Differentially expressed lncRNA-m433s1 regulates FSH secretion by functioning as a miRNA sponge in male rat anterior pituitary cells†

Role of microRNAs in pituitary gonadotrope cells

The gonadotrope cells within the pituitary control vital processes of reproduction by producing follicle stimulating hormone (FSH) and luteinizing hormone (LH). Both external stimuli and internal regulatory factors contribute to the regulation of gonadotrope development and function. In recent years, growing evidences indicate that microRNAs (miRNAs), which regulate gene expression post-transcriptionally, play critical roles in multiple processes of gonadotrope development and function, including the syntheses of α or β subunits of FSH and LH, the secretion of LH, the regulation of GnRH signaling, and the maintenance of gonadotrope cell kinetics. Here, we review recent advances of miRNAs' expression, functions and mechanisms approached by using miRNA knockout mouse models, in silico analysis and the in vitro cultures of primary pituitary cells and gonadotrope-derived cell lines. By summarizing and discussing different roles of miRNAs in gonadotropes, this minireview helps to gain insights into the complex molecular network in gonadotropes and reproduction.

GnRH-driven FTO-mediated RNA m6A modification promotes gonadotropin synthesis and secretion

BACKGROUND

Gonadotropin precisely controls mammalian reproductive activities. Systematic analysis of the mechanisms by which epigenetic modifications regulate the synthesis and secretion of gonadotropin can be useful for more precise regulation of the animal reproductive process. Previous studies have identified many differential m6A modifications in the GnRH-treated adenohypophysis. However, the molecular mechanism by which m6A modification regulates gonadotropin synthesis and secretion remains unclear.

RESULTS

Herein, it was found that GnRH can promote gonadotropin synthesis and secretion by promoting the expression of FTO. Highly expressed FTO binds to Foxp2 mRNA in the nucleus, exerting a demethylation function and reducing m6A modification. After Foxp2 mRNA exits the nucleus, the lack of m6A modification prevents YTHDF3 from binding to it, resulting in increased stability and upregulation of Foxp2 mRNA expression, which activates the cAMP/PKA signaling pathway to promote gonadotropin synthesis and secretion.

CONCLUSIONS

Overall, the study reveals the molecular mechanism of GnRH regulating the gonadotropin synthesis and secretion through FTO-mediated m6A modification. The results of this study allow systematic interpretation of the regulatory mechanism of gonadotropin synthesis and secretion in the pituitary at the epigenetic level and provide a theoretical basis for the application of reproductive hormones in the regulation of animal artificial reproduction.

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.

Whole transcriptome analysis reveals the key genes and noncoding RNAs related to follicular atresia in broilers

Broodiness, a maternal behavior, is accompanied by the atresia of follicles and the serious degradation of poultry reproductive performance. The comparison of follicles between brooding and laying hens is usually an ideal model for exploring the regulation mechanism of follicle atresia. In this study, we selected three brooding hens and three laying hens to collect their follicles for whole transcriptome sequencing. The results demonstrated different expression patterns between the follicles of brooding hens and laying hens. In the top 10 differentially expressed genes with the highest expression, MMP10 was relatively low expressed in the follicles of brooding hens, but other nine genes were relatively highly expressed, including LRR1, RACK1, SPECC1L, ABHD2, COL6A3, RPS17, ATRN, BIRC6, PGAM1 and SPECC1L. While miR-21-3p, miR-146a-5p, miR-142-5p and miR-1b-3p were highly expressed in the follicles of brooding hen, miR-106-5p, miR-451, miR-183, miR-7, miR-2188-5p and miR-182-5p were lowly expressed in brooding hen. In addition, we identified 124 lncRNAs specifically expressed in the follicles of brooding hens and 147 lncRNAs specifically expressed in the follicles of laying hens. Our results may provide a theoretical basis for further exploration of the molecular mechanism of broodiness in broilers.

