Three visual pigments mediate trichromatic color vision in humans, Old World monkeys and apes. Genes that are nearly identical encode the middle- and long-wavelength sensitive pigments, abbreviated M and L, respectively. The M and L genes lie in a head-to-tail tandem array on the X-chromosome and were produced by a gene duplication event that is estimated to have occurred in the primate lineage about 35-60 million years ago. The short-wavelength sensitive pigment (S) is encoded by an autosome, and is estimated to have diverged from the ancestral M/L gene about 800-1 100 million years ago. The vast majority of cones in human and primate retina are either M or L cones, with only about 7 percent of cones being S. Among the L and M cones, each cell exclusively expresses only one pigment gene from the X-chromosome array. There are two fundamentally important unsolved mysteries regarding expression of the X-linked visual pigment genes that are the focus of this grant. First, do the M and L cones represent two distinct cell types, so that an M cone specific mechanism directs expression of M pigment, and an L cone specific mechanism directs expression of L pigment? In this scenario, the M and L cones are uniquely different, and the fact that they express different pigments is secondary to these other differences. Or, are the M and L cones one cell type in which there is a stochastic process that directs mutually exclusive expression of one of the X-chromosome pigment genes? In this scenario, the identity of the gene chosen for expression determines whether the cone will be an M or an L cone. The second mystery is, what determines which of the genes from an individual array are expressed? Recent evidence suggests that in arrays with 3 genes, the last gene in the array (3' most) is not expressed. But what about arrays with 4 genes, is the third gene expressed? Solving these two mysteries will have profound impact on our understanding of the fundamental biological processes that determine the organization of the photoreceptor mosaic, and of how neural circuits are wired to extract color information at the first synapse. Towards solving these mysteries we propose the following 4 specific aims: 1) To characterize the expression pattern of downstream genes, 2) To test the model for the mechanism that produces the high degree of L and M gene sequence polymorphism in humans implied from the observed expression pattern of downstream genes, 3) To conduct developmental and comparative studies to test the stochastic model; 4) To develop innovative models for directly testing the stochastic model.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY009620-13
Application #
6844634
Study Section
Special Emphasis Panel (ZRG1-SSS-R (02))
Program Officer
Chin, Hemin R
Project Start
1992-09-30
Project End
2007-01-31
Budget Start
2005-02-01
Budget End
2006-01-31
Support Year
13
Fiscal Year
2005
Total Cost
$464,919
Indirect Cost
Name
Medical College of Wisconsin
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
937639060
City
Milwaukee
State
WI
Country
United States
Zip Code
53226
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Davidoff, Candice; Neitz, Maureen; Neitz, Jay (2016) Genetic Testing as a New Standard for Clinical Diagnosis of Color Vision Deficiencies. Transl Vis Sci Technol 5:2
Neitz, Maureen; Neitz, Jay (2014) Curing color blindness--mice and nonhuman primates. Cold Spring Harb Perspect Med 4:a017418
Greenwald, Scott H; Kuchenbecker, James A; Roberson, Daniel K et al. (2014) S-opsin knockout mice with the endogenous M-opsin gene replaced by an L-opsin variant. Vis Neurosci 31:25-37
McClements, Michelle; Davies, Wayne I L; Michaelides, Michel et al. (2013) Variations in opsin coding sequences cause x-linked cone dysfunction syndrome with myopia and dichromacy. Invest Ophthalmol Vis Sci 54:1361-9
McClements, Michelle; Davies, Wayne I L; Michaelides, Michel et al. (2013) X-linked cone dystrophy and colour vision deficiency arising from a missense mutation in a hybrid L/M cone opsin gene. Vision Res 80:41-50
Carroll, Joseph; Dubra, Alfredo; Gardner, Jessica C et al. (2012) The effect of cone opsin mutations on retinal structure and the integrity of the photoreceptor mosaic. Invest Ophthalmol Vis Sci 53:8006-15
Baraas, Rigmor C; Hagen, Lene A; Dees, Elise W et al. (2012) Substitution of isoleucine for threonine at position 190 of S-opsin causes S-cone-function abnormalities. Vision Res 73:1-9
Neitz, Jay; Neitz, Maureen (2011) The genetics of normal and defective color vision. Vision Res 51:633-51
Carroll, Joseph; Rossi, Ethan A; Porter, Jason et al. (2010) Deletion of the X-linked opsin gene array locus control region (LCR) results in disruption of the cone mosaic. Vision Res 50:1989-99

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