DICER1-mutated rhabdomyosarcoma of the ovary with teratoid features

DICER1-mutated rhabdomyosarcoma is a rare, emerging entity with a predilection for the gynecologic and genitourinary tracts. We report here a case of DICER1-mutated rhabdomyosarcoma of the ovary in a 14 years old girl which displayed interspersed mature teratoid glands, neuroectodermal rosettes and immature blastematous-like tubes. Morphologically the sarcomatous component predominated, corresponding to a high grade spindle cell rhabdomyosarcoma with botryoid features. Islets of cartilage were present. The sarcomatous proliferation encased the teratoid glands, forming cambium layer-like arrangements. The sarcoma cells were Myogenin and MYOD1 positive, the neuroectodermal rosettes expressed SALL4 along with cytokeratins and EMA and were negative for Inhibin; immature blastematous-like tubes were negative for SALL4 and Inhibin. Whole RNA- and targeted DNA-sequencing revealed two DICER1 mutations in exon 26: c.5113G>A: p.(Glu1705Lys) and exon 12: c.1642C>T: p.(Gln548X). The sarcomatous component harbored a complex genetic profile while the teratoid component was diploid, none of the above displayed abnormality of 12p. DICER1-mutated sarcomas display pathological features similar to embryonal rhabdomyosarcomas, botryoid type. They also display heterogeneous features combining cartilage foci, teratoid mature glands, immature blastematous-like tubes and/or neuroectodermal components. Molecular testing remains necessary to confirm the diagnosis. Further studies need to clarify the nosology of DICER1-mutated sarcomas and devise specific therapeutic strategies.

Rescue of bmp15 deficiency in zebrafish by mutation of inha reveals mechanisms of BMP15 regulation of folliculogenesis

As an oocyte-specific growth factor, bone morphogenetic protein 15 (BMP15) plays a critical role in controlling folliculogenesis. However, the mechanism of BMP15 action remains elusive. Using zebrafish as the model, we created a bmp15 mutant using CRISPR/Cas9 and demonstrated that bmp15 deficiency caused a significant delay in follicle activation and puberty onset followed by a complete arrest of follicle development at previtellogenic (PV) stage without yolk accumulation. The mutant females eventually underwent female-to-male sex reversal to become functional males, which was accompanied by a series of changes in secondary sexual characteristics. Interestingly, the blockade of folliculogenesis and sex reversal in bmp15 mutant could be partially rescued by the loss of inhibin (inha-/-). The follicles of double mutant (bmp15-/-;inha-/-) could progress to mid-vitellogenic (MV) stage with yolk accumulation and the fish maintained their femaleness without sex reversal. Transcriptome analysis revealed up-regulation of pathways related to TGF-β signaling and endocytosis in the double mutant follicles. Interestingly, the expression of inhibin/activin βAa subunit (inhbaa) increased significantly in the double mutant ovary. Further knockout of inhbaa in the triple mutant (bmp15-/-;inha-/-;inhbaa-/-) resulted in the loss of yolk granules again. The serum levels of estradiol (E2) and vitellogenin (Vtg) both decreased significantly in bmp15 single mutant females (bmp15-/-), returned to normal in the double mutant (bmp15-/-;inha-/-), but reduced again significantly in the triple mutant (bmp15-/-;inha-/-;inhbaa-/-). E2 treatment could rescue the arrested follicles in bmp15-/-, and fadrozole (a nonsteroidal aromatase inhibitor) treatment blocked yolk accumulation in bmp15-/-;inha-/- fish. The loss of inhbaa also caused a reduction of Vtg receptor-like molecules (e.g., lrp1ab and lrp2a). In summary, the present study provided comprehensive genetic evidence that Bmp15 acts together with the activin-inhibin system in the follicle to control E2 production from the follicle, Vtg biosynthesis in the liver and its uptake by the developing oocytes.

Evolving roles of activins and inhibins in ovarian cancer pathophysiology

Activins and inhibins are unique members of the transforming growth factor-β (TGFβ) family of growth factors, with the ability to exert autocrine, endocrine, and paracrine effects in a wide range of complex physiologic and pathologic processes. Although first isolated within the pituitary, emerging evidence suggests broader influence beyond reproductive development and function. Known roles of activin and inhibin in angiogenesis and immunity along with correlations between gene expression and cancer prognosis suggest potential roles in tumorigenesis. Here, we present a review of the current understanding of the biological role of activins and inhibins as it relates to ovarian cancers, summarizing the underlying signaling mechanisms and physiologic influence, followed by detailing their roles in cancer progression, diagnosis, and treatment.

Loss of growth differentiation factor 9 causes an arrest of early folliculogenesis in zebrafish-A novel insight into its action mechanism

Growth differentiation factor 9 (GDF9) was the first oocyte-specific growth factor identified; however, most information about GDF9 functions comes from studies in the mouse model. In this study, we created a mutant for Gdf9 gene (gdf9-/-) in zebrafish using TALEN approach. The loss of Gdf9 caused a complete arrest of follicle development at primary growth (PG) stage. These follicles eventually degenerated, and all mutant females gradually changed to males through sex reversal, which could be prevented by mutation of the male-promoting gene dmrt1. Interestingly, the phenotypes of gdf9-/- could be rescued by simultaneous mutation of inhibin α (inha-/-) but not estradiol treatment, suggesting a potential role for the activin-inhibin system or its signaling pathway in Gdf9 actions. In gdf9-null follicles, the expression of activin βAa (inhbaa), but not βAb (inhbab) and βB (inhbb), decreased dramatically; however, its expression rebounded in the double mutant (gdf9-/-;inha-/-). These results indicate clearly that the activation of PG follicles to enter the secondary growth (SG) requires intrinsic factors from the oocyte, such as Gdf9, which in turn works on the neighboring follicle cells to trigger follicle activation, probably involving activins. In addition, our data also support the view that estrogens are not involved in follicle activation as recently reported.

Steroidogenic Factor 1 Regulates Transcription of the Inhibin B Coreceptor in Pituitary Gonadotrope Cells

The inhibins control reproduction by suppressing follicle-stimulating hormone synthesis in pituitary gonadotrope cells. The newly discovered inhibin B coreceptor, TGFBR3L, is selectively and highly expressed in gonadotropes in both mice and humans. Here, we describe our initial characterization of mechanisms controlling cell-specific Tgfbr3l/TGFBR3L transcription. We identified two steroidogenic factor 1 (SF-1 or NR5A1) cis-elements in the proximal Tgfbr3l promoter in mice. SF-1 induction of murine Tgfbr3l promoter-reporter activity was inhibited by mutations in one or both sites in heterologous cells. In homologous cells, mutation of these cis-elements or depletion of endogenous SF-1 similarly decreased reporter activity. We observed nearly identical results when using a human TGFBR3L promoter-reporter. The Tgfbr3l gene was tightly compacted and Tgfbr3l mRNA expression was essentially absent in gonadotropes of SF-1 (Nr5a1) conditional knockout mice. During murine embryonic development, Tgfbr3l precedes Nr5a1 expression, though the two transcripts are fully colocalized by embryonic day 18.5 and thereafter. Collectively, these data indicate that SF-1 directly regulates Tgfbr3l/TGFBR3L transcription and is required for postnatal expression of the gene in gonadotropes.

Pituitary gonadotroph-specific patterns of gene expression and hormone secretion

Pituitary gonadotrophs play a key role in reproductive functions by secreting luteinizing hormone (LH) and follicle-stimulating hormone (FSH). The LH secretory activity of gonadotroph is controlled by hypothalamic gonadotropin-releasing hormone (GnRH) via GnRH receptors and is accompanied by only minor effects on high basal Lhb gene expression. The secretory profiles of GnRH and LH are highly synchronized, with the latter reflecting a depletion of prestored LH in secretory vesicles by regulated exocytosis. In contrast, FSH is predominantly released by constitutive exocytosis, and secretory activity reflects the kinetics of Fshb gene expression controlled by GnRH, activin, and inhibin. Here is a review of recent data to improve the understanding of multiple patterns of gonadotroph gene expression and hormone secretion.

