A frameshift insertion in the cone cyclic nucleotide gated cation channel causes complete achromatopsia in a consanguineous family from a rural isolate |
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Authors: | Rojas Cecilia V María Lorena Santa Santos José Luis Cortés Fanny Alliende María Angélica |
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Institution: | INTA, Universidad de Chile, Casilla 138-11, Santiago, Chile. crojas@uec.inta.uchile.cl |
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Abstract: | Complete achromatopsia is genetically heterogeneous and segregates with mutations in CNGA3 or CNGB3 genes, which respectively encode for alpha- and beta-subunits of the cyclic-nucleotide-gated (CNG) cation channel expressed in cone photoreceptors. High incidence of the disease (1 in 60) was detected in a rural isolate in central Chile. We excluded previously reported mutations in a consanguineous kindred with five affected members. Genotype analysis with short tandem repeat polymorphic (STRP) markers provided evidence to search for the causative mutation in CNGB3. Two sequence variations, c.492_493insT and c.488A>G, flanking an adenosine (A(5)) repeat in exon 4 were identified. The frameshift mutation creates two consecutive stop codons in exon 5 that would induce premature translation termination. The severely truncated beta-subunit is likely to render a nonfunctional cone CNG channel and cause total colour blindness in this kindred. |
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