FRI283 Fragile X Gene Mutations Alter GnRH Neuron And Ovarian Innervation With Consequences On Reproductive Function

Disclosure: P.A. Villa: None. N. Lainez: None. C.R. Jonak: None. S. Berlin: None. I. Ethell: None. D. Coss: None. Mutations in the Fragile X messenger ribonucleoprotein 1 gene (FMR1) cause Fragile X syndrome, the most common cause of inherited mental disability, attributed to the loss of the Fragile X messenger ribonucleoprotein (FMRP). FMR1 mutations also comprise a majority of the genetic causes of premature ovarian failure (POF) in women, mechanisms of which are unknown. We utilized the Fmr1KO mouse model to determine the role of the FMR1 gene in the reproductive system in females. Similarly to what occurs in women harboring the mutation, our data demonstrate that Fmr1KO female mice experienced premature reproductive senescence, where reproductive function stopped at p163; in contrast, wild type controls stopped reproducing at p263. Since POF in women can occur due to either an insufficient pool of primordial follicles or early depletion of follicles, we quantified primordial follicles in 3 week old females and determined there was no difference between KO and controls. We then determined that Fmr1KO females had a higher number of corpora lutea at 8 weeks of age and gave birth to larger litters, suggesting that KO females recruit more follicles in each estrus cycle. Given that follicle stimulating hormone (FSH) and luteinizing hormone (LH) are essential in ovarian function, we analyzed gonadotropin levels in Fmr1KO females and determined they have higher serum LH and FSH. Inhibin b, progesterone, and testosterone levels were also higher, suggesting that high gonadotropins do not result from the lack of feedback. Ovariectomy determined that the hypothalamus drives high LH in KO females, while increased FSH is dependent on the ovaries. Increased vasculature in the corpora lutea and higher sympathetic innervation of developing follicles may increase steroid hormone production and drive increased serum FSH levels. To investigate the hypothalamic role in increased LH, we determined that a majority of gonadotropin-releasing hormone (GnRH) neurons express FMRP, which also have a higher number of GABAergic synapses in Fmr1KO females. Given that GABA is excitatory to GnRH neurons, alterations in afferent synaptic input can affect GnRH and LH secretion. LH pulsatile analysis determined higher LH pulse frequency in both unmodified and ovariectomized females, indicating an increase in GnRH neuron activity. In summary, our results reveal hypothalamic and ovarian contributions to the reproductive phenotype of Fragile X mutation carriers that may lead to early menopause. Presentation: Friday, June 16, 2023