Interaction of lncRNA Gm2044 and EEF2 promotes estradiol synthesis in ovarian follicular granulosa cells

The functions and molecular mechanisms of long noncoding RNA (lncRNA) in reproduction have been widely studied at present. However, lncRNA regulating hormone synthesis in ovarian follicular granulosa cells has not been sufficiently studied. Our previous research demonstrated that lncRNA Gm2044 could promote estradiol synthesis in follicular granulosa cells. In this study, we identified 21 binding proteins of lncRNA Gm2044 in ovarian follicles using comprehensive identification of RNA-binding proteins by mass spectrometry (ChIRP-MS). RNA immunoprecipitation (RNA IP) and reverse transcription PCR (RT-PCR) confirmed that lncRNA Gm2044 can interact with eukaryotic translation elongation factor 2 (EEF2) protein. Furthermore, we constructed lncRNA Gm2044 knockout mice using the CRISPR/Cas9 method. Although the follicular development and fertility of female lncRNA Gm2044 knockout mice were not affected, the serum estradiol concentration in female lncRNA Gm2044 knockout mice significantly decreased. Western blotting and ELISA revealed that lncRNA Gm2044 may promote the binding of EEF2 to Nr5a1 mRNA and then enhance the Nr5a1 mRNA translation, and the upregulated NR5A1 protein can strengthen estradiol synthesis. To determine the potential signaling pathway of lncRNA Gm2044 regulating estradiol synthesis, transcriptome sequencing was performed for ovaries of adult lncRNA Gm2044 knockout mice, which identified 565 significant up-regulated genes and 303 significant down-regulated genes, which were then analyzed with Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) and validated by molecular experiments. Understanding how lncRNA Gm2044/EEF2 protein regulates estradiol synthesis will help treat estrogen-related reproductive diseases.

EZH2 Gene Knockdown Inhibits Sheep Pituitary Cell Proliferation via Downregulating the AKT/ERK Signaling Pathway

Pituitary gonadotropins perform essential functions in mammalian reproduction by stimulating gametogenesis and steroidogenesis in the ovaries and testicles. EZH2 is a histone methyltransferase that inhibits proliferation and aggravates apoptosis in stem cells subjected to pathological stimuli. However, the expression and molecular mechanisms of EZH2 in pituitary cells in vitro have not been extensively studied. In this study, the relative abundances of EZH2 mRNA (p < 0.01) and protein (p < 0.05) expression were larger in the pituitary cells of Hu sheep with relatively greater fecundity (GF) compared to those with lesser fecundity (LF). Loss-of-function examinations demonstrated that EZH2 gene knockdown led to an earlier induction of apoptosis in sheep pituitary cells (PCs). The relative abundance of CASP3, CASP9, and BAX was increased (p < 0.01), while BCL2's abundance was less decreased (p < 0.01) in PCs where there was EZH2 gene knockdown. Additionally, cell proliferation (p < 0.01) and viability (p < 0.01) were decreased in EZH2-knockdown sheep PCs, and the cell cycle was blocked compared to a negative control (NC). Notably, EZH2 gene knockdown led to reduced abundances of gonadotropin subunit gene transcripts (FSHβ, p < 0.05) and reduced FSH release (p < 0.01) from PCs. EZH2 gene knockdown led to reduced phosphorylation of AKT, ERK, and mTOR (p < 0.01). The results suggest that EZH2 regulates pituitary cell proliferation, apoptosis, and FSH secretion through modulation of the AKT/ERK signaling pathway, providing a foundation for further study of pituitary cell functions.

Sequencing of the Pituitary Transcriptome after GnRH Treatment Uncovers the Involvement of lncRNA-m23b/miR-23b-3p/CAMK2D in FSH Synthesis and Secretion

