Analysis of L-cone/M-cone visual pigment gene arrays in Japanese males with protan color-vision deficiency

The L-cone/M-cone visual pigment gene arrays were analyzed in 125 Japanese males with protan color-vision deficiency. Arrays were successfully determined in 62/65 subjects with protanopia and 57/60 protanomaly subjects. Among the 62 protanopia subjects, 48 (77%) had an array consisting of a single 5' L-M hybrid gene (PS-array) or a 5' L-M hybrid gene followed by an M gene(s) that was structurally identical to the hybrid gene (PI-array). In the remaining 14 subjects, 11 had an array consisting of a 5' L-M hybrid gene followed by an M gene(s) that was structurally different from the hybrid gene (PD-array) and 3 subjects had an apparently normal array consisting of a single L gene followed by an M gene(s) (PN-array). In the 11 subjects with the PD-array, subject A67 had an 11 bp-deletion in exon 3 of the downstream genes and 6 had an A-71C substitution in the second gene of the array. In the 3 subjects with the PN-array, subject A289 had a missense mutation (Pro231Leu) in exon 4 of the L gene. When the function of the missense mutation was studied by in vitro reconstitution of visual pigments, it was found to be deleterious to both cone opsin and rhodopsin. Among the 57 protanomaly subjects, 49 (86%) had the PD-array, but 25 subjects had a difference only in exon 2 between the first and downstream genes that suggested a contribution of exon 2-encoded difference in the M pigment to color-discrimination. In the remaining 8 subjects, 2 had the PS-array, 2 had the PI-array and the other 4, including subject A89 with a missense mutation (Glu338Gly) in the L gene, had the PN-array. Genotype-phenotype relationships in protan color-vision deficiency are discussed.