Maternal exposure to PM2.5 disrupting offspring spermatogenesis through induced sertoli cells apoptosis via inhibin B hypermethylation in mice

Particulate Matter 2.5 (PM_2.5) disrupts endocrine functions and may negatively affect sperm quality and quantity in males; however, the long-term effects and potential mechanisms of this effect are unknown. This study aimed to investigate the epigenetic mechanism of maternal exposure to PM_2.5-induced inhibin B hypermethylation in male offspring. In this experiment design, pregnant C57BL/6 mice were treated with two doses of PM_2.5 (4.8 and 43.2 mg/kg bw). The membrane control group was given a sampling membrane and the control group received nothing. Following the formation of the vaginal plug, intratracheal instillation of PM_2.5 was administered every three days until delivery of the pups. To assess the effect of PM_2.5 in vitro, TM4 cells, a Sertoli-like cell line, was treated with different concentrations (0, 25, 50, 100 μg/mL) of PM_2.5 for 24 h. The results displayed that Sperm motility, as well as the number of adult offspring, was decreased in the PM_2.5 exposed group relative to the untreated controls. Increased vacuolization was observed in the Sertoli cells of mice that were exposed to PM_2.5 in utero. The levels of inhibin and testosterone were reduced and the levels of LH and FSH increased in the PM_2.5 groups relative to the untreated controls. In vitro, PM_2.5 resulted in cell cycle inhibition as well as increased apoptosis in TM4 cells. Moreover, PM_2.5-induced inhibin B hypermethylation and activation of the p21/Cleaved Caspase-3 pathway resulted in TM4 cell apoptosis that was rescued through the use of a DNA methylation inhibitor. Together, our data suggest that prenatal exposure to PM_2.5 results in inhibin B hypermethylation and can activate the p21/Cleaved Caspase-3 pathway, resulting in Sertoli cell apoptosis, aberrant secretion of androgen binding protein, and decreased testosterone, thus resulting in the inhibition of spermatogenesis.

Testicular Sertoli Cell Hormones in Differences in Sex Development

The Sertoli cells of the testes play an essential role during gonadal development, in addition to supporting subsequent germ cell survival and spermatogenesis. Anti-Müllerian hormone (AMH) is a member of the TGF-β superfamily, which is secreted by immature Sertoli cells from the 8th week of fetal gestation. lnhibin B is a glycoprotein, which is produced by the Sertoli cells from early in fetal development. In people with a Difference or Disorder of Sex Development (DSD), these hormones may be useful to determine the presence of testicular tissue and potential for spermatogenesis. However, fetal Sertoli cell development and function is often dysregulated in DSD conditions and altered production of Sertoli cell hormones may be detected throughout the life course in these individuals. As such this review will consider the role of AMH and inhibin B in individuals with DSD.

Inhibin Inactivation in Female Mice Leads to Elevated FSH Levels, Ovarian Overstimulation, and Pregnancy Loss

Inhibins are members of the transforming growth factor-β family, composed of a common α-subunit disulfide-linked to 1 of 2 β-subunits (βA in inhibin A or βB in inhibin B). Gonadal-derived inhibin A and B act in an endocrine manner to suppress the synthesis of follicle-stimulating hormone (FSH) by pituitary gonadotrope cells. Roles for inhibins beyond the pituitary, however, have proven difficult to delineate because deletion of the inhibin α-subunit gene (Inha) results in unconstrained expression of activin A and activin B (homodimers of inhibin β-subunits), which contribute to gonadal tumorigenesis and lethal cachectic wasting. Here, we generated mice with a single point mutation (Arg233Ala) in Inha that prevents proteolytic processing and the formation of bioactive inhibin. In vitro, this mutation blocked inhibin maturation and bioactivity, without perturbing activin production. Serum FSH levels were elevated 2- to 3-fold in InhaR233A/R233A mice due to the loss of negative feedback from inhibins, but no pathological increase in circulating activins was observed. While inactivation of inhibin A and B had no discernible effect on male reproduction, female InhaR233A/R233A mice had increased FSH-dependent follicle development and enhanced natural ovulation rates. Nevertheless, inhibin inactivation resulted in significant embryo-fetal resorptions and severe subfertility and was associated with disrupted maternal ovarian function. Intriguingly, heterozygous Inha+/R233A females had significantly enhanced fecundity, relative to wild-type littermates. These studies have revealed novel effects of inhibins in the establishment and maintenance of pregnancy and demonstrated that partial inactivation of inhibin A/B is an attractive approach for enhancing female fertility.

Homozygosity for a novel INHA mutation in two male siblings with hypospadias, primary hypogonadism, and high-normal testicular volume

BACKGROUND

The human INHA gene encodes the inhibin subunit alpha protein, which is common to both inhibin A and B. The functional importance of inhibins in male sex development, sexual function, and reproduction remain largely unknown.

OBJECTIVE

We report for the first time two male siblings with homozygous INHAmutations.

METHODS

The medical files were examined for clinical, biochemical, and imaging data. Genetic analysis was performed using next-generation and Sanger sequencing methods.

RESULTS

Two brothers complained of gynecomastia, testicular pain, and had a history of hypospadias. Biochemistry revealed low serum testosterone, high gonadotropin and anti-Mullerian hormone, and very low/undetectable inhibin concentrations, where available. Both patients had azoospermia in the spermiogram. We have identified a homozygous 2 bp deletion (c.208_209delAG, R70Gfs*3) variant, which leads to a truncated INHA protein in both patients, and confirmed heterozygosity in the parents. The external genital development, pubertal onset and progression, reproductive functions, serum gonadotropins, and sex hormones of mother and father, who were heterozygous carriers of the identified mutation, were normal.

CONCLUSION

Homozygosity for INHA mutations causes decreased prenatal and postnatal testosterone production and infertility in males, while the heterozygous female and male carriers of INHA mutations do not have any abnormality in sex development and reproduction.

Human INHBB Gene Variant (c.1079T>C:p.Met360Thr) Alters Testis Germ Cell Content, but Does Not Impact Fertility in Mice

Testicular-derived inhibin B (α/β B dimers) acts in an endocrine manner to suppress pituitary production of follicle-stimulating hormone (FSH), by blocking the actions of activins (β A/B/β A/B dimers). Previously, we identified a homozygous genetic variant (c.1079T>C:p.Met360Thr) arising from uniparental disomy of chromosome 2 in the INHBB gene (β B-subunit of inhibin B and activin B) in a man suffering from infertility (azoospermia). In this study, we aimed to test the causality of the p.Met360Thr variant in INHBB and testis function. Here, we used CRISPR/Cas9 technology to generate InhbbM364T/M364T mice, where mouse INHBB p.Met364 corresponds with human p.Met360. Surprisingly, we found that the testes of male InhbbM364T/M364T mutant mice were significantly larger compared with those of aged-matched wildtype littermates at 12 and 24 weeks of age. This was attributed to a significant increase in Sertoli cell and round spermatid number and, consequently, seminiferous tubule area in InhbbM364T/M364T males compared to wildtype males. Despite this testis phenotype, male InhbbM364T/M364T mutant mice retained normal fertility. Serum hormone analyses, however, indicated that the InhbbM364T variant resulted in reduced circulating levels of activin B but did not affect FSH production. We also examined the effect of this p.Met360Thr and an additional INHBB variant (c.314C>T: p.Thr105Met) found in another infertile man on inhibin B and activin B in vitro biosynthesis. We found that both INHBB variants resulted in a significant disruption to activin B in vitro biosynthesis. Together, this analysis supports that INHBB variants that limit activin B production have consequences for testis composition in males.

circRNA-Mediated Inhibin-Activin Balance Regulation in Ovarian Granulosa Cell Apoptosis and Follicular Atresia

Ovarian granulosa cells (GC) play an essential role in the development and atresia of follicles. Emerging studies suggest that non-coding RNAs are involved in the regulation of GC apoptosis. Here, we aimed to analyze the function of ssc-circINHA-001, coded by the first exon of the inhibin subunit α gene (INHA), in resisting GC apoptosis and follicular atresia by enhancing the expression of the inhibin subunit β A (INHBA) through a cluster of miRNAs. A higher expression of ssc-circINHA-001 in healthy follicles compared to early atretic follicles was detected by qRT-PCR. Its circular structure was confirmed by RNase R treatment and reversed PCR. The function of ssc-circINHA-001 in GC resistance to apoptosis was detected by in vitro transfection of its si-RNA. Furthermore, the dual-luciferase reporter assay suggested that ssc-circINHA-001 adsorbed three miRNAs, termed miR-214-5p, miR-7144-3p, and miR-9830-5p, which share the common target INHBA. A low expression of ssc-circINHA-001 increased the levels of the free miRNAs, inhibited INHBA expression, and thus raised GCs apoptosis through a shift from the secretion of activin to that of inhibin. Our study demonstrated the existence of a circRNA–microRNAs–INHBA regulatory axis in follicular GC apoptosis and provides insight into the relationship between circRNA function and its coding gene in inhibin/activin balance and ovarian physiological functions.

