Smad4 Feedback Enhances BMPR1B Transcription in Ovine Granulosa Cells

Abstract

BMPR1B is a type 1B receptor of the canonical bone morphogenetic protein (BMP)/Sma- and mad-related protein (Smad) signaling pathway and is well known as the first major gene associated with sheep prolificacy. However, little is known about the transcriptional regulation of the ovine BMPR1B gene. In this study, we identified the ovine BMPR1B gene promoter and demonstrated that its transcription was regulated by Smad4. In sheep ovarian follicles, three transcriptional variants of BMPR1B gene with distinct transcription start sites were identified using 5′ RACE assay while variants II and III were more strongly expressed. Luciferase assay showed that the region −405 to −200 nt is the PII promoter region of variant II. Interestingly, two putative Smad4-binding elements (SBEs) were detected in this region. Luciferase and ChIP assay revealed that Smad4 enhances PII promoter activity of the ovine BMPR1B gene by directly interacting with SBE1 motif. Furthermore, in the ovine granulosa cells, Smad4 regulated BMPRIB expression, and BMPRIB-mediated granulosa cells apoptosis. Overall, our findings not only characterized the 5’ regulatory region of the ovine BMPR1B gene, but also uncovered a feedback regulatory mechanism of the canonical BMP/Smad signaling pathway and provided an insight into the transcriptional regulation of BMPR1B gene and sheep prolificacy.

SMAD4 Feedback Activates the Canonical TGF-β Family Signaling Pathways

“…One of the highlights of this study is that we showed that SMAD4, the only Co-SMAD, has feedback activities to induce the expression of upstream receptors in GCs with a basal level of TGF-β ligands. As known, the ligands of TGF-β family signaling pathways, such as BMPs and TGF-βs, are secreted from GCs and further influence the activities of downstream signaling through both autocrine and paracrine methods [ 32 , 33 ]. Until now, few studies have reported the feedback activities of SMAD4 with exogenous ligands addition.…”

Ovarian transcriptomic analysis and follicular development of Leizhou black duck

“…Estrogen receptor 2 has been studied to play vital roles in the ovary during egg-laying stages and may be closely related to laying performance in ducks and may regulate key genes in granulosa cells essential for follicle maturation and ovulation ( Wu et al., 2014 ; Khristi et al., 2018 ). Bone morphogenetic protein receptor beta is a member of the TGF-β superfamily which is firstly expressed in primordial follicles on the oocyte and granulosa cells of primary follicles throughout folliculogenesis ( Regan et al., 2018a ; Abdurahman et al., 2019 ; Zhang et al., 2019 ).…”

The expression and mutation of <i>BMPR1B</i> and its association with litter size in small-tail Han sheep (<i>Ovis aries</i>)

“…BMPR1B (FecB) is one of the major fecundity genes in female reproduction and plays a major role in the development of follicles and the proliferation of ovarian granulosa cells in sheep (Shimasaki et al, 1999;Chu et al, 2007;Yao et al, 2019;Tao et al, 2019;Abdurahman et al, 2019). Previous reports have found that BMPR1B belongs to the type I receptors of BMPs (Aquino et al, 2017), which figure prominently in the proliferation of primordial germ cells (PGCs) (Nermin et al, 2018;Yi et al, 2001) and in the production and secretion of reproductive hormone (Richards and Pangas, 2010;Isaacs et al, 1995) by binding specifically to different types of ligands (Ikeda et al, 2016).…”