Gain-of-Function Genetic Models to Study FSH Action

Dynamic Expression of Follicle-Stimulating Hormone and Estrogen mRNA Receptors Associated with microRNAs 34a and -let-7c in Canine Follicles during the Estrous Cycle

The genes encoding for estrogen receptor (ESR2) and follicle-stimulating hormone receptor (FSHR) play crucial roles in ovarian follicular development. This study aimed to determine the expression levels of miRNAs predicted against FSHR and ESR2 mRNAs in follicular cells related to their target genes during the estrous cycle in canines. Antral follicles were dissected from 72 ovaries following ovariohysterectomies. MiRNAs regulating FSHR and ESR2 genes were selected from miRNA databases, and mature miRNA and mRNA expression profiling was performed using real-time polymerase chain reaction (PCR). The best miRNA for each target gene was selected considering the quantitative PCR (qPCR) performance and target prediction probability, selecting only miRNAs with a binding p-value of 1.0, and choosing cfa-miR-34a and cfa-let-7c for FSHR and ESR2, respectively. The expression levels comparing the different phases of the estrous cycle were evaluated using ANOVA. Pearson correlations between the expression pattern of each miRNA and their target genes were performed. Each miRNA and its target genes were expressed in the granulosa cells in all estrous phases. FSHR remained low in anestrus and proestrus, increased (p < 0.05) to the highest level in estrus, and decreased (p < 0.05) in diestrus. ESR2 showed the same trend as FSHR, with the highest (p < 0.05) expression in estrus and the lowest (p < 0.05) in anestrus and proestrus. A tendency for an inverse relationship was observed between the expression of miR-34a and FSHR only in the anestrus phase, while an inverse correlation (r = -0.8) was found between miRNA-7c and ESR2 (p < 0.01). The expression profile of miR-34a and miR-let-7c and their predicted target genes of dog ovarian follicles throughout the estrous cycle observed in this study suggest a role in the transcriptional regulation of FSHR and ESR2, which is the first evidence of the involvement of these miRNAs in the canine follicular function.

Musashi Exerts Control of Gonadotrope Target mRNA Translation During the Mouse Estrous Cycle

The anterior pituitary controls key biological processes, including growth, metabolism, reproduction, and stress responses through distinct cell types that each secrete specific hormones. The anterior pituitary cells show a remarkable level of cell type plasticity that mediates the shifts in hormone-producing cell populations that are required to meet organismal needs. The molecular mechanisms underlying pituitary cell plasticity are not well understood. Recent work has implicated the pituitary stem cell populations and specifically, the mRNA binding proteins of the Musashi family in control of pituitary cell type identity. In this study we have identified the target mRNAs that mediate Musashi function in the adult mouse pituitary and demonstrate the requirement for Musashi function in vivo. Using Musashi RNA immunoprecipitation, we identify a cohort of 1184 mRNAs that show specific Musashi binding. Identified Musashi targets include the Gnrhr mRNA, which encodes the gonadotropin-releasing hormone receptor (GnRHR), and the Fshb mRNA, encoding follicle-stimulating hormone (FSH). Reporter assays reveal that Musashi functions to exert repression of translation of the Fshb mRNA, in addition to the previously observed repression of the Gnrhr mRNA. Importantly, mice engineered to lack Musashi in gonadotropes demonstrate a failure to repress translation of the endogenous Gnrhr and Fshb mRNAs during the estrous cycle and display a significant heterogeneity in litter sizes. The range of identified target mRNAs suggests that, in addition to these key gonadotrope proteins, Musashi may exert broad regulatory control over the pituitary proteome in a cell type-specific manner.

Revisiting the gonadotropic regulation of mammalian spermatogenesis: evolving lessons during the past decade

Spermatogenesis is a multi-step process of male germ cell (Gc) division and differentiation which occurs in the seminiferous tubules of the testes under the regulation of gonadotropins - Follicle Stimulating Hormone (FSH) and Luteinising hormone (LH). It is a highly coordinated event regulated by the surrounding somatic testicular cells such as the Sertoli cells (Sc), Leydig cells (Lc), and Peritubular myoid cells (PTc). FSH targets Sc and supports the expansion and differentiation of pre-meiotic Gc, whereas, LH operates via Lc to produce Testosterone (T), the testicular androgen. T acts on all somatic cells e.g.- Lc, PTc and Sc, and promotes the blood-testis barrier (BTB) formation, completion of Gc meiosis, and spermiation. Studies with hypophysectomised or chemically ablated animal models and hypogonadal (hpg) mice supplemented with gonadotropins to genetically manipulated mouse models have revealed the selective and synergistic role(s) of hormones in regulating male fertility. We here have briefly summarized the present concept of hormonal control of spermatogenesis in rodents and primates. We also have highlighted some of the key critical questions yet to be answered in the field of male reproductive health which might have potential implications for infertility and contraceptive research in the future.