A bioinformatic analysis of the inhibin-betaglycan-endoglin/CD105 network reveals prognostic value in multiple solid tumors

Inhibins and activins are dimeric ligands belonging to the TGFβ superfamily with emergent roles in cancer. Inhibins contain an α-subunit (INHA) and a β-subunit (either INHBA or INHBB), while activins are mainly homodimers of either βA (INHBA) or βB (INHBB) subunits. Inhibins are biomarkers in a subset of cancers and utilize the coreceptors betaglycan (TGFBR3) and endoglin (ENG) for physiological or pathological outcomes. Given the array of prior reports on inhibin, activin and the coreceptors in cancer, this study aims to provide a comprehensive analysis, assessing their functional prognostic potential in cancer using a bioinformatics approach. We identify cancer cell lines and cancer types most dependent and impacted, which included p53 mutated breast and ovarian cancers and lung adenocarcinomas. Moreover, INHA itself was dependent on TGFBR3 and ENG/CD105 in multiple cancer types. INHA, INHBA, TGFBR3, and ENG also predicted patients' response to anthracycline and taxane therapy in luminal A breast cancers. We also obtained a gene signature model that could accurately classify 96.7% of the cases based on outcomes. Lastly, we cross-compared gene correlations revealing INHA dependency to TGFBR3 or ENG influencing different pathways themselves. These results suggest that inhibins are particularly important in a subset of cancers depending on the coreceptor TGFBR3 and ENG and are of substantial prognostic value, thereby warranting further investigation.

Loss of Inhibin Advances Follicle Activation and Female Puberty Onset but Blocks Oocyte Maturation in Zebrafish

Inhibin was first characterized in mammals as a gonadal dimeric protein that inhibited pituitary follicle-stimulating hormone (FSH) secretion. As in mammals, the inhibin-specific α subunit (INHA/Inha/inha) has also been characterized in teleosts; however, its functions and physiological importance in fish reproduction remain unknown. Using CRISPR/Cas9 method, we generated an inha-deficient zebrafish line and analyzed its reproductive performance. As expected, pituitary expression of fshb increased significantly in both the young and the adult inha mutant. The expression of lhb also increased in the mutant, but only in sexually mature adults. Interestingly, the expression of activin βA (inhbaa) increased significantly in both the ovary and the testis of inha mutant, and the expression of ovarian aromatase (cyp19a1a) also increased dramatically in the mutant ovary. The juvenile female mutant showed clear signs of early follicle activation or precocious puberty onset. However, the adult female mutant was infertile with follicles arrested at the full-grown stage without final oocyte maturation and ovulation. Although follicle growth was normal overall in the mutant, the size and distribution of yolk granules in oocytes were distinct and some follicles showed granulosa cell hypertrophy. In contrast to females, inha-null males showed normal spermatogenesis and fertility. As reported in mammals, we also found sporadic tumor formation in inha mutants. Taken together, our study not only confirmed some conserved roles of inhibin across vertebrates, such as inhibition of FSH biosynthesis and tumor formation, but also revealed novel aspects of inhibin functions such as disruption of folliculogenesis and female infertility but no obvious involvement in spermatogenesis in fish.

Association of polymorphism c.-124G>A and c.-16 C>T in the promoter region of human INHA gene with altered sperm parameters; A pilot study

OBJECTIVE

The objective of this was to demonstrate the association of Inhibin α (INHα) c.-124G>A and INHα-c.-16 C>T polymorphisms with altered sperm parameters in a selected male population of Karachi, Pakistan.

STUDY DESIGN & SETTINGS

In this pilot study, male subjects were stratified on the basis of the WHO criteria for altered sperm parameters; 83 (cases-altered sperm parameters) and 30 (controls-normal sperm parameters) subjects were included for analysis of INHα-c.124G>A polymorphism and 88 (cases) and 38 (controls) were analysed for INHα -c-16 C>T polymorphism. Genotyping of INHα-c.-124G>A and INHα-c.-16 C>T was performed by PCR-RFLP, genotype distribution in Hardy-Weinberg equilibrium was evaluated by binary logistic regression model.

RESULTS

For the c.-124G>A polymorphism in INHα gene, frequency of the three major genotypes in controls was: GG: 80.0%, GA: 20.0% and AA: 0% and in cases was: GG: 59.0%, GA: 30.2% and AA: 10.8%. The GG genotype was significantly associated with male infertility (P < .045, OR = 2.776, 95% CI = 1.025-7.513) while the GA genotype was not significantly associated with infertility (P < .290 OR = 0.580, 95% CI = 0.211-1.593). Frequency of mutant AA genotype was 10.8% in cases (altered sperm parameters) and absent (0%) in normal sperm parameter (controls). The frequencies of three major genotypes CC, CT and TT did not show any significant difference between cases and controls (P > .05).

CONCLUSION

The results from our study exhibited a significant association of c.-124G>A polymorphism in the INHα gene promoter region with male infertility in the Pakistani population. A significant association of c.-16 C>T polymorphism with male infertility, however, was not observed. Further large-scale studies should be conducted to confirm this association.

Molecular characterization and expression pattern of inhibin α and βb in Chinese tongue sole (Cynoglossus semilaevis)

Inhibin plays important roles in vertebrate reproduction and development. In this study, we have cloned two genes encoding inhibin subunits, inhα and ihnβb, in Chinese tongue sole. inhα consists of 1032 bp, encoding a 343 amino-acid protein. inhβb is composed of 1275 bp, encoding a 424 amino-acid protein. Phylogenetic tree analysis indicated that INHα and INHβB were independently evolved. qPCR showed that inhα expression of in male testis was higher than that in ovary and pseudomale testis, while the expression of inhβb in ovary was higher than that in male and pseudomale testis. During gonadal developmental stages, inhα expression reached highest at 120 days post hatching (dph) both in ovary and testis, then showed decline in ovary but it was first decreased and then increased in the testis. Similarly, inhβb expression in ovary was low at 50-80 dph. At 120 dph, its expression was significantly increased to the peak level, and then gradually decreased. inhβb expression in testis maintained at a low level. During the embryonic developmental stages, inhα displayed the highest expression at 32-cell stage, whereas inhβb reached the highest expression at blastula stages. In situ hybridization data showed that both of inhα and inhβb were detected in oocytes of all stages. In male testis, inhα and inhβb was localized in spermatogonia, spermatocytes, spermatozoa, sertoli and leydig cells. In pseudomale testis, inhα showed the similar pattern in male testis, while the inhβb was detected in spermatocytes and spermatozoa. These data suggested that inhα may participate the spermatogenesis and oogenesis of Chinese tongue sole, while inhβb might predominantly function in oogenesis.

Engineering the Ovarian Hormones Inhibin A and Inhibin B to Enhance Synthesis and Activity

Ovarian-derived inhibin A and inhibin B (heterodimers of common α- and differing β-subunits) are secreted throughout the menstrual cycle in a discordant pattern, with smaller follicles producing inhibin B, whereas the dominant follicle and corpus luteum produce inhibin A. The classical function for endocrine inhibins is to block signalling by activins (homodimers of β-subunits) in gonadotrope cells of the anterior pituitary and, thereby, inhibit the synthesis of FSH. Whether inhibin A and inhibin B have additional physiological functions is unknown, primarily because producing sufficient quantities of purified inhibins, in the absence of contaminating activins, for preclinical studies has proven extremely difficult. Here, we describe novel methodology to enhance inhibin A and inhibin B activity and to produce these ligands free of contaminating activins. Using computational modeling and targeted mutagenesis, we identified a point mutation in the activin β A-subunit, A347H, which completely disrupted activin dimerization and activity. Importantly, this β A-subunit mutation had minimal effect on inhibin A bioactivity. Mutation of the corresponding residue in the inhibin β B-subunit, G329E, similarly disrupted activin B synthesis/activity without affecting inhibin B production. Subsequently, we enhanced inhibin A potency by modifying the binding site for its co-receptor, betaglycan. Introducing a point mutation into the α-subunit (S344I) increased inhibin A potency ~12-fold. This study has identified a means to eliminate activin A/B interference during inhibin A/B production, and has facilitated the generation of potent inhibin A and inhibin B agonists for physiological exploration.