The pituitary gland is a key participant in the hypothalamic–pituitary–gonadal axis, as it secretes a variety of hormones and plays an important role in mammalian reproduction. Gonadotrophin-releasing hormone(GnRH) signaling molecules can bind to GnRH receptors on the surfaces of adenohypophysis gonadotropin cells and regulate the expression of follicle-stimulating hormone(FSH) and luteinizing hormone(LH) through various pathways. An increasing number of studies have shown that noncoding RNAs mediate the regulation of GnRH signaling molecules in the adenohypophysis. However, the expression changes and underlying mechanisms of genes and noncoding RNAs in the adenohypophysis under the action of GnRH remain unclear. In the present study, we performed RNA sequencing (RNA-seq) of the rat adenohypophysis before and after GnRH treatment to identify differentially expressed mRNAs, lncRNAs, and miRNAs. We found 385 mRNAs, 704 lncRNAs, and 20 miRNAs that were significantly differentially expressed in the rat adenohypophysis. Then, we used a software to predict the regulatory roles of lncRNAs as molecular sponges that compete with mRNAs to bind miRNAs, and construct a GnRH-mediated ceRNA regulatory network. Finally, we enriched the differentially expressed mRNAs, lncRNA target genes, and ceRNA regulatory networks to analyze their potential roles. Based on the sequencing results, we verified that GnRH could affect FSH synthesis and secretion by promoting the competitive binding of lncRNA-m23b to miR-23b-3p to regulate the expression of Calcium/Calmodulin Dependent Protein Kinase II Delta(CAMK2D). Our findings provide strong data to support exploration of the physiological processes in the rat adenohypophysis under the action of GnRH. Furthermore, our profile of lncRNA expression in the rat adenohypophysis provides a theoretical basis for research on the roles of lncRNAs in the adenohypophysis.

The Novel Competing Endogenous Long Noncoding RNA SM2 Regulates Gonadotropin Secretion in the Hu Sheep Anterior Pituitary by Targeting the Oar-miR-16b/TGF-β/SMAD2 Signaling Pathway

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.

Enhancing Gonadotrope Gene Expression Through Regulatory lncRNAs

The world of long non-coding RNAs (lncRNAs) has opened up massive new prospects in understanding the regulation of gene expression. Not only are there seemingly almost infinite numbers of lncRNAs in the mammalian cell, but they have highly diverse mechanisms of action. In the nucleus, some are chromatin-associated, transcribed from transcriptional enhancers (eRNAs) and/or direct changes in the epigenetic landscape with profound effects on gene expression. The pituitary gonadotrope is responsible for activation of reproduction through production and secretion of appropriate levels of the gonadotropic hormones. As such, it exemplifies a cell whose function is defined through changes in developmental and temporal patterns of gene expression, including those that are hormonally induced. Roles for diverse distal regulatory elements and eRNAs in gonadotrope biology have only just begun to emerge. Here, we will present an overview of the different kinds of lncRNAs that alter gene expression, and what is known about their roles in regulating some of the key gonadotrope genes. We will also review various screens that have detected differentially expressed pituitary lncRNAs associated with changes in reproductive state and those whose expression is found to play a role in gonadotrope-derived nonfunctioning pituitary adenomas. We hope to shed light on this exciting new field, emphasize the open questions, and encourage research to illuminate the roles of lncRNAs in various endocrine systems.

Advances in the Regulation of Mammalian Follicle-Stimulating Hormone Secretion

Simple Summary

The reproduction of mammals is regulated by the hypothalamic-pituitary-gonadal axis. Follicle stimulating hormone, as one of the gonadotropins secreted by the pituitary gland, plays an immeasurable role. This article mainly reviews the molecular basis and classical signaling pathways that regulate the synthesis and secretion of follicle stimulating hormone, and summarizes its internal molecular mechanism, which provides a certain theoretical basis for the research of mammalian reproduction regulation and the application of follicle stimulating hormone in production practice.

Abstract

Mammalian reproduction is mainly driven and regulated by the hypothalamic-pituitary-gonadal (HPG) axis. Follicle-stimulating hormone (FSH), which is synthesized and secreted by the anterior pituitary gland, is a key regulator that ultimately affects animal fertility. As a dimeric glycoprotein hormone, the biological specificity of FSH is mainly determined by the β subunit. As research techniques are being continuously innovated, studies are exploring the underlying molecular mechanism regulating the secretion of mammalian FSH. This article will review the current knowledge on the molecular mechanisms and signaling pathways systematically regulating FSH synthesis and will present the latest hypothesis about the nuclear cross-talk among the various endocrine-induced pathways for transcriptional regulation of the FSH β subunit. This article will provide novel ideas and potential targets for the improved use of FSH in livestock breeding and therapeutic development.

