Purchase this article with an account.
K.L. Gunther, J. Neitz, M. Neitz; A Novel Missense Mutation in the S Cone Photopigment in a Male Who Made Tritan Errors on the Neitz Test of Color Vision . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1907.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: In an ongoing effort to identify new mutations that underlie inherited color vision deficiency, we screened 425 medical students for defects using the Neitz Test of Color Vision. One (#4041) student was unique in that he made errors on the two tritan symbols but made no other errors. To test the hypothesis that subject #4041 has a mutation in his S cone photopigment gene, his S cone photopigment genes were sequenced and compared to the sequence of the S opsin genes from 107 subjects with normal color vision. Three amino acid substitutions in the S opsin gene have previously been associated with tritanopia, which is a rare autosomal dominant color vision defect that is estimated to affect 1 in 10,000 people. Methods: The S cone photopigment gene from subject #4041 was amplified with the polymerase chain reaction, and the coding region was sequenced. A new mutation was found. The S cone opsin genes in 107 individuals with normal color vision were screened for this mutation using the Transgenomic WAVE-MD denaturing high performance liquid chromatography (dHPLC) system. Results: Subject #4041 was heterozygous for a single nucleotide change in exon 1 of his S cone opsin genes. The mutation leads to a substitution of proline for leucine at amino acid position 56 of the S opsin. This mutation was not detected by dHPLC in 107 subjects with normal color vision. Conclusions: Evidence indicating that substituting proline for leucine at amino acid position 56 of the S cone opsin causes a tritan defect include (i) all known amino acid substitutions in S opsin cause tritanopia, (ii) a proline at position 56 is expected to introduce a bend in helix I that is likely to disrupt photopigment function, (iii) alignment of all members of the rhodopsin family of G-protein coupled receptors in the GPCR database reveal that this amino acid position is highly conserved, with 76% of the 137 opsins in the database having leucine, and 24% having either valine, isoleucine or methionine; no member of this family has proline at this position, (iv) subject #4041 made only tritan errors on the Neitz Test of Color Vision, and (v) the substitution was not found in 107 individuals with normal color vision.
This PDF is available to Subscribers Only