The retinal pigment epithelium (RPE) plays a critical role in the maintenance of normal photoreceptor functions and has been implicated in several visual disorders, including macular degenerations and dystrophies. The investigator has cloned and characterized the first known RPE-specific human gene, RPE65, and has shown that mutations in this gene are responsible for certain forms of autosomal recessive childhood-onset severe retinal dystrophy (arCSRD), a finding supported by reports of RPE65 defects in Leber's congenital amaurosis. A research program has been developed to study the function of RPE65 in the normal biology of the retina and in the disease state, based on the view that RPE65 is necessary for the isomerase activity involved in the conversion of vitamin A to 11-cis retinal.
Four specific aims have been identified for the proposed funding period. (1) Recombinant protein-protein interactions and enzyme activity will be studied in cultured cells transfected with RPE65 expression constructs in order to distinguish between the two prevailing hypotheses about the specific role of RPE65 in RPE retinoid metabolism. (2) Site-directed mutagenesis will be used with assays of expression and protein function to elucidate the role of RPE65 mutations in the pathogenesis of arCSRD to test the hypothesis that disease-associated mutations in RPE65 result in functional null alleles that disrupt the 11-cis retinal biosynthetic pathway.
This aim will include further characterization of mutations present in patient populations. (3) Because preliminary information indicates that RPE65 is down-regulated by a variety of factors that are known to be related to aging and disease processes, and because decreased levels of RPE65 are implicated in retinal degeneration, the mechanisms involved in this down-regulation will be investigated, as well as the effects of aging and other physiological conditions on RPE65 expression. (4) Effects of the RPE65 mutation in a large animal model of arCSRD will be characterized in assays of the biochemistry and enzymology of retinoid metabolism, to test the hypothesis that defects resulting from RPE65 mutations will be amenable to retinal replacement therapy. The long-term goals of this project are to elucidate the mechanisms by which RPE65 defects contribute to retinal degeneration, and to lay the groundwork for the development of therapeutic approaches to the disease.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY012298-04
Application #
6653879
Study Section
Visual Sciences C Study Section (VISC)
Program Officer
Dudley, Peter A
Project Start
2000-09-30
Project End
2005-08-31
Budget Start
2003-09-01
Budget End
2004-08-31
Support Year
4
Fiscal Year
2003
Total Cost
$363,268
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Feathers, Kecia L; Lyubarsky, Arkady L; Khan, Naheed W et al. (2008) Nrl-knockout mice deficient in Rpe65 fail to synthesize 11-cis retinal and cone outer segments. Invest Ophthalmol Vis Sci 49:1126-35
Kurth, Ingo; Thompson, Debra A; Ruther, Klaus et al. (2007) Targeted disruption of the murine retinal dehydrogenase gene Rdh12 does not limit visual cycle function. Mol Cell Biol 27:1370-9
Thompson, Debra A; Janecke, Andreas R; Lange, Jessica et al. (2005) Retinal degeneration associated with RDH12 mutations results from decreased 11-cis retinal synthesis due to disruption of the visual cycle. Hum Mol Genet 14:3865-75
Hemati, Nahid; Feathers, Kecia L; Chrispell, Jared D et al. (2005) RPE65 surface epitopes, protein interactions, and expression in rod- and cone-dominant species. Mol Vis 11:1151-65
McHenry, Christina L; Liu, Yuhui; Feng, Wei et al. (2004) MERTK arginine-844-cysteine in a patient with severe rod-cone dystrophy: loss of mutant protein function in transfected cells. Invest Ophthalmol Vis Sci 45:1456-63
Felius, Joost; Thompson, Debra A; Khan, Naheed W et al. (2002) Clinical course and visual function in a family with mutations in the RPE65 gene. Arch Ophthalmol 120:55-61
Thompson, Debra A; McHenry, Christina L; Li, Yun et al. (2002) Retinal dystrophy due to paternal isodisomy for chromosome 1 or chromosome 2, with homoallelism for mutations in RPE65 or MERTK, respectively. Am J Hum Genet 70:224-9
Sieving, P A; Chaudhry, P; Kondo, M et al. (2001) Inhibition of the visual cycle in vivo by 13-cis retinoic acid protects from light damage and provides a mechanism for night blindness in isotretinoin therapy. Proc Natl Acad Sci U S A 98:1835-40
Thompson, D A; Li, Y; McHenry, C L et al. (2001) Mutations in the gene encoding lecithin retinol acyltransferase are associated with early-onset severe retinal dystrophy. Nat Genet 28:123-4