Ovulation is triggered by a surge in luteinizing hormone (LH) secretion from the pituitary. The LH surge is itself driven by a surge in GnRH release induced by estrogen positive feedback action in the hypothalamus. While ERα-expressing kisspeptin (Kiss1) neurons in the preoptic area (in mice, the rostral periventricular region of the third ventricle RP3V) are proposed to mediate this estrogen positive feedback event, the functional necessity of RP3V-derived kisspeptin for the LH surge has not been directly tested. Here we leveraged Cre/lox technology and the known high co-expression of tyrosine hydroxylase (TH) with Kiss1 in only the RP3V region to generate novel transgenic mice with selective knockout (KO) of the Kiss1 gene in just RP3V neurons (Kiss1RP3V KO mice). In situ hybridization confirmed a significant 70% reduction in cells expressing Kiss1 in the RP3V region, but not in the arcuate nucleus, along with no change in RP3V Th expression. Kiss1RP3V KO females exhibited normal pubertal timing and estrous cycles. However, functional interrogation of the ability of Kiss1RP3V KO females to generate an estradiol-induced LH surge demonstrated markedly blunted LH surges and reduced occurrence of surges, in line with the partial Kiss1RP3V knockout in this group. Correspondingly, fertility assessment revealed significant subfertility, including fewer and smaller litters. This subfertility is consistent with the observed impaired LH surges, though the downstream ovarian mechanism(s) underlying the smaller litters still needs to be determined. These findings provide direct causal evidence that RP3V-derived kisspeptin is essential for normal LH surge magnitude and optimal fertility.
Puffer et al. (Thu,) studied this question.