Genetic Mechanisms Mediating Kisspeptin Regulation of GnRH gene Expression

Abstract

Kisspeptins (Kiss) have been shown to be key component in the regulation of gonadotropin-releasing hormone (GnRH) secretion. In vitro studies have demonstrated an increase in GnRH gene expression by Kiss suggesting regulation of GnRH at both the secretory and pretranslational levels. Here, we define genetic mechanisms that mediate Kiss action on target gene expression. In vitro, sequential deletions of the mGnRH gene promoter fused to the luciferase (LUC) reporter gene localized a kisspeptin-response element (KsRE) between −3446 bp and −2806 bp of the mGnRH gene. In vivo, transgenic mice bearing sequential deletions of the mGnRH gene promoter linked to the LUC reporter localized an identical KsRE. To define the mechanism of regulation, Kiss was first shown to induce nucleosome-depleted DNA within the KsRE, and a potential binding site for the transcription factor, Otx-2 was revealed. Furthermore, increased Otx-2 mRNA, protein and binding to the KsRE after Kiss treatment was demonstrated. In conclusion, this work identified elements in GnRH-neuronal cell lines and in transgenic mice that mediate positive regulation of GnRH by Kiss. In addition, we show for the first time that Otx-2 is regulated by Kiss, and plays a role in mediating the transcriptional response of mGnRH gene.

Real-Time GnRH Gene Transcription in GnRH Promoter-Driven Luciferase-Expressing Transgenic Mice: Effect of Kisspeptin

“…Considering the potent stimulatory effect of kisspeptin on the electrical activity of GnRH neurons [19] and GnRH promoter activity [20,21], we hypothesized that kisspeptin may play a crucial direct role in regulating the GnRH pulse generator (presumably the origin of GnRH pulsatility), in the context of the hypothalamic neural network.…”

Kisspeptin Induces Dynamic Chromatin Modifications to Control GnRH Gene Expression

“…Recently emerging players stimulating GnRH synthesis and secretion are kisspeptin and its G-protein-coupled receptor 54 (GPR54/KISS1R) [3][4][5][6][7]. The profound importance of kisspeptin signaling on GnRH neurons is noted in individuals carrying inactivating or deletion mutations in either the KISS1 or KISS1R gene who display normosmic idiopathic hypogonadotrophic hypogonadism (nIHH), hypgonadotropic hypogonadism (HH), and infertility [4,[8][9][10].…”

“…In addition, studies on the role of kisspeptin in the GnRH neuron have largely focused on cellular secretion of GnRH [14][15][16], and interestingly, more recent studies have related GnRH gene expression to secretion in response to kisspeptin stimulation [7,17,18]. Furthermore, in this context, through our previous studies using mouse-derived immortalized GnRH-secreting neuronal cell lines (GT1-7 and GN11) and transgenic mouse models, we have investigated the role of kisspeptin in modulating GnRH transcription/translation activity [7].…”

“…Furthermore, in this context, through our previous studies using mouse-derived immortalized GnRH-secreting neuronal cell lines (GT1-7 and GN11) and transgenic mouse models, we have investigated the role of kisspeptin in modulating GnRH transcription/translation activity [7]. These studies provided in vitro and in vivo evidence that the region between −3446-and −2806-bp upstream of the transcription start sites (TSSs) of the mGnRH gene is involved in the regulation of hypothalamic GnRH expression by kisspeptin, hence referred to as the kisspeptin response element (KsRE) [7]. In addition, these studies also demonstrated the modifications of chromatin conformation and the key role of the transcription factor, orthodenticle homeobox 2 (OTX-2), in mediating the transcriptional response of the mouse GnRH gene to kisspeptin [7].…”

“…These studies provided in vitro and in vivo evidence that the region between −3446-and −2806-bp upstream of the transcription start sites (TSSs) of the mGnRH gene is involved in the regulation of hypothalamic GnRH expression by kisspeptin, hence referred to as the kisspeptin response element (KsRE) [7]. In addition, these studies also demonstrated the modifications of chromatin conformation and the key role of the transcription factor, orthodenticle homeobox 2 (OTX-2), in mediating the transcriptional response of the mouse GnRH gene to kisspeptin [7].…”