Leber congenital amaurosis (LCA) is a group of inherited retinal degenerative diseases characterized by nystagmus and blindness that typically manifest in the first year of life. As with several retinal degenerative diseases, many forms of LCA involve dysfunction of photoreceptor cilia. Mutations in the CEP290 gene are the most common cause of LCA, implicating CEP290 as a major contributor to the disease. CEP290 encodes a large protein proposed to regulate protein transport through the photoreceptor connecting cilium spanning the inner and outer segments. Using a mouse model of CEP290-mediated LCA, the rd16 mouse, we have found that the relative severity of Cep290 phenotypes in mice is highly sensitive to genetic background. Here, we propose experiments using mice that take advantage of this background sensitivity to identify genetic modifiers of Cep290-mediated retinal degeneration. Identification of these modifiers has both basic, and clinical, significance. From a basic biology perspective, studies of genetic modifiers can uncover basic biological functions of CEP290, photoreceptor cilia, and their gestalt contributions to retinal disease in a physiologic context. From a clinical perspective, identification of genetic modifiers offers an opportunity to identify therapeutic surrogates. The premise for our current proposal, its feasibility, and evidence of our ability to conduct quantitative modifier studies of retinal degeneration all stem from a relatively large body of recent work. We have performed large genetic crosses with mice and identified quantitative trait loci modifying retinal disease severity of mice homozygous for the Cep290rd16 mutation. Among regions of the genome identified as particularly important, our current proposal focuses on the Modifier of retinal degeneration quantitative trait locus 1 (Mrdq1) located on mouse chromosome 12. A unique feature of this modifier that has aided our ability to identify its molecular basis is that it shows imprinting?its influence varies according to parent-of-origin. Using physical mapping in combination with a study of retinal expressed genes that are imprinted, we have identified an overt mutation within a previously unstudied microRNA that is highly likely to be the causative mutation. Experiments of this proposal describe the work to stringently confirm that we have identified the precise mutation underlying the Mrdq1 modifier (Specific Aim 1), and begin to study its mechanisms of action through identification of downstream targets of the microRNA present in photoreceptors. At completion, we expect this work to have impact on CEP290-mediated LCA, as well as promote a better understanding of how two understudied phenomena, gene regulation via microRNAs and imprinting, influence retinal disease.

Public Health Relevance

Leber congenital amaurosis (LCA) is a group of inherited retinal degenerative blindness characterized by death of the light sensing photoreceptor cells of the outer retina. While some forms of LCA are treatable by gene therapy, the most common form, which is caused by mutations in the CEP290 gene, is currently untreatable. The objective in this proposal is to study features of CEP290-mediated biology that are currently hurdles to our basic scientific understanding of how this gene contributes to disease and how we might develop new strategies for treating CEP290-mediated LCA.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21EY029609-01
Application #
9616583
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Shen, Grace L
Project Start
2018-09-01
Project End
2020-08-31
Budget Start
2018-09-01
Budget End
2019-08-31
Support Year
1
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Iowa
Department
Physiology
Type
Schools of Medicine
DUNS #
062761671
City
Iowa City
State
IA
Country
United States
Zip Code
52242