Overview of follicle stimulating hormone and its receptors in reproduction and in stem cells and cancer stem cells

Follicle stimulating hormone (FSH) and its receptor (FSHR) have been reported to be responsible for several physiological functions and cancers. The responsiveness of stem cells and cancer stem cells towards the FSH-FSHR system make the function of FSH and its receptors more interesting in the context of cancer biology. This review is comprised of comprehensive information on FSH-FSHR signaling in normal physiology, gonadal stem cells, cancer cells, and potential options of utilizing FSH-FSHR system as an anti-cancer therapeutic target.

Recent updates on animal models for understanding the etiopathogenesis of polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS) is the primary cause of female infertility affecting several women worldwide. Changes in hormonal functions such as hyperandrogenism are considered a significant factor in developing PCOS in women. In addition, many molecular pathways are involved in the pathogenesis of PCOS in women. To have better insights about PCOS, it is data from clinical studies carried on women suffering from PCOS should be collected. However, this approach has several implications, including ethical considerations, cost involved and availability of subject. Moreover, during the early drug development process, it is always advisable to use non-human models mimicking human physiology as they are less expensive, readily available, have a shorter gestation period and less risk involved. Many animal models have been reported that resemble the PCOS pathways in human subjects. However, the models developed on rats and mice are more preferred over other rodent/non-rodent models due to their closer resemblance with human PCOS development mechanism. The most extensively reported PCOS models for rats and mice include those induced by using testosterone, letrozole and estradiol valerate. As the pathophysiology of PCOS is complex, none of the explored models completely surrogates the PCOS related conditions occurring in women. Hence, there is a need to develop an animal model that can resemble the pathophysiology of PCOS in women. The review focuses on various animal models explored to understand the pathophysiology of PCOS. The article also highlights some environmental and food-related models that have been used to induce PCOS.

Hypo-glycosylated hFSH drives ovarian follicular development more efficiently than fully-glycosylated hFSH: enhanced transcription and PI3K and MAPK signaling

STUDY QUESTION

Does hypo-glycosylated human recombinant FSH (hFSH18/21) have greater in vivo bioactivity that drives follicle development in vivo compared to fully-glycosylated human recombinant FSH (hFSH24)?

SUMMARY ANSWER

Compared with fully-glycosylated hFSH, hypo-glycosylated hFSH has greater bioactivity, enabling greater follicular health and growth in vivo, with enhanced transcriptional activity, greater activation of receptor tyrosine kinases (RTKs) and elevated phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and Mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling.

WHAT IS KNOWN ALREADY

Glycosylation of FSH is necessary for FSH to effectively activate the FSH receptor (FSHR) and promote preantral follicular growth and formation of antral follicles. In vitro studies demonstrate that compared to fully-glycosylated recombinant human FSH, hypo-glycosylated FSH has greater activity in receptor binding studies, and more effectively stimulates the PKA pathway and steroidogenesis in human granulosa cells.

STUDY DESIGN, SIZE, DURATION

This is a cross-sectional study evaluating the actions of purified recombinant human FSH glycoforms on parameters of follicular development, gene expression and cell signaling in immature postnatal day (PND) 17 female CD-1 mice. To stimulate follicle development in vivo, PND 17 female CD-1 mice (n = 8-10/group) were treated with PBS (150 µl), hFSH18/21 (1 µg/150 µl PBS) or hFSH24 (1 µg/150 µl PBS) by intraperitoneal injection (i.p.) twice daily (8:00 a.m. and 6:00 p.m.) for 2 days. Follicle numbers, serum anti-Müllerian hormone (AMH) and estradiol levels, and follicle health were quantified. PND 17 female CD-1 mice were also treated acutely (2 h) in vivo with PBS, hFSH18/21 (1 µg) or hFSH24 (1 µg) (n = 3-4/group). One ovary from each mouse was processed for RNA sequencing analysis and the other ovary processed for signal transduction analysis. An in vitro ovary culture system was used to confirm the relative signaling pathways.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The purity of different recombinant hFSH glycoforms was analyzed using an automated western blot system. Follicle numbers were determined by counting serial sections of the mouse ovary. Real-time quantitative RT-PCR, western blot and immunofluorescence staining were used to determine growth and apoptosis markers related with follicle health. RNA sequencing and bioinformatics were used to identify pathways and processes associated with gene expression profiles induced by acute FSH glycoform treatment. Analysis of RTKs was used to determine potential FSH downstream signaling pathways in vivo. Western blot and in vitro ovarian culture system were used to validate the relative signaling pathways.

