Deletion of the X-linked opsin gene array locus control region (LCR) results in disruption of the cone mosaic

Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, WI 53226, United States.
Vision research (Impact Factor: 2.38). 09/2010; 50(19):1989-99. DOI: 10.1016/j.visres.2010.07.009
Source: PubMed

ABSTRACT Blue cone monochromacy (BCM) is an X-linked condition in which long- (L) and middle- (M) wavelength-sensitive cone function is absent. Due to the X-linked nature of the condition, female carriers are spared from a full manifestation of the associated defects but can show visual symptoms, including abnormal cone electroretinograms. Here we imaged the cone mosaic in four females carrying an L/M array with deletion of the locus control region, resulting in an absence of L/M opsin gene expression (effectively acting as a cone opsin knockout). On average, they had cone mosaics with reduced density and disrupted organization compared to normal trichromats. This suggests that the absence of opsin in a subset of cones results in their early degeneration, with X-inactivation the likely mechanism underlying phenotypic variability in BCM carriers.

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