Mechanisms of FMR1 gene-mediated reproductive disorders - ABSTRACT The overarching goal of this proposal is to elucidate the function of the fragile X messenger ribonucleoprotein 1 gene, FMR1, in the ovaries and its role in the regulation of reproductive function. Mutations of the FMR1 gene cause Fragile X syndrome, the most prevalent inherited cause of intellectual disability and the most common monogenic cause of autism spectrum disorder. Mutations of this gene also comprise the largest contribution of genetic causes of premature ovarian failure. The FMR1 gene has X-linked dominant inheritance, mutations have a high prevalence in the general population, and disorders have high penetrance in affected people. Although the molecular function of this gene’s product, FMRP, is beginning to emerge, mechanisms of related disorders are unknown. Our proposal is supported by ample evidence showing that mouse models mimic findings in human populations, prompting us to delve into molecular mechanisms. Specifically, Fmr1 knockout mice that lack Fmrp, mimicking people with these mutations, also experience reproductive disorders, such as premature cessation of reproductive function in females. Our previous publication revealed normal numbers of primordial follicles, demonstrating that in females, Fmr1 mutation does not affect the follicle pool, consistent with findings in humans. However, this mutation resulted in increased numbers of corpora lutea consistent with larger litters in young animals. In the ovary, Fmrp is expressed in the oocyte, granulosa cells, and in neuronal fibers that innervate the ovary. Young knockout females exhibit changes in hormone levels, including increased LH, FSH, inhibin B, and progesterone, as well as increased sympathetic innervation of the follicles by neuronal fibers that originate from the superior ovarian nerve. Our overarching hypothesis is that Fmr1 mutations alter ovarian responsiveness to hormonal stimulation and dysregulate follicle activation in young animals leading to early cessation of reproductive function. The first aim will determine whether the mutation causes the oocyte and granulosa cells to have different responsiveness to hormonal stimulation. This will be tested at different ages to pinpoint the affected cell type and timing of dysregulation. The second aim will investigate changes in the matrix surrounding the follicles that have been associated with ovarian aging. These exploratory aims fit the criteria for the R21 funding mechanism that will break new ground to identify the ovarian component primarily affected by the mutations and open new avenues of investigation. The third aim will use state-of-the-art virally induced neuronal activation to investigate the consequences of increased innervation on follicle activation. The role of ovarian sympathetic innervation arising from the superior ovarian nerve is not clear, and the high risk third aim may lead to novel understanding of the role innervation plays in hormone secretion or follicle development. This application will advance our knowledge of FMR1’s role in ovarian function, separately in the endocrine, stromal, and neuronal components. The findings will provide an understanding of reproductive disorders stemming from mutations in the Fragile X locus.
