Abstract

Complete achromatopsia is a rare autosomal recessively inherited disease characterized by total colour blindness. The disease is genetically heterogeneous and in about 75% of affected individuals it segregates with mutations in CNGA3 or CNGB3 genes, which respectively encode for the alpha and beta subunits of the cGMP-gated cation channel expressed in cone photoreceptors (OMIM #262300 and #216900). We evaluated a Chilean consanguineous kindred affected with complete achromatopsia in which none of the previously reported mutations were detected. Linkage analysis was carried out with microsatellite markers flanking CNGA3 gene and CNGB3 gene at 2q11-q12 and 8q21-q22 respectively, in order to target the search for the disease-causing mutation to the appropriate candidate gene. LOD score analysis and uncertainty analysis would indicate a higher-support for the presence of a mutation located in the CNGB3 gene (multipoint LOD score of 1.67) rather than in CNGA3 gene (multipoint LOD score of 0.77).