The goals of our Center, 'Modifiers of FMR1-associated disorders: application of high throughput technologies, are targeted to the RFA research area to Advance the understanding of the pathophysiology of FMR1 Related Conditions. The completion of the proposed aims from the three research projects will lead to the identification of the genetic basis of variable expressivity or incomplete penetrance of FMR1-associated conditions by searching for modifying loci by whole genome sequencing (WGS) of 200 subjects in each of the three projects. Project A will focus on the variable expression of epilepsy among boys with fragile X syndrome (FXS), a co-morbid condition that occurs among 15% of affected boys and we speculate that variation elsewhere in the genome is responsible. Likewise, Project B will focus on the incomplete penetrance of fragile X tremor/ataxia syndrome (FXTAS) in men, a neurodegenerative disorder among those with the premutation (PM), with a lifetime prevalence of 30% among males. Project C, the topic of this project proposal, focuses fragile X association primary ovarian insufficiency (FXPOl) which manifests in 20% of PM carriers as premature ovarian failure (POF), or cessation of menses prior to age 40. POF leads to infertility and estrogen-deficiency related disorders usually reserved for the aged. Other PM carriers have a normal reproductive life span. Our goal is to identify and understand the extent of the epistatic effects of modifying genes on these three Mendelian disorders. We will recruit FMR1 repeat mutation carriers from the tails of the phenotype distribution and compare their genetic variant profiles obtained from WGS. Specifically for this project, women who experience cessation of menses for at least four months prior to age 35 will be defined as case probands and women who experience menopause after age 50 and have no indication of infertility will be defined as control probands. Prioritized candidate genes from WGS will be validated and then functionally assessed using high throughput phenotype assays in Drosophila. This project will equally use shared Center cores: Recruitment Core B and the Genomics and Analytical Core C. We anticipate that identified modifying genes of FXPOl will provide insight into interventions for women ovarian insufficiency. We have established a collaboration with ReproGen Consortium, a group that has brought together genetic data on age at menopause from many well-defined cohorts, including data on greater than 50,000 women. They will be able to interrogate their meta-data to further determine the value of our identified variants for future studies.
The identification of genes whose variation modifies the phenotype of a Mendelian disorder is emerging at the forefront of contemporary human genetics. Characterizing those modifying genes for fragile X syndrome-associated epilepsy, fragile X-associated ovarian insufficiency and fragile X-associated tremor/ataxia syndrome will increase the understanding of perturbed pathways involved in these disorders.
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