LncRNA lnc_13814 promotes the cells apoptosis in granulosa cells of duck by acting as apla-miR-145-4 sponge

Follicle development is a vital factor which determines the reproductive performance of poultry. Long noncoding RNAs (lncRNAs) have been reported to maintain animal reproductive function and play key roles in ovarian development and hormone secretion. But the regulatory mechanism of lncRNAs in duck follicle development has seldom been reported. In this study, to better explore the molecular mechanism of follicle development in ducks, the follicular lncRNA was sequenced and analyzed. A total of 9,551 lncRNAs were predicted in the duck follicles. Four hundred and forty-five lncRNAs were differentially expressed between the white follicles and yellow follicles. The results of our studies showed that lnc_13814 promoted cell apoptosis in duck GCs. Furthermore, the bioinformatics analysis results demonstrated that lnc_13814 was involved in a lncRNA-miRNA-mRNA coexpression network and it was observed to sponge two follicle-related miRNAs by a luciferase activity assay. Moreover, we found that overexpression of lnc_13814 significantly increased DNA damage inducible transcript 3 (DDIT3) expression and downregulated GCs apoptosis. Finally, we found that lnc_13814 directly binds to and inhibits apla-mir-145-4; then, lnc_13814 increases the expression of DDIT3 and up-regulates GCs apoptosis. Taken together, our findings demonstrate that lncRNAs have potential effects on duck ovarian follicles and lncRNAs may represent a new approach to understand follicular development.

CircAgtpbp1 Acts as a Molecular Sponge of miR-543-5p to Regulate the Secretion of GH in Rat Pituitary Cells

CircRNAs have been identified to be expressed differently and stably in numerous species and tissues, but their functions in growth hormone (GH) secretion are still largely unknown. In summary, we have revealed a circRNA-miRNA-mRNA network that may play a biological role in the rat pituitary gland. First, we verified the chromosome location information of circAgtpbp1 according to sequencing analysis. The circAgtpbp1 characteristics were authenticated through PCR, qRT-PCR, treating with RNase and fluorescent in situ hybridization (FISH). Second, we detected the expression pattern of circAgtpbp1 in the rat anterior pituitary by qRT-PCR. We also designed circAgtpbp1 siRNA and constructed overexpression plasmid to evaluate the effect of circAgtpbp1 function on GH secretion by qRT-PCR, ELISA and Western blot. CircAgtpbp1 is a stable, truly circular molecule. We found that circAgtpbp1 interacted with miR-543-5p and can regulate GH secretion in pituitary cells through a circAgtpbp1-miR-543-5p-GH axis. Overall, the evidence generated by our study suggests that circAgtpbp1 can act as a sponge of miR-543-5p to reduce the inhibitory effect of miR-543-5p on Gh1 and further promote GH secretion. These findings expand our existing knowledge on the mechanisms of hormone regulation in the pituitary gland.

Insight Into Pituitary lncRNA and mRNA at Two Estrous Stages in Small Tail Han Sheep With Different FecB Genotypes

The pituitary is a remarkably dynamic organ with roles in hormone (FSH and LH) synthesis and secretion. In animals with the FecB (fecundity Booroola) mutation, the pituitary experiences hormone fluctuations during the follicular-luteal transition, which is implicated in the expression and regulation of many genes and regulators. Long non-coding RNAs (lncRNAs) are a novel type of regulatory factors for the reproductive process. Nevertheless, the expression patterns of lncRNAs and their roles in FecB-mediated follicular development and ovulation remain obscure. Thus, we profiled the pituitary transcriptome during the follicular (F, 45 h after evacuation vaginal sponges) and luteal (L, 216 h after evacuation vaginal sponges) phases in FecB-mutant homozygous (BB) and wild-type (WW) Small Tail Han sheep. We identified 78 differentially expressed genes (DEGs) and 41 differentially expressed lncRNAs (DELs) between BB_F and BB_L, 32 DEGs and 26 DELs between BB_F and WW_F, 16 DEGs and 29 DELs between BB_L and WW_L, and 50 DEGs and 18 DELs between WW_F and WW_L. The results of real-time quantitative PCR (RT-qPCR) correlated well with the transcriptome data. In both the follicular and luteal phases, DEGs (GRID2, glutamate ionotropic receptor delta type subunit 2; ST14, ST14 transmembrane serine protease matriptase) were enriched in hormone synthesis, secretion, and action. MSTRG.47470 and MSTRG.101530 were the trans-regulated elements of ID1 (inhibitor of DNA binding 3, HLH protein) and the DEG ID3 (inhibitor of DNA binding 3, HLH protein), and EEF2 (eukaryotic translation elongation factor 2), respectively; these factors might be involved in melatonin and peptide hormone secretion. In the FecB-mediated follicular phase, MSTRG.125392 targeted seizure-related 6 homolog like (SEZ6L), and MSTRG.125394 and MSTRG.83276 targeted the DEG KCNQ3 (potassium voltage-gated channel subfamily Q member 3) in cis, while MSTRG.55861 targeted FKBP4 (FKBP prolyl isomerase 4) in trans. In the FecB-mediated luteal phase, LOC105613905, MSTRG.81536, and MSTRG.150434 modulated TGFB1, SMAD3, OXT, respectively, in trans. We postulated that the FecB mutation in pituitary tissue elevated the expression of certain genes associated with pituitary development and hormone secretion. Furthermore, this study provides new insights into how the pituitary regulates follicular development and ovulation, illustrated by the effect of the FecB mutation.

