GnRH Promotes Gonadotropin Synthesis and Secretion in the Bovine Anterior Pituitary by Inhibiting METTL1-Mediated m7G Modification of FOXO1 mRNA.

The pituitary gland is a key regulator of mammalian reproduction. By secreting the gonadotropins-follicle-stimulating hormone (FSH) and luteinizing hormone (LH)-the anterior pituitary precisely coordinates reproductive function. The hypothalamus releases gonadotropin-releasing hormone (GnRH), which in turn regulates the synthesis and secretion of gonadotropins by the anterior pituitary gland. Although GnRH-dependent regulation of pituitary gonadotropins has been extensively studied in rodents, the mechanisms by which GnRH regulates gonadotropins in the bovine anterior pituitary gland remain unclear. In this research, we primarily used primary bovine anterior pituitary cells (PCs) for the experiments, and employed the mouse gonadotropin cell line LβT2 to further validate the regulatory effect of GnRH on pituitary gonadotropin-secreting cells. We first demonstrated that GnRH promotes bovine gonadotropin synthesis and secretion and concomitantly reduces global cellular m7G methylation. Further experiments demonstrated that METTL1, a key methyltransferase responsible for m7G modification, is downregulated after GnRH treatment and functions as a negative regulator of gonadotropin synthesis and secretion. Mechanistically, experiments such as MeRIP-qPCR and RNA stability analyses showed that METTL1 mediates m7G methylation of bovine FOXO1 mRNA, thereby modulating FOXO1 stability and protein expression, and regulating gonadotropin synthesis and secretion. Collectively, these findings demonstrate that GnRH regulates gonadotropin synthesis and secretion in the bovine anterior pituitary, and reveal an important role for RNA epigenetic modification in this process.