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As the key regulator of reproduction, gonadotropin-releasing hormone (GnRH) is released by neurons in the hypothalamus, and transported via the hypothalamo-hypophyseal portal circulation to the anterior pituitary to trigger gonadotropin release for gonadal steroidogenesis and gametogenesis. To achieve appropriate reproductive function, mammals have precise regulatory mechanisms; one of these is the control of GnRH synthesis and release. In the past, the scarcity of GnRH neurons and their widespread distribution in the brain hindered the study of GnRH gene expression. Until recently, the development of GnRH-expressing cell lines with properties similar to those of in vivo GnRH neurons and also transgenic mice facilitated GnRH gene regulation research. This minireview provides a summary of the molecular mechanisms for the control of GnRH-I and GnRH-II gene expression. These include basal transcription regulation, which involves essential cis-acting elements in the GnRH-I and GnRH-II promoters and interacting transcription factors, and also feedback control by gonadotropins and gonadal sex steroids. Other physiological stimuli, e.g. insulin and melatonin, will also be discussed. [ABSTRACT FROM AUTHOR]

Gonadotropin-releasing hormone (GnRH) I and II are hypothalamic decapeptides with pivotal roles in the development of reproductive competence and regulation of reproductive events. In this study, transcriptional regulation of the human GnRH II gene was investigated. By scanning mutation analysis coupled with transient promoter assays, the motif at −641/−636 (CATGCC, designated GII-Sil) was identified as a repressor element. Mutation of this motif led to full restoration of promoter activity in TE671 medulloblastoma and JEG-3 placenta choriocarcinoma cells. Supershift and chromatin immunoprecipitation assays showed in vitro and in vivo binding of NF-κB subunit p65 and the retinoic acid receptors, RARα and RXRα, to the promoter sequences. Over-expression of these protein factors indicated that p65 is a potent repressor, and the RARα/RXRα heterodimer is involved in the differential regulation of the GnRH II gene in neuronal and placental cells. This was confirmed by quantitative real-time PCR. Treatment of cells with the RARα/RXRα ligands, all- trans retinoic acid and 9- cis-retinoic acid, reduced and increased GnRH II gene expression in TE671 and JEG-3 cells, respectively. Taken together, these data demonstrate the differential roles of NF-κB p65 and RARα/RXRα, interacting with the same sequence in the promoter of the human GnRH II gene to influence gene expression in a cell-specific manner. [ABSTRACT FROM AUTHOR]

The article reports on the gonadotropin-releasing hormone (GnRH). According to the author, investigations toward the understanding of the role of GnRH in physiological functions, is needed. Furthermore, the author adds that GnRh is also relevan in tumor progresson, as shown by studies on specific cancers. Lastly, the author relates the connection between ovarian cancer and GnRH receptor.