MAIN RESULTS AND THE ROLE OF CHANCE

Our present study shows that both hypo- and fully-glycosylated recombinant human FSH can drive follicular growth in vivo. However, hFSH18/21 promoted development of significantly more large antral follicles compared to hFSH24 (P < 0.01). In addition, compared with hFSH24, hFSH18/21 also promoted greater indices of follicular health, as defined by lower BAX/BCL2 ratios and reduced cleaved Caspase 3. Following acute in vivo treatment with FSH glycoforms RNA-sequencing data revealed that both FSH glycoforms rapidly induced ovarian transcription in vivo, but hypo-glycosylated FSH more robustly stimulated Gαs and cAMP-mediated signaling and members of the AP-1 transcription factor complex. Moreover, hFSH18/21 treatment induced significantly greater activation of RTKs, PI3K/AKT and MAPK/ERK signaling compared to hFSH24. FSH-induced indices of follicle growth in vitro were blocked by inhibition of PI3K and MAPK.

LARGE SCALE DATA

RNA sequencing of mouse ovaries. Data will be shared upon reasonable request to the corresponding author.

LIMITATIONS, REASONS FOR CAUTION

The observations that hFSH glycoforms have different bioactivities in the present study employing a mouse model of follicle development should be verified in nonhuman primates. The gene expression studies reflect transcriptomes of whole ovaries.

WIDER IMPLICATIONS OF THE FINDINGS

Commercially prepared recombinant human FSH used for ovarian stimulation in human ART is fully-glycosylated FSH. Our findings that hypo-glycosylated hFSH has greater bioactivity enabling greater follicular health and growth without exaggerated estradiol production in vivo, demonstrate the potential for its development for application in human ART.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by NIH 1P01 AG029531, NIH 1R01 HD 092263, VA I01 BX004272, and the Olson Center for Women's Health. JSD is the recipient of a VA Senior Research Career Scientist Award (1IK6 BX005797). This work was also partially supported by National Natural Science Foundation of China (No. 31872352). The authors declared there are no conflicts of interest.

Aberrant and constitutive expression of FOXL2 impairs ovarian development and functions in mice

Development and functions of the ovary rely on appropriate signaling and communication between various ovarian cell types. FOXL2, a transcription factor that plays a key role at different stages of ovarian development, is associated with primary ovarian insufficiency and ovarian cancer as a result of its loss-of-function or mutations. In this study, we investigated the impact of aberrant, constitutive expression of FOXL2 in somatic cells of the ovary. Overexpression of FOXL2 that started during fetal life resulted in defects in nest breakdown and consequent formation of polyovular follicles. Granulosa cell differentiation was impaired and recruitment and differentiation of steroidogenic theca cells was compromised. As a consequence, adult ovaries overexpressing FOXL2 exhibited defects in compartmentalization of granulosa and theca cells, significant decreased steroidogenesis and lack of ovulation. These findings demonstrate that fine-tuned expression of FOXL2 is required for proper folliculogenesis and fertility.

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 Association Study Reveals Candidate Genes for Litter Size Traits in Pelibuey Sheep

The Pelibuey sheep has adaptability to climatic variations, resistance to parasites, and good maternal ability, whereas some ewes present multiple births, which increases the litter size in farm sheep. The litter size in some wool sheep breeds is associated with the presence of mutations, mainly in the family of the transforming growth factor β (TGF-β) genes. To explore genetic mechanisms underlying the variation in litter size, we conducted a genome-wide association study in two groups of Pelibuey sheep (multiparous sheep with two lambs per birth vs. uniparous sheep with a single lamb at birth) using the OvineSNP50 BeadChip. We identified a total of 57 putative SNPs markers (p < 3.0 × 10^-3, Bonferroni correction). The candidate genes that may be associated with litter size in Pelibuey sheep are CLSTN2, MTMR2, DLG1, CGA, ABCG5, TRPM6, and HTR1E. Genomic regions were also identified that contain three quantitative trait loci (QTLs) for aseasonal reproduction (ASREP), milk yield (MY), and body weight (BW). These results allowed us to identify SNPs associated with genes that could be involved in the reproductive process related to prolificacy.

Commentary on the Recent FSH Collection: Known Knowns and Known Unknowns

Follicle-stimulating hormone (FSH) is a dimeric glycoprotein secreted by the anterior pituitary gonadotrope that is necessary for reproductive function in mammals. FSH primarily regulates granulosa cells and follicular growth in females, and Sertoli cell function in males. Since its identification in the 1930s and sequencing in the 1970s, significant progress has been made in elucidating its regulation and downstream function. Recent advances provide deeper insight into FSH synthesis, and effects in the gonads suggest potential roles in extragonadal tissues and examine pharmacological approaches and clinical applications in infertility treatment that now affect 18% of couples. These advances were discussed in detail in a number of reviews published in the last 2 years in Endocrinology. In this brief commentary, we summarize these reviews and point to the outstanding questions that should be answered in the near future to bridge a gap in our understanding of this hormone.