomal recessive disorder characterized by photophobia, low visual acuity, nystagmus and a total inability to distinguish colours. In this disease, cone photoreceptors, the retinal sensory neurons mediating colour vision, seem viable but fail to generate an electrical response to light. Achromatopsia, or rod monochromatism, was first mapped to 2p11-2q12 (MIM 216900; ref. 3), where it is associated with missense mutations in CNGA3 (ref. 4). CNGA3 encodes the alpha-subunit of the cone cyclic nucleotide-gated cation channel, which generates the light-evoked electrical responses of cone photoreceptors. A second locus at 8q21-q22 has been identified among the Pingelapese islanders of Micronesia, who have a high incidence of recessive achromatopsia (MIM 262300). Here we narrow the achromatopsia locus to 1.4 cM and show that Pingelapese achromatopsia segregates with a missense mutation at a highly conserved site in CNGB3, a new gene that encodes the beta-subunit of the cone cyclic nucleotide-gated cation channel. Two independent frameshift deletions establish that achromatopsia is the null phenotype of CNGB3. Combined with earlier findings, our results demonstrate that both alpha- and beta-subunits of the cGMP-gated channel are essential for phototransduction in all three classes of cones.