Inhibin A-A Promising Predictive Parameter for Determination of Final Oocyte Maturation in Ovarian Stimulation for IVF/ICSI

The number of mature oocytes is a key factor in the success of Assisted Reproductive Techniques (ART). Exogenous gonadotropins are administered during ovarian stimulation in order to maximize the number of oocytes available for fertilization. During stimulation, monitoring is mandatory to evaluate individual response, to avoid treatment complications and assist in the determination of the optimal day for final oocyte maturation and oocyte retrieval. Routine monitoring during stimulation includes transvaginal ultrasound examinations and measurement of serum estradiol (E2). Due to multifollicular growth of follicles of varying size, serum E2 levels are commonly supraphysiological and often variable, rendering E2-measurement during ovarian stimulation unreliable as a determinant of oocyte maturity. In contrast to serum E2, serum Inhibin A levels increase once a minimum follicle size of 12-15 mm is achieved. Due to this fact, serum Inhibin A levels could present in combination with ultrasound monitoring a more reliable parameter to determine the optimal follicle size for final oocyte maturation, as only follicles with a size of 12 mm and beyond will contribute to the serum Inhibin A level. This prospective observational, cross-sectional study demonstrates, that on the day of final oocyte maturation serum Inhibin A is strongly correlated to the number of follicles ≥15 mm (0.72) and to the number of retrieved and mature oocytes (ρ 0.82/0.77, respectively), whereas serum E2 is moderately correlated to the parameters mentioned above (ρ 0.64/0.69/0.69, respectively). With an area under the curve (AUC) of 0.91 for Inhibin A, compared to an AUC of 0.84 for E2, Inhibin A can be regarded as a better predictor for the optimal timing of trigger medication with a threshold number of ≥10 mature oocytes. It can be concluded from this data that serum Inhibin A in combination with transvaginal ultrasound monitoring may be a more powerful tool in the decision making process on trigger timing as compared to E2.

A Tale of Two Proteins: Betaglycan, IGSF1, and the Continuing Search for the Inhibin B Receptor

Inhibins are gonadal hormones that suppress follicle-stimulating hormone (FSH) synthesis by pituitary gonadotrope cells. The structurally related activins stimulate FSH by signaling through complexes of type I and type II receptors. Two models of inhibin action were proposed in 2000. First, inhibins function as competitive receptor antagonists, binding activin type II receptors with high affinity in the presence of the TGF-β type III coreceptor, betaglycan. Second, immunoglobulin superfamily, member 1 (IGSF1, then called p120) was proposed to mediate inhibin B antagonism of activin signaling via its type I receptor. These ideas have been challenged over the past few years. Rather than playing a role in inhibin action, IGSF1 is involved in the central control of the thyroid gland. Betaglycan binds inhibin A and inhibin B with high affinity, but only functions as an obligate inhibin A coreceptor in murine gonadotropes. There is likely to be a distinct, but currently unidentified coreceptor for inhibin B.

Acute heat-treatment disrupts inhibin-related protein production and gene expression in the adult rat testis

Heat reversibly disrupts spermatogenesis, but the effects on Sertoli cell (SC) function and inhibin/activin-related proteins are less well-defined. Adult rat testis weights decreased by 40% within 2 weeks after heat-treatment (43 °C, 15 min), due to loss of pachytene spermatocytes and round spermatids. Coincident effects were reduced SC nuclear volume at one week and >50% reduction in expression of several critical SC genes (Inha, Cld11, Gja1, Tjp1, Cldn3) by 2 weeks. Leydig cell steroidogenic enzymes, Cyp11a1, Hsd3b1, were also reduced. Activin gene expression was unaffected at this time, but expression of the activin-binding protein, follistatin (Fst), increased >2-fold. At 4-8 weeks, coincident with the recovery of spermatocytes and early spermatids, but progressive loss of elongated spermatids, most SC genes had recovered; however, testicular activin A was reduced and activin B increased. At 8 weeks, serum inhibin was decreased and, consequently, serum FSH increased. Crucially, germ cell damage was not associated with a significant inflammatory response. At 14 weeks, most testicular parameters had returned to normal, but testis weights remained slightly reduced. These data indicate that, following acute heat-treatment, expression of several key Sertoli and Leydig cell genes declined in parallel with the initial loss of meiotic germ cells, whereas activins were responsive to the subsequent loss of mature spermatids, leading to an increase in testicular activin B production relative to activin A.

Alpha-solanine inhibits cell proliferation via mitochondrial dysfunction and inhibin synthesis in mouse testis In vitro and In vivo

Sertoli and Leydig cells provide key supporting roles in spermatogenesis. Various toxins have been studied in the TM3 and TM4 mouse testis cell lines to identify their regulatory effects. Alpha-solanine (α-solanine), a toxic compound found in the potato, has cytotoxic effects on various cells, including cancer cells. However, the effect of α-solanine on testis function has not been identified. In this study, we verified for the first time the anti-proliferative effect of α-solanine in mouse testes. α-Solanine reduced cell viability in TM3 and TM4 cells and reduced the expression of the cell cycle checkpoint genes Ccnd1 and Ccne1. We also detected changes in the mitochondrial membrane potential (MMP) and in the cytosolic calcium and intracellular signal pathways in both cell lines. α-Solanine induced AKT, P70S6K, S6, ERK1/2, and JNK activation in mouse testis cells. In addition, the inhibition of AKT with a pharmacological inhibitor (LY294002) demonstrated more synergic anti-proliferative effects than in the TM3 and TM4 cell lines treated only with α-solanine. Inha and Inhba mRNA expression also decreased in both cell lines and α-solanine i.p. injected mouse testes. Collectively, the results from this study verify the toxic effects of α-solanine on testes and male reproductive function.

CircINHA resists granulosa cell apoptosis by upregulating CTGF as a ceRNA of miR-10a-5p in pig ovarian follicles

Mammalian ovarian follicular atresia is a complex and fine-regulated biological process with active involvement of connective tissue growth factor (CTGF). The emergence of studies of endogenous non-coding RNAs has raised a new aspect for exploration of the regulatory mechanisms involved in follicular atresia. Here, we aimed to illustrate a circRNA involved in the CTGF regulatory pathway during the apoptosis and follicular atresia of pig granulosa cells (GCs). We first detected a decreased expression pattern of CTGF during follicular atresia using IHC, FISH and qRT-PCR and confirmed the anti-apoptosis effect of CTGF in GCs in vitro by CTGF siRNA knockdown. Then, we used a dual luciferase activity assay to demonstrate CTGF as a direct functional target of miR-10a-5p, which was upregulated in atresic follicles and promoted the apoptosis of GCs in vitro. The negative effect of miR-10a-5p on GC viability was confirmed by cell cycle assays, cell proliferation/apoptosis assays and the WB detection of marker proteins. More importantly, we identified a novel circRNA, termed circINHA, that was downregulated during atresia in ovarian follicles, and we confirmed a direct interaction between miR-10a-5p and circINHA. Finally, we demonstrated that circINHA promoted GCs proliferation and inhibited GCs apoptosis via CTGF as a competing endogenous RNA (ceRNA) that directly bound to miR-10a-5p. Taken together, this study provides evidence for the circINHA/miR-10a-5p/CTGF regulatory pathway in follicular GC apoptosis and provides novel insights into the role of circRNAs in the modulation of ovarian physiological functions.

The Activin Social Network: Activin, Inhibin, and Follistatin in Breast Development and Cancer

Activins and inhibins are closely related protein heterodimers with a similar tissue distribution; however, these two complexes have opposing functions in development and disease. Both are secreted cytokine hormones, with activin the primary inducer of downstream signaling cascades and inhibin acting as a rheostat that exquisitely governs activin function. Adding to the complexity of activin signaling, follistatin, a highly glycosylated monomeric protein, binds activin with high affinity and restrains downstream pathway activation but through a mechanism distinct from that of inhibin. These three proteins were first identified as key ovarian hormones in the pituitary-gonadal axis that direct the synthesis and secretion of FSH from the pituitary, hence controlling folliculogenesis. Research during the past 30 years has expanded the roles of these proteins, first by discovering the ubiquitous expression of the trio and then by implicating them in a wide array of biological functions. In concert, these three hormones govern tissue development, homeostasis, and disease in multiple organ systems through diverse autocrine and paracrine mechanisms. In the present study, we have reviewed the actions of activin and its biological inhibitors, inhibin, and follistatin, in mammary gland morphogenesis and cancer.

Noonan syndrome males display Sertoli cell-specific primary testicular insufficiency

Context Abnormalities in the hypothalamo-pituitary-gonadal axis have long been reported in Noonan syndrome (NS) males with only few data available in prepubertal children. Objective The aim of this study was to describe the gonadal function of NS males from childhood to adulthood. Design It is a retrospective chart review. Patients and methods A total of 37 males with a genetically confirmed diagnosis of NS were included. Clinical and genetic features, as well as serum hormone levels (LH, FSH, testosterone, anti-Müllerian hormone (AMH), and inhibin B) were analysed. Results Of the 37 patients, 16 (43%) children had entered puberty at a median age of 13.5 years (range: 11.4-15.0 years); age at pubertal onset was negatively correlated with BMI SDS (r = -0.541; P = 0.022). In pubertal boys, testosterone levels were normal suggesting a normal Leydig cell function. In contrast, NS patients had significant lower levels of AMH (mean SDS: -0.6 ± 1.1; P = 0.003) and inhibin B (mean SDS: -1.1 ± 1.2; P < 0.001) compared with the general population, suggesting a Sertoli cell dysfunction. Lower AMH and inhibin B levels were found in NS-PTPN11 patients, whereas these markers did not differ from healthy children in SOS1 patients. No difference was found between cryptorchid and non-cryptorchid patients for AMH and inhibin B levels (P = 0.43 and 0.62 respectively). Four NS-PTPN11 patients had a severe primary hypogonadism with azoospermia/cryptozoospermia. Conclusions NS males display Sertoli cell-specific primary testicular insufficiency, whereas Leydig cell function seems to be unaffected.

