In addition analysis of the functional elements in

In addition, analysis of the functional elements in the GnRH promoter region also identified other transcription factor binding sites, such as those for GATA-1 and Oct-1. However, those sites were not further validated in this study. Nevertheless, it has been reported that transcription factors such as GATA-1 and Oct-1 could bind to the GnRH promoter region, regulating GnRH expression (Clark and Mellon, 1995; Lawson et al., 1998). These results suggest that the promoter of the sheep GnRH gene may be bound by multiple transcription factors, as in humans and mice, but the specific transcriptional regulation mechanism requires further study.
Conclusion In conclusion, the kisspeptin-responsive core promoter of sheep GnRH was located at −1912 bp to −1461 bp, and a binding site for the transcription factor Otx-2 (−1786 bp to −1770 bp) was identified in the core promoter region. Furthermore, the LED209 was highly conserved among different species. Otx-2 and GnRH expression patterns were detected in the pituitary and hypothalamus of sheep, and the Otx-2 and GnRH expression patterns were the same in the hypothalamus during the breeding and nonbreeding seasons. After treatment with 1 nM kisspeptin, hypothalamic neurons cultured in vitro showed significantly upregulated expression of Otx-2 and GnRH. These data provide novel information on the sheep GnRH gene, namely, that the core promoter region from −1912 bp to −1461 bp is involved in kisspeptin-mediated hypothalamic activation and that binding of the transcription factor Otx-2 mediates this activation (Fig. 7).
Declaration of interest statement All authors of this manuscript declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, “Identification of a promoter element mediating kisspeptin-induced increases in GnRH gene expression in sheep”.
Author contributions
Acknowledgments This work was supported by the National Natural Science Foundation of China(Nos. 31501929 and 31702100), and the Research Fund for the Doctor Program of Higher Education of China (No. 20120204110007). The funders played no role in the study design, data collection and analysis, the decision to publish, or in the preparation of the manuscript.
Introduction The hormonal network responsible for reproductive function is under the control of the hypothalamic-pituitary-gonadal (HPG) axis, and gonadotropin-releasing hormone (GnRH) released from the hypothalamus is known to be at the pinnacle of this system. GnRH released from the hypothalamus stimulates the synthesis and release of the gonadotropins luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary. Gonadotropins released in response to GnRH pulses during the reproductive cycle act individually or cooperatively on the gonads to regulate steroidogenesis and gametogenesis. Briefly, FSH stimulates the growth and maturation of ovarian follicles in females and spermatogenesis in males. LH induces ovulation and formation of the corpus luteum in females and androgen secretion in males. Gonadal steroids, in turn, act to modulate the HPG axis to induce an LH surge (positive feedback) or to prevent excess steroid synthesis (negative feedback) (Gharib et al., 1990). After the first identification and isolation of GnRH (Matsuo et al., 1971, Schally et al., 1971), research into the neuroendocrine control of reproductive function by GnRH led to the development of agonists and antagonists of GnRH, resulting in advances in clinical applications for the treatment of hormonal disorders such as hormone-related cancer, endometriosis, uterine leiomyoma, precocious puberty, and infertility (Conn and Crowley, 1991). However, precisely how the secretion and expression of GnRH itself are regulated is still largely unknown.