The Role of Kisspeptin Signaling in Reproduction of Ruminants

In the present decade, kisspeptin has been a fascinating topic in the reproductive spotlight. Kisspeptin is a neuropeptide, produced mainly in the hypothalamus from Kiss1 gene. This gene was initially discovered in 1996 as a tumor suppressor gene in human malignant melanoma. Then in the year 2003, researchers found that mutations of the G protein-coupled receptor (GPR54), which is the strongly cognate receptor of kisspeptin, were associated with hypogonadotropic hypogonadism in mice and humans. There are many kisspeptin distribution and function studies (both in vitro and in vivo) in mammals. In ruminants, kisspeptin has been studied mainly in sheep and to some extent in goats and cattle. In ewes, Kiss1 is expressed in the arcuate nucleus to forward signals relevant to negative feedback regulation of gonadotropin releasing hormone (GnRH), and is also responsible for positive feedback regulation of GnRH at the time of the preovulatory GnRH/luteinizing hormone (LH) surge via the hypophyseal portal circulation. Although there are Kiss1 cells in the preoptic area, whether they play a role in the sex steroid feedback regulation of GnRH secretion has not been discovered yet. Previous research indicates, however, that kisspeptin-GPR54 signaling is a key regulator of puberty, reproductive function and fertility via the hypothalamic pituitary gonadal axis, which produces a neuroendocrine substrate to stimulate gonadotropin releasing hormone and has the potential to replay feedback effects from the sex hormones to GnRH neurons. [PUBLICATION ABSTRACT]