Human Follicle-Stimulating Hormone ß Subunit Expression Depends on FOXL2 and SMAD4

Follicle-stimulating hormone (FSH), an essential regulator of mammalian fertility, is synthesized by pituitary gonadotrope cells in response to activins. In mice, activins signal via SMAD3, SMAD4, and FOXL2 to regulate transcription of the FSHβ subunit (Fshb) gene. Gonadotrope-specific deletion of Foxl2, alone or in combination with Smad4, renders mice FSH-deficient. Whether human FSHB expression is similarly regulated is not known. Here, we used a combination of transgenic and conditional knockout mouse strains to assess the roles of activins, FOXL2, and SMAD4 in regulation of the human FSHB gene. First, we cultured pituitaries from mice harboring a human FSHB transgene (hFSHB mice) and measured both murine Fshb and human FSHB messenger ribonucleic acid (mRNA) expression in response to exogenous activins or two antagonists of endogenous activin-like signaling (follistatin-288 and SB431542). Both murine Fshb and human FSHB expression were stimulated by activins and reduced by the inhibitors. Next, we analyzed human FSHB expression in hFSHB mice carrying floxed Foxl2 and Smad4 alleles. Cre-mediated ablation of FOXL2 and SMAD4 strongly reduced basal and activin-stimulated murine Fshb and human FSHB expression in cultured pituitaries. Finally, the hFSHB transgene was previously shown to rescue FSH production and fertility in Fshb knockout mice. However, gonadotrope-specific Foxl2/Smad4 knockout females carrying the hFSHB transgene have significantly reduced murine Fshb and human FSHB pituitary mRNA levels and are hypogonadal. Collectively, these data suggest that similar to Fshb regulation in mice, FOXL2 and SMAD4 play essential roles in human FSHB expression.

Genome-Wide Analysis and Function Prediction of Long Noncoding RNAs in Sheep Pituitary Gland Associated with Sexual Maturation

Long noncoding RNA (lncRNA) plays a crucial role in the hypothalamic-pituitary-testis (HPT) axis associated with sheep reproduction. The pituitary plays a connecting role in the HPT axis. However, little is known of their expression pattern and potential roles in the pituitary gland. To explore the potential lncRNAs that regulate the male sheep pituitary development and sexual maturation, we constructed immature and mature sheep pituitary cDNA libraries (three-month-old, TM, and nine-month-old, NM, respectively, n = 3) for lncRNA and mRNA high-throughput sequencing. Firstly, the expression of lncRNA and mRNA were comparatively analyzed. 2417 known lncRNAs and 1256 new lncRNAs were identified. Then, 193 differentially expressed (DE) lncRNAs and 1407 DE mRNAs were found in the pituitary between the two groups. Moreover, mRNA-lncRNA interaction network was constructed according to the target gene prediction of lncRNA and functional enrichment analysis. Five candidate lncRNAs and their targeted genes HSD17B12, DCBLD2, PDPK1, GPX3 and DLL1 that enriched in growth and reproduction related pathways were further filtered. Lastly, the interaction of candidate lncRNA TCONS_00066406 and its targeted gene HSD17B12 were validated in in vitro of sheep pituitary cells. Our study provided a systematic presentation of lncRNAs and mRNAs in male sheep pituitary, which revealed the potential role of lncRNA in male reproduction.