Abstract
Pituitary gonadotropins play a pivotal role in reproduction. Long noncoding RNAs (lncRNAs) have been identified as important regulators in the hypothalamic–pituitary–ovarian (HPO) axis associated with reproduction. However, the contributions of lncRNAs to pituitary gonadotropin secretion remain largely unknown. Therefore, this work was performed to uncover the functional mechanisms of the novel lncRNA TCONS_00083279 (lncRNA SM2) and its potential targeting pathway oar-miR-16b/TGF-beta/SMAD2, which is associated with gonadotropin secretion in sheep pituitary cells. In the present study, the lncRNA SM2 showed high expression levels in the sheep pituitary gland, and it was located in both the nucleus and the cytoplasm of pituitary cells. lncRNA SM2 knockdown inhibited pituitary cell proliferation and FSH and LH secretion. The function of the lncRNA SM2 was sponged by oar-miR-16b, and this regulated the growth and gonadotropin secretion of pituitary cells by modulating SMAD2, as shown by the dual-luciferase reporter assay. FSH and LH levels were both upregulated by SMAD2 overexpression. Moreover, the levels of the lncRNA SM2, SMAD2 and TGFR1, as well as FSH and LH, in sheep pituitary cells increased significantly under gonadotropin-releasing hormone (GnRH) stimulation (p < 0.05). This work illustrates that the lncRNA SM2 regulates gonadotropin secretion in the Hu sheep anterior pituitary by targeting the oar-miR-16b/TGF-β/SMAD2 signaling pathway, providing a valuable resource for understanding the molecular mechanisms underlying sheep reproduction.
Highlights
The pituitary is composed of the neurohypophysis and the adenohypophysis in mammals, the latter of which constitutes the functional link between the nervous system and endocrine system [1]
The results show that oar-miR-16b could bind to the Long noncoding RNAs (lncRNAs) SM2 and SMAD2 3 -untranslated region (Figure 4A), suggesting that the lncRNA SM2 could act as a competing endogenous RNAs (ceRNAs) for oar-miR-16b to mediate SMAD2 expression in pituitary cells
In addition to well-characterized lncRNAs, it is worth exploring potential essential lncRNAs that control the mechanisms of gonadotropin secretion
Summary
The pituitary is composed of the neurohypophysis and the adenohypophysis in mammals, the latter of which constitutes the functional link between the nervous system and endocrine system [1]. Studies have shown that SMAD3 regulates the FSH secretion of pituitary gonadotropin cells [31]. We identified a differential candidate lncRNA (lncRNA SM2) and its targeted gene SMAD2 in Hu sheep pituitary glands with high and low prolificacy. We hypothesized that the lncRNA SM2 could act as a ceRNA to regulate gonadotropin secretion via the TGFβ/SMAD2 signaling pathway in Hu sheep pituitary cells. We identified the cytoplasmic localization of the lncRNA SM2 in Hu sheep pituitary cells and demonstrate that the lncRNA SM2 acted as a ceRNA to regulate gonadotropin secretion in pituitary cells via the TGF-β/SMAD2 pathway by acting as a molecular sponge to oar-miR-16b. This study focused on the regulatory mechanism between the lncRNA SM2 and the TGF-β/SMAD2 signaling pathway, thereby identifying a novel molecular pathway of FSH and LH secretion in pituitary cells
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