Activin over-expression in the testis of mice lacking the inhibin α-subunit gene is associated with androgen deficiency and regression of the male reproductive tract

Regionalised interaction of the activins, follistatin and inhibin was investigated in the male reproductive tract of mice lacking the inhibin α-subunit (Inha^-/-). Serum and intratesticular activin B, although not activin A and follistatin, were increased in Inha^-/- mice at 25 days of age, but all three proteins were elevated at 56 days. None of these proteins were altered within the epididymis and vas deferens at either age. At 25 days, histology of the epididymis and vas deferens was similar to wild-type. At 56 days, the testis contained extensive somatic cell tumours, leading to Leydig cell regression and testosterone deficiency. The epididymis and vas deferens showed epithelial regression and increased prominence of the interstitial stroma. Immunoregulatory and fibrotic gene expression in the epididymis and vas deferens were unchanged. Thus, absence of the inhibin α-subunit has marginal effects on activins in the epididymis and vas deferens, and regression of these tissues is associated with androgen deficiency.

Molecular characterization of inhibin-A: Structure and expression analysis in Clarias batrachus

The inhibins are disulphide-linked heterodimeric glycoproteins that belong to the TGFβ superfamily. Inhibins have been well studied in mammals but the information about their structure and function is very limited in lower vertebrates. The aim of the present study was to characterize inhibin-A and to understand its receptor binding interaction, and to evaluate its biological function in Clarias batrachus. Structure prediction of inhibin-A revealed two glycosylation sites on inhibin-α (Asp262 and Asn334). Docking of inhibin-A with its receptor; betaglycan and Act RIIA showed that residues Ser321, Gly324 and Leu325 of inhibin-α are involved in high affinity binding with betaglycan while inhibin-βA bound to Act RIIA by forming hydrogen bonds. The mRNA transcript analysis of various tissues indicated the presence of higher to moderate expression of inhibin-α and inhibin-βA in the gonads and the extra-gonadal tissues. Further, stage specific expression showed decreased levels of inhibin-α in the gonads during the annual reproductive cycles. Inhibin-βA, activin-βB and Act RIIA increased in the brain during spawning while FSHr increased in the gonads during the preparatory phase. Our study provides molecular, structural and functional insights of inhibin-A for the first time in C. batrachus.

FOXL2C134W-Induced CYP19 Expression via Cooperation With SMAD3 in HGrC1 Cells

Germline knockout studies in female mice demonstrated an essential role for forkhead box L2 (FOXL2) in early follicle development, whereas an inducible granulosa cell (GC)-specific deletion of Foxl2 in adults has shown ovary-to-testis somatic sex reprogramming. In women, over 120 different germline mutations in the FOXL2 gene have been shown to cause blepharophimosis/ptosis/epicantus inversus syndrome associated with or without primary ovarian insufficiency. By contrast, a single somatic mutation (FOXL2C134W) accounts for almost all adult-type GC tumors (aGCTs). To test the hypothesis that FOXL2C134W differentially regulates the expression of aGCT markers, we investigated the effect of FOXL2C134W on inhibin B and P450 aromatase expression using a recently established human GC line (HGrC1), which we now show to bear two normal alleles of FOXL2. Neither FOXL2wt nor FOXL2C134W regulate INHBB messenger RNA (mRNA) expression. However, FOXL2C134W selectively displays a 50-fold induction of CYP19 mRNA expression dependent upon activin A. Mechanistically, the CYP19 promoter is activated in a similar way by FOXL2C134W interaction with SMAD3, but not by FOXL2wt. SMAD2 had no effect. Moreover, FOXL2C134W interactions with SMAD3 and with the FOX binding element located at -199 bp upstream of the ATG initiation codon of CYP19 are more sustainable than FOXL2wt. Thus, FOXL2C134W potentiates CYP19 expression in HGrC1 cells via enhanced recruitment of SMAD3 to a proximal FOX binding element. These findings may explain the pathophysiology of estrogen excess in patients with aGCT.

Molecular characterisation of isoniazid resistant clinical isolates of Mycobacterium tuberculosis from Khyber Pakhtunkhwa, Pakistan

OBJECTIVE

To investigate the frequency of mutations in catalase-peroxidase and inhibin alpha genes in clinical isolates of isoniazid resistant Mycobacterium tuberculosis strains.

METHODS

The study was conducted at Provincial Tuberculosis Reference Laboratory, Peshawar, Pakistan, from April 2015 to March 2016, and comprised sputum specimens obtained from patients of different ages. All the isolates were analysed for isoniazid resistance. Thirty resistant isolates were randomly selected for mutation analysis of the hotspot regions of catalase-peroxidase and inhibin alpha genes.

RESULTS

Of the 163 positive isolates, 79(48.46%) were resistant to isoniazid. Among these, 21(70%) had mutation in catalase-peroxidase gene and 2(6.6%) had C15T mutation in inhibin alpha promoter region. Among the 21 catalase-peroxidase mutants, Ser315Thr mutation was detected in 15(71.4%) isolates. Gly316Ser mutation was detected in 3(14.2%) isolates. Ser315Arg mutation was identified in 2(9.5%) isolates. Double mutation of Ser303Trp and Lys274Arg was detected in 1(4.7%) isolate. Among the inhibin alpha promoter region mutations, 2(6.6%) of the thirty isolates had the most common C15T mutation in the promoter region.

CONCLUSIONS

One novel mutation at codon 303 in catalase-peroxidase gene was found in the study, and it could contribute to isoniazid resistance.

Developmental tracing of oocyte development in gonadal soma-derived factor deficiency medaka (Oryzias latipes) using a transgenic approach

Gonadal soma-derived factor (gsdf) is reported to be a male initiator in medaka based on loss- and gain- of function via targeted disruption, or transgenic over-expression. However, little is known about how gsdf promotes undifferentiated gonad entry into male pathways or prevents entry into the female pathway. We utilized a visible folliculogenesis system with a reporter cassette of dual-color fluorescence expression to identify difference between oocyte development from wildtype and gsdf deficiency medaka. A red fluorescent protein (RFP) is driven by a major component of the synaptonemal complex (SYCP3) promoter which enables RFP expression solely in oocytes after the onset of meiosis, and a histone 2b-EGFP fused protein (H2BEGFP) under the control of an elongation factor (EF1α) promoter, wildly used as a mitotic reporter of cell cycle. This mitosis-meiosis visible switch revealed that early meiotic oocytes present in gsdf deficiency were more than those in wildtype ovaries, corresponding to the decrease of inhibin expression detected by real-time qPCR analysis, suggesting gsdf is tightly involved in the process of medaka oocyte development at early stage.

Endogenous inhibins regulate steroidogenesis in mouse TM3 Leydig cells by altering SMAD2 signalling

This study tested the hypothesis that inhibins act in an autocrine manner on Leydig cells using a pre-pubertal Leydig cell line, TM3, as a model of immature Leydig cells. The expression of Inha, Inhba, and Inhbb in TM3 cells was determined by RT-PCR and the production of the inhibin-alpha subunit was confirmed by western blot. Knockdown of Inha expression resulted in significant decreases in the expression of Leydig cell markers Cyp17a1, Cyp11a1, Nr5a1, and Insl3. Western blot showed that activin A, TGFβ1 and TGFβ2 activated SMAD2, and that knockdown of Inha expression in TM3 cells enhanced both activin A- and TGFβ-induced SMAD2 activation. SB431542, a chemical inhibitor of the TGFβ/activin type I receptors, blocked ligand-induced SMAD2 activation and the downregulation of Cyp17a1 expression. Our findings demonstrate that TGFβs and activin A negatively regulate steroidogenic gene expression in TM3 cells via ALK4/5 and SMAD2 and endogenous inhibins can counter this regulation.

