Biphasic Roles of Clock Genes and Bone Morphogenetic Proteins in Gonadotropin Expression by Mouse Gonadotrope Cells

A novel lncRNA LOC105613571 binding with BDNF in pituitary promotes gonadotropin secretion by AKT/ERK-mTOR pathway in sheep associated with prolificacy

The pituitary is a vital endocrine organ for synthesis and secretion of gonadotropic hormones (FSH and LH), and the gonadotropin showed fluctuations in animals with different fecundity. Long non-coding RNAs (lncRNAs) have been identified as regulatory factors for the reproductive process. However, the profiles of lncRNAs and their roles involved in sheep fecundity remains unclear. In this study, we performed RNA-sequencing for the sheep pituitary gland associated with different fecundity, and identified a novel candidate lncRNA LOC105613571 targeting BDNF related to gonadotropin secretion. Our results showed that expression of lncRNA LOC105613571 and BDNF could be significantly upregulated by GnRH stimulation in sheep pituitary cells in vitro. Notably, either lncRNA LOC105613571 or BDNF silencing inhibited cell proliferation while promoted cell apoptosis. Moreover, lncRNA LOC105613571 knockdown could also downregulate gonadotropin secretion via inactivation AKT, ERK and mTOR pathway. In addition, co-treatment with GnRH stimulation and lncRNA LOC105613571 or BDNF knockdown showed the opposite effect on sheep pituitary cells in vitro. In summary, BDNF-binding lncRNA LOC105613571 in sheep regulates pituitary cell proliferation and gonadotropin secretion via the AKT/ERK-mTOR pathway, providing new ideas for the molecular mechanisms of pituitary functions.

Mutual Effects of Orexin and Bone Morphogenetic Proteins on Gonadotropin Expression by Mouse Gonadotrope Cells

Orexin plays a key role in the regulation of sleep and wakefulness and in feeding behavior in the central nervous system, but its receptors are expressed in various peripheral tissues including endocrine tissues. In the present study, we elucidated the effects of orexin on pituitary gonadotropin regulation by focusing on the functional involvement of bone morphogenetic proteins (BMPs) and clock genes using mouse gonadotrope LβT2 cells that express orexin type 1 (OX1R) and type 2 (OX2R) receptors. Treatments with orexin A enhanced LHβ and FSHβ mRNA expression in a dose-dependent manner in the absence of GnRH, whereas orexin A in turn suppressed GnRH-induced gonadotropin expression in LβT2 cells. Orexin A downregulated GnRH receptor expression, while GnRH enhanced OX1R and OX2R mRNA expression. Treatments with orexin A as well as GnRH increased the mRNA levels of Bmal1 and Clock, which are oscillational regulators for gonadotropin expression. Of note, treatments with BMP-6 and -15 enhanced OX1R and OX2R mRNA expression with upregulation of clock gene expression. On the other hand, orexin A enhanced BMP receptor signaling of Smad1/5/9 phosphorylation through upregulation of ALK-2/BMPRII among the BMP receptors expressed in LβT2 cells. Collectively, the results indicate that orexin regulates gonadotropin expression via clock gene expression by mutually interacting with GnRH action and the pituitary BMP system in gonadotrope cells.