SUN-243 Deletion of KNDy Neuron-Specific KISS1 Disrupts Estrous Cyclicity and LH Pulsatility in Female Mice

Abstract

Kisspeptin (encoded by Kiss1), a neuropeptide critically involved in neuroendocrine regulation of reproduction, is primarily synthesized in two discrete hypothalamic nuclei: the anteroventral periventricular area (AVPV) and arcuate nucleus (ARC). 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 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 fully separated the specific roles for 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 the 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 a significant reduction 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 IHC confirmed a loss of kisspeptin immunoreactivity in the ARC of KO animals while expression in the AVPV remained intact. Markers of pubertal onset (day of vaginal opening and first estrus in females; day of preputial separation in males) were normal in KO mice, suggesting that AVPV Kiss1 and/or other neural signals may be sufficient for pubertal onset. In addition, body weight throughout pubertal growth was comparable between KO and control animals of both sexes. Interestingly, KO female mice had disrupted estrous cycles presenting with persistent diestrus and a small vaginal opening. In order to test our hypothesis that conditional deletion of Kiss1 in KNDy neurons disrupts or ablates episodic GnRH/LH pulsatile release, we collected serial tail blood samples from mice at diestrus and measured 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 slower LH pulses observed in KO females are currently under study to assess potential abnormalities in ovarian folliculogenesis and fertility. 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.