Leydig Cell Tumor of the Testis With Histological and Immunohistochemical Features of Malignancy in a 1-Year-Old Boy With Isosexual Pseudoprecocity

The article reports the clinical, histopathological, and immunohistochemical findings of a 1-year-old boy presenting with isosexual pseudoprecocity attributable to a functioning Leydig cell tumor of the testis. The case appears to represent the youngest patient ever recognized with this well-known syndrome. Malignancy features were also for the first time initially assessed using criteria, retrospectively developed from the literature, for metastasizing Leydig cell tumor. All the following were found: infiltrative borders, cellular pleomorphism, high mitotic index (12-14/high-power field), high MIB-1 index (40%), P53 positivity in 50% of the cells, and bcl-2 positivity in 15% of the cells. Immunohistochemistry proved the cells of the tumor to be positive for inhibin, Melan-A, synaptophysin, cytokeratin, and calretinin and negative for S-100 and chromogranin A. Notably, lipochrome and crystals of Reinke were not found in the tumor cells. Although the neoplasm fulfilled the criteria for a potentially metastasizing Leydig cell tumor, there was no evidence of that event having occurred, perhaps as a result of early treatment or as indication that criteria developed for Leydig cell tumor of adults may not apply to children.

Testicular Juvenile Granulosa Cell Tumor in a Newborn: Case Report and Review of the Literature

Juvenile granulosa cell tumor of the testis of neonates and infants is an uncommon lesion frequently associated with abnormal sex chromosome and ambiguous genitalia. This report describes a juvenile granulosa cell tumor arising in the testis of a neonate. Chromosome analysis of the tumor showed a normal male karyotype 46 XY. Histopathology and immunohistochemical studies revealed the occurrence of 2 well-differentiated epithelial-like and smooth muscle-like components in the neoplasm. The morphologic clues leading to the correct diagnosis of juvenile granulosa cell tumor and the possible histogenesis are briefly discussed.

Global deletion of Trp53 reverts ovarian tumor phenotype of the germ cell-deficient white spotting variant (Wv) mice

White spotting variant (Wv) mice are spontaneous mutants attributed to a point mutation in the c-Kit gene, which reduces the tyrosine kinase activity to around 1% and affects the development of melanocytes, mast cells, and germ cells. Homozygous mutant mice are sterile but can live nearly a normal life span. The female Wv mice have a greatly reduced ovarian germ cell and follicle reserve at birth, and the remaining follicles are largely depleted soon after the females reach reproductive stage at around 7 weeks of age. Consequently, ovarian epithelial tumors develop in 100% of Wv females by 3 to 4 months of age. These tumors, called tubular adenomas, are benign but can become invasive in older Wv mice.

We tested if additional genetic mutation(s) could convert the benign ovarian epithelial tumors to malignant tumors by crossing the Wv mutant into the Trp53 knockout background. Surprisingly, we found that global deletion of Trp53 suppressed the development of ovarian tubular adenomas in Wv mice. The ovaries of Wv/Wv; Trp53 (−/−) mice were covered by a single layer of surface epithelium and lacked excessive epithelial proliferation. Rather, the ovaries contained a small number of follicles. The presence of ovarian follicles and granulosa cells, as indicated by Pgc7 and inhibin-alpha expression, correlated with the absence of epithelial lesions. A reduction of Pten gene dosage, as in Wv/Wv; Pten (+/−) mice, produced a similar, though less dramatic, phenotype. We conclude that deletion of Trp53 prolongs the survival of ovarian follicles in Wv mice and consequently prevents the proliferation of ovarian epithelial cells and development of ovarian tubular adenomas. The results suggest that various cell types within the ovary communicate and mutually modulate, and an intact tissue environment is required to ensure homeostasis of ovarian surface epithelial cells. Especially, the current finding emphasizes the importance of ovarian follicles in suppressing the hyperplastic growth of ovarian epithelial cells, dominating over the loss of p53.

New insights into implication of the SLIT/ROBO pathway in the prehierarchical follicle development of hen ovary

The SLIT/Roundabout (ROBO) pathway is involved in follicle development of mammalian ovary, and 2 secreted hormones activin A and inhibin A have potential roles in modulation of the SLIT/ROBO system, but the related actions remain poorly understood in bird. The aims of the present study were to examine the spatial and temporal expression of the SLIT ligand genes (SLIT1, SLIT2, and SLIT3) and their receptor ROBO1, ROBO2, ROBO3, and ROBO4 genes in various-sized prehierarchical follicles during hen ovary development and the effects of activin A and inhibin A on the expression of these genes in the cultured hen follicles. Our result demonstrated that the transcripts of the 3 SLIT genes were highly expressed in the developing follicles and expression patterns of the SLIT transcripts were different from those of ROBO genes detected by real-time quantitative reverse transcriptase PCR. Both SLIT and ROBO transcripts were predominantly expressed in oocytes and granulosa cells from the prehierarchichal follicles examined by in situ hybridization. The localization for SLIT and ROBO proteins was revealed by immunohistochemistry similar to the spatial distribution of their transcript. In cultured follicles (4 to 8 mm in diameter), the expression levels of SLIT and ROBO members are hormonally regulated by activin A (10 ng/mL) and/or inhibin A (20 ng/mL) after treatment for 24 h. However, the expression of only SLIT2, SLIT3, and ROBO3 mRNA presented a directly opposite response to activin A and inhibin A hormones. These results indicate that SLIT/ROBO pathway is implicated in the prehierarchical follicular development of the hen ovary by an intrafollicular autocrine and/or paracrine action, and is influenced by activin A and inhibin A hormones.

RNAi-mediated knockdown of inhibin α subunit increased apoptosis in granulosa cells and decreased fertility in mice

Inhibin α (INHα), a member of TGFβ superfamily, is an important modulator of reproductive function that plays a vital role in follicular changes, cell differentiation, oocyte development, and ultimately in mammalian reproduction. However, the role of inhibin α in female fertility and ovarian function remains largely unknown. To define its role in reproduction, transgenic mice of RNAi-INHα that knock down the INHα expression by shRNAi were used. Inhibin α subunit gene was knocked down successfully at both transcriptional and translational levels by RNAi PiggyBac transposon (Pbi) mediated recombinant pshRNA vectors and purified DNA fragments were microinjected into mouse zygotes. Results showed that transgenic female mice were sub-fertile and exhibited 35.28% reduction in litter size in F1 generation relative to wild type. The decreased litter size associated with the reduction in the number of oocytes ovulated after puberty. Serum INHα level was significantly decreased in both 3 and 6 weeks; whereas, FSH was significantly increased in 3 weeks but not in 6 weeks. Furthermore, suppression of INHα expression significantly promoted apoptosis by up-regulating Caspase-3, bcl2, INHβB and GDF9 and down regulated Kitl and TGFβRIII genes both at transcriptional and translational levels. Moreover, it also dramatically reduced the progression of G1 phase of cell cycle and the number of cells in S phase as determined by flow cytometer. These results indicate that suppression of INHα expression in RNAi-transgenic mice leads to disruption of normal ovarian regulatory mechanism and causes reproductive deficiencies by promoting cellular apoptosis, arresting cellular progression and altering hormonal signaling.

Inhibin Biosynthesis and Activity Are Limited by a Prodomain-Derived Peptide

Gonadal-derived inhibin A and B are essential factors in mammalian reproduction, negatively regulating pituitary production of FSH. Inhibins are synthesized as heterodimers of α- and β-subunits, each comprising an N-terminal pro- and C-terminal mature domain. After dimerization, the inhibin α- and β-subunit prodomains are enzymatically cleaved from the mature domains at consensus RXXR sites (site1). Interestingly, the inhibin α-subunit is a unique TGF-β ligand, comprising a second cleavage site (site2) within its prodomain. Cleavage at site2 in the inhibin α-subunit prodomain releases a 43-amino acid proα-peptide. We aimed to determine the influence of the proα-peptide on inhibin synthesis and bioactivity. Blocking proα-peptide release by silencing cleavage site2 (Arg56-Arg61) inhibited both inhibin A and B synthesis. Ligand blot analysis and solid-phase binding assays indicated that the proα-peptide binds specifically to a mature 30-kDa inhibin (mean Kd 86 nM) but was unable to bind related activins. The proα-peptide suppressed inhibin A and B bioactivity in primary rat pituitary cell cultures. Mechanistically, the proα-peptide blocked inhibin A binding to its coreceptor, betaglycan (IC50 131 nM), and the subsequent sequestration of the activin type II receptor (IC50 156 nM), which underscores inhibin's biological activity. Based on the sequential mutations across the inhibin α-subunit, the proα-peptide binding site was localized to residues Arg341-Thr354, corresponding directly to the betaglycan binding region. Together our findings indicate that the proα-peptide limits the synthesis and bioactivity of inhibins.

Murine Inhibin α-Subunit Haploinsufficiency Causes Transient Abnormalities in Prepubertal Testis Development Followed by Adult Testicular Decline

Activin production and signaling must be strictly regulated for normal testis development and function. Inhibins are potent activin inhibitors; mice lacking the inhibin-α gene (Inha-/- mice) cannot make inhibin and consequently have highly elevated activin and FSH serum concentrations and excessive activin signaling, resulting in somatic gonadal tumors and infertility. Dose-dependent effects of activin in testicular biology have been widely reported; hence, we hypothesized that male mice lacking one copy of the Inha gene would produce less inhibin and have an abnormal reproductive phenotype. To test this, we compared hormone concentrations, testis development, and sperm production in Inha+/+ and Inha+/- mice. Serum and testicular inhibin-α concentrations in adult Inha+/- mice were approximately 33% lower than wild type, whereas activin A, activin B, FSH, LH, and T were normal. Sixteen-day-old Inha+/- mice had a mixed phenotype, with tubules containing extensive germ cell depletion juxtaposed to tubules with advanced Sertoli and germ cell development. This abnormal phenotype resolved by day 28. By 8 weeks, Inha+/- testes were 11% larger than wild type and supported 44% greater daily sperm production. By 26 weeks of age, Inha+/- testes had distinct abnormalities. Although still fertile, Inha+/- mice had a 27% reduction in spermatogenic efficiency, a greater proportion of S-phase Sertoli cells and lower Leydig cell CYP11A1 expression. This study is the first to identify an intratesticular role for inhibin/inhibin-α subunit, demonstrating that a threshold level of this protein is required for normal testis development and to sustain adult somatic testicular cell function.

Inhibin alpha-subunit (INHA) expression in adrenocortical cancer is linked to genetic and epigenetic INHA promoter variation

Adrenocortical carcinoma (ACC) is a rare, but highly malignant tumor of unknown origin. Inhibin α-subunit (Inha) knockout mice develop ACCs following gonadectomy. In man, INHA expression varies widely within ACC tissues and its circulating peptide inhibin pro-αC has been described as a novel tumor marker for ACC. We investigated whether genetic and epigenetic changes of the INHA gene in human ACC cause loss or variation of INHA expression. To this end, analyses of INHA sequence, promoter methylation and mRNA expression were performed in human adrenocortical tissues. Serum inhibin pro-αC levels were also measured in ACC patients. INHA genetic analysis in 37 unique ACCs revealed 10 novel, heterozygous rare variants. Of the 3 coding bases affected, one variant was synonymous and two were missense variants: S72F and S184F. The minor allele of rs11893842 at -124 bp was observed at a low frequency (24%) in ACC samples and was associated with decreased INHA mRNA levels: 4.7±1.9 arbitrary units for AA, compared to 26±11 for AG/GG genotypes (P = 0.034). The methylation of four proximal INHA promoter CpGs was aberrantly increased in five ACCs (47.7±3.9%), compared to normal adrenals (18.4±0.6%, P = 0.0052), whereas the other 14 ACCs studied showed diminished promoter methylation (9.8±1.1%, P = 0.020). CpG methylation was inversely correlated to INHA mRNA levels in ACCs (r = -0.701, p = 0.0036), but not associated with serum inhibin pro-αC levels. In conclusion, aberrant methylation and common genetic variation in the INHA promoter occur in human ACCs and are associated with decreased INHA expression.

Gonadectomy-related adrenocortical tumors in ferrets demonstrate increased expression of androgen and estrogen synthesizing enzymes together with high inhibin expression

The 2 objectives of this study were to (1) measure by quantitative polymerase chain reaction the expression of genes involved in steroid and inhibin synthesis in adrenocortical tumors of gonadectomized ferrets and (2) localize by immunohistochemistry several proteins that are key to adrenal steroidogenesis. Relative to the control adrenals, expression of the messenger RNAs encoding StAR (steroidogenic acute regulatory protein; P = 0.039), CYP11A (P = 0.019), CYP21 (P = 0.01), and 3β-HSD (P = 0.004), all involved in the synthesis of mineralocorticoids and glucocorticoids, were decreased in the adrenocortical tumors. In contrast, expression of cytochrome B5 (CytB5; P = 0.0001) and aromatase (P = 0.003), involved in androgen and estrogen synthesis, and both inhibin α-subunit (P = 0.002) and βB-subunit (P = 0.001) were upregulated. In tumors, immunostaining of CYP21 was low, whereas staining of Cyp17 and CytB5, necessary for androgen synthesis, was present. It is concluded that ferret adrenocortical tumors express genes for androgen production. In addition, the expression of aromatase and inhibin suggests an even more gonadal differentiation, which is reminiscent to the fact that both gonads and adrenals are derived from a common urogenital primordial cell.

GnRH agonist vs. hCG for triggering of ovulation--differential effects on gene expression in human granulosa cells

OBJECTIVE

To investigate the mRNA expression of genes related to steroidogenesis and OHSS in granulosa cells (GCs) of patients triggered with GnRH agonist compared to patients triggered with hCG.

DESIGN

Mural GCs were obtained at the time of oocyte retrieval and gene expression was analyzed using quantitative real time RT-PCR.

SETTINGS

Single center, case control study.

PATIENT(S)

24 women who were treated with GnRH agonist or hCG for triggering of ovulation.

INTERVENTIONS

GC collection.

MAIN OUTCOME MEASURE(S)

The expression of genes related to steroidogenesis and OHSS in mural GCs.

RESULTS

The fertilization rate was similar in the two groups. The mRNA expression of CYP19A1 (0.50 vs 1, arbitrary unit), CYP11A1 (0.6 vs. 1) and 3 beta hydroxysteroid-dehydrogenase (0.39 vs 1) was significantly lower in the GnRH group. The expression of VEGF (0.74 vs. 1) and inhibin β B (0.38 vs 1) was lower in the GnRH analog triggered group.

CONCLUSION

Expression of genes related to steroidogenesis is lower at the time of oocyte retrieval in patients triggered with GnRH agonist. The decreased expression of VEGF and inhibin β B in the GnRH agonist group can explain the mechanism of early OHSS prevention.

Transgenic mice expressing inhibin α-subunit promoter (inhα)/Simian Virus 40 T-antigen (Tag) transgene as a model for the therapy of granulosa cell-derived ovarian cancer

Granulosa cell tumors are rare, 3-7.6% of primary ovarian tumors, although with poor prognosis as the tumor-related mortality rate is 37.3%, with 80% of deaths occurring on recurrence. We have created a transgenic (TG) murine model for gonadal somatic cell tumors by expressing the powerful viral oncogene, Simian Virus 40 T-antigen (Tag), under the regulation of murine inhibin α-subunit 6 kb promoter (inhα/Tag). Gonadotropin dependent ovarian granulosa cell tumors were formed in females by the age of 5-6 months, with a 100% penetrance. We have successfully used the inhα/Tag model to test different treatment strategies for ovarian tumors. With a gene therapy trial in inhα/Tag mice crossbred with inhα/HSV-TK (herpes simplex virus thymidine kinase) mice (double TG), we proved the principle that targeted expression of HSV-TK gene in gonadal somatic cell tumors enabled tumor ablation by anti-herpes treatment. When we aimed at targeted destruction of luteinizing hormone/chorionic gonadotropin receptor (LHCGR) expressing inhα/Tag tumor cells in vivo by a lytic peptide Hecate-CGβ conjugate, we could successfully kill the tumor cells, sparing the normal cells. We recently found high zona pellucida glycoprotein 3 (ZP3) expression in inhα/Tag granulosa cell tumors, as well as in human granulosa cell tumors. We tested the concept of treating the ovarian tumors of inhα/Tag mice by vaccination against the ectopically expressed ZP3. Immunotherapy with recombinant human (rh) ZP3 was highly successful with no objective side effects in inhα/Tag females, suggesting rhZP3 immunization as a novel strategy for the immunotherapy of ovarian granulosa cell tumors.

Anti-Müllerian hormone (AMH), inhibin-α, growth differentiation factor 9 (GDF9), and bone morphogenic protein-15 (BMP15) mRNA and protein are influenced by photoperiod-induced ovarian regression and recrudescence in Siberian hamster ovaries

Exposure of Siberian hamsters to short photoperiod (SD) inhibits ovarian function, including folliculogenesis, whereas function is restored with their transfer to long photoperiods (LD). To investigate the mechanism of photo-stimulated recrudescence, we assessed key folliculogenic factors-anti-Müllerian hormone (AMH), inhibin-α, growth differentiation factor-9 (GDF9), and bone morphogenic protein-15 (BMP15)-across the estrus cycle and in photo-regressed and recrudescing ovaries. Adult hamsters were exposed to either LD or SD for 14 weeks, which respectively represent functional and regressed ovaries. Select regressed hamsters were transferred back to LD for 2 (post-transfer week 2; PTw2) or 8 weeks (PTw8). Ovaries were collected and fixed in formalin for immunohistochemistry or frozen in liquid nitrogen for real-time PCR. AMH, inhibin-α, GDF9, and BMP15 mRNA and protein were detected in all stages of the estrus cycle. Fourteen weeks of SD exposure increased (P < 0.05) ovarian AMH, GDF9, and BMP15, but not inhibin-α mRNA levels as compared to LD. Transfer of regressed hamsters to stimulatory long photoperiod for 8 weeks returned AMH and GDF9 mRNA levels to LD-treated levels, and further increased mRNA levels for inhibin-α and BMP15. Immunostaining for AMH, inhibin-α, GDF9, and BMP15 proteins was most intense in preantral/antral follicles and oocytes. The overall immunostaining extent for AMH and inhibin-α generally mirrored the mRNA data, though no changes were observed for GDF9 or BMP15 immunostaining. Shifts in mRNA and protein levels across photoperiod conditions suggest possible syncretic roles for these folliculogenic factors in photo-stimulated recrudescence via potential regulation of follicle recruitment, preservation, and development.

Protein kinase C-induced activin A switches adrenocortical steroidogenesis to aldosterone by suppressing CYP17A1 expression

Functional zonation of the adrenal cortex is a consequence of the zone-specific expression of P450c17 (CYP17A1) and its cofactors. Activin and inhibin peptides are differentially produced within the zones of the adrenal cortex and have been implicated in steroidogenic control. In this study, we investigated whether activin and inhibin can function as intermediates in functional zonation of the human adrenal cortex. Activin A suppressed CYP17A1 expression and P450c17 function in adrenocortical cell lines as well as in primary adrenal cell cultures. Inhibin βA-subunit mRNA and activin A protein levels were found to be increased up to 1,900-fold and 49-fold, respectively, after protein kinase C (PKC) stimulation through PMA or angiotensin II in H295R adrenocortical carcinoma cells. This was confirmed in HAC15 cells and for PMA in primary adrenal cell cultures. Both PMA and Ang II decreased CYP17A1 expression in the adrenocortical cell lines, whereas PMA concurrently suppressed CYP17A1 levels in the primary cultures. Inhibition of activin signaling during PKC stimulation through silencing of the inhibin βA-subunit or blocking of the activin type I receptor opposed the PMA-induced downregulation of CYP17A1 expression and P450c17 function. In contrast, PKA stimulation through adrenocorticotrophin or forskolin increased expression of the inhibin α-subunit and betaglycan, both of which are antagonists of activin action. These data indicate that activin A acts as a PKC-induced paracrine factor involved in the suppression of CYP17A1 in the zona glomerulosa and can thereby contribute to functional adrenocortical zonation.

Non-linear association between androgen receptor CAG and GGN repeat lengths and reproductive parameters in fertile European and Inuit men

Recently the dogma that there is an inverse linear association between androgen receptor (AR) CAG and GGN polymorphisms and receptor activity has been challenged. We analysed the pattern of association between 21 male reproductive phenotypes and AR CAG/GGN repeat lengths in 557 proven-fertile men. A linear association was only found between sperm DNA fragmentation index (DFI) and CAG length, and between inhibin B and GGN length. Men with longer CAG then the reference (22-24), had higher oestradiol levels, whereas men with shorter CAG stretches had a higher DFI and a higher proportion of Fas-positive germ cells. Subjects with either short or long CAG had increased seminal levels of prostate-specific antigen and neutral α-glucosidase activity. Compared to men with the median GGN length of 23, those with shorter GGN repeats had higher levels of inhibin B, higher proportions of normal and progressive sperm, and a higher fraction of Fas-positive sperm, while men with longer GGN had higher oestradiol levels. These data indicate that at least for some markers of male reproductive function the association with CAG or GGN repeat length is curvilinear.

DNA methylation and histone modifications are associated with repression of the inhibin α promoter in the rat corpus luteum

The transition from follicle to corpus luteum after ovulation is associated with profound morphological and functional changes and is accompanied by corresponding changes in gene expression. The gene encoding the α subunit of the dimeric reproductive hormone inhibin is maximally expressed in the granulosa cells of the preovulatory follicle, is rapidly repressed by the ovulatory LH surge, and is expressed at only very low levels in the corpus luteum. Although previous studies have identified transient repressors of inhibin α gene transcription, little is known about how this repression is maintained in the corpus luteum. This study examines the role of epigenetic changes, including DNA methylation and histone modification, in silencing of inhibin α gene expression. Bisulfite sequencing reveals that methylation of the inhibin α proximal promoter is low in preovulatory and ovulatory follicles but is elevated in the corpus luteum. Increased methylation during luteinization is observed within the cAMP response element in the promoter, and EMSA demonstrate that methylation of this site inhibits cAMP response element binding protein binding in vitro. Chromatin immunoprecipitation reveals that repressive histone marks H3K9 and H3K27 trimethylation are increased on the inhibin α promoter in primary luteal cells, whereas the activation mark H3K4 trimethylation is decreased. The changes in histone modification precede the alterations in DNA methylation, suggesting that they facilitate the recruitment of DNA methyltransferases. We show that the DNA methyltransferase DNMT3a is present in the ovary and in luteal cells when the inhibin α promoter becomes methylated and observe recruitment of DNMT3a to the inhibin promoter during luteinization.

Mutations in inhibin and activin genes associated with human disease

Inhibins and activins are members of the transforming growth factor (TGFβ) superfamily, that includes the TGFβs, inhibins and activins, bone morphogenetic proteins (BMPs) and growth and differentiation factors (GDFs). The family members are expressed throughout the human body, and are involved in the regulation of a range of important functions. The precise regulation of the TGFβ pathways is critical, and mutations of individual molecules or even minor alterations of signalling will have a significant affect on function, that may lead to development of disease or predisposition to the development of disease. The inhibins and activins regulate aspects of the male and female reproductive system, therefore, it is not surprising that most of the diseases associated with abnormalities of the inhibin and activin genes are focused on reproductive disorders and reproductive cancers. In this review, I highlight the role of genetic variants in the development of conditions such as premature ovarian failure, pre-eclampsia, and various reproductive cancers. Given the recent advances in human genetic research, such as genome wide association studies and next generation sequencing, it is likely that inhibins and activins will be shown to play more important roles in a range of human genetic diseases in the future.

Luteinizing hormone regulates inhibin-α subunit expression through multiple signaling pathways involving steroidogenic factor-1 and beta-catenin in the macaque corpus luteum

We employed different experimental model systems to define the role of GATA4, beta-catenin, and steroidogenic factor (SF-1) transcriptional factors in the regulation of monkey luteal inhibin secretion. Reverse transcription polymerase chain reactions and western blotting analyses show high expression of inhibin-α, GATA4, and beta-catenin in corpus luteum (CL) of the mid-luteal phase. Gonadotropin-releasing hormone receptor antagonist-induced luteolysis model suggested the significance of luteinizing hormone (LH) in regulating these transcriptional factors. Inducible cyclic AMP early repressor mRNA expression was detected in the CL and no change was observed in different stages of CL. Following amino acid sequence analysis, interaction between SF-1 and beta-catenin in mid-stage CL was verified by reciprocal co-immunoprecipitation experiments coupled to immunoblot analysis. Electrophoretic mobility shift analysis support the role of SF-1 in regulating luteal inhibin-α expression. Our results suggest a possible multiple crosstalk of Wnt, cAMP, and SF-1 in the regulation of luteal inhibin secretion.

Action mechanism of inhibin α-subunit on the development of Sertoli cells and first wave of spermatogenesis in mice

Inhibin is an important marker of Sertoli cell (SC) activity in animals with impaired spermatogenesis. However, the precise relationship between inhibin and SC activity is unknown. To investigate this relationship, we partially silenced both the transcription and translation of the gene for the α-subunit of inhibin, Inha, using recombinant pshRNA vectors developed with RNAi-Ready pSIREN-RetroQ-ZsGreen Vector (Clontech Laboratories, Mountain View, Calif). We found that Inha silencing suppresses the cell-cycle regulators Cyclin D1 and Cyclin E and up-regulates the cell-cycle inhibitor P21 (as detected by Western blot analysis), thereby increasing the number of SCs in the G1 phase of the cell cycle and decreasing the amount in the S-phase of the cell cycle (as detected by flow cytometry). Inha silencing also suppressed Pdgfa, Igf1, and Kitl mRNA levels and up-regulated Tgfbrs, Inhba, Inhbb, Cyp