PubMed ID: 27447086
Author(s): Patterson EJ, Wilk M, Langlo CS, Kasilian M, Ring M, Hufnagel RB, Dubis AM, Tee JJ, Kalitzeos A, Gardner JC, Ahmed ZM, Sisk RA, Larsen M, Sjoberg S, Connor TB, Dubra A, Neitz J, Hardcastle AJ, Neitz M, Michaelides M, Carroll J. Cone photoreceptor structure in patients with X-linked cone dysfunction and red-green color vision deficiency. Invest Ophthalmol Vis Sci. 2016 Jul 1;57(8):3853-63. doi: 10.1167/iovs.16-19608. PMID 27447086
Journal: Investigative Ophthalmology & Visual Science, Volume 57, Issue 8, Jul 2016
PURPOSE Mutations in the coding sequence of the L and M opsin genes are often associated with X-linked cone dysfunction (such as Bornholm Eye Disease, BED), though the exact color vision phenotype associated with these disorders is variable. We examined individuals with L/M opsin gene mutations to clarify the link between color vision deficiency and cone dysfunction.
METHODS We recruited 17 males for imaging. The thickness and integrity of the photoreceptor layers were evaluated using spectral-domain optical coherence tomography. Cone density was measured using high-resolution images of the cone mosaic obtained with adaptive optics scanning light ophthalmoscopy. The L/M opsin gene array was characterized in 16 subjects, including at least one subject from each family.
RESULTS There were six subjects with the LVAVA haplotype encoded by exon 3, seven with LIAVA, two with the Cys203Arg mutation encoded by exon 4, and two with a novel insertion in exon 2. Foveal cone structure and retinal thickness was disrupted to a variable degree, even among related individuals with the same L/M array.
CONCLUSIONS Our findings provide a direct link between disruption of the cone mosaic and L/M opsin variants. We hypothesize that, in addition to large phenotypic differences between different L/M opsin variants, the ratio of expression of first versus downstream genes in the L/M array contributes to phenotypic diversity. While the L/M opsin mutations underlie the cone dysfunction in all of the subjects tested, the color vision defect can be caused either by the same mutation or a gene rearrangement at the same locus.