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theses

Kisspeptin (encoded by Kiss1), a neuropeptide critically involved in neuroendocrine regulation of reproduction, is primarily synthesized in two discrete hypothalamic nuclei: the anteroventral periventricular nucleus (AVPV) and arcuate nucleus (ARC). Current data indicates that AVPV Kiss1 is important for the pre-ovulatory luteinizing hormone (LH) surge unique to females as well as estrogen-induced positive feedback control of GnRH and LH. In contrast, ARC Kiss1 neurons, which largely co-express the neuropeptides NKB and dynorphin (collectively known as KNDy neurons), are thought to be the major regulators of pulsatile release of GnRH and LH, and mediate estrogen- induced negative feedback control of both GnRH and LH. Previous studies have not definitively separated the specific roles of Kiss1 in the AVPV versus KNDy-ARC neurons in the downstream control of GnRH and LH release. Therefore, we generated a Pdyn-Cre/Kiss1fl/fl (KO) mouse model to target Kiss1 in KNDy neurons to differentiate KNDy neuron-specific function from AVPV Kiss1 function in the maturation and maintenance of the reproductive axis. qRT-PCR data documented the loss of Kiss1 expression in the mediobasal hypothalamus (containing ARC) compared to controls, whereas Kiss1 in the preoptic area (containing AVPV) was similar in both KO and controls. Immunofluorescent staining for kisspeptin confirmed the loss of Kiss1 specifically in the ARC of KO mice. Although no changes in pubertal body weight gain or pubertal onset were observed in KO animals, KO females exhibited disrupted estrous cyclicity in adulthood. Interestingly, KO female mice had disrupted estrous cycles presenting with persistent diestrus and a small vaginal opening. We tested the hypothesis that ARC KNDy neurons are necessary for generating and maintaining episodic LH pulsatile release by serial collection of whole blood and measuring LH. KO female mice exhibited significantly fewer LH pulses in a 3-hour timespan compared to controls, suggesting that KNDy neurons were functionally compromised. These observations indicate the central role of KNDy neurons in the regulation of GnRH/LH pulsatility and estrous cyclicity. The functional effects of disrupted estrous cyclicity and slowed LH pulsatility observed in KO females result in arrested folliculogenesis and infertility. Future experiments will determine whether ARC Kiss1 deletion disrupts the KNDy- driven negative feedback response of LH to gonadectomy, as well as address potential sex differences in ARC Kiss1-mediated negative feedback control of LH release.

ETD_10817

M.S.

Includes bibliographical references

doi:10.7282/t3-93vj-8588

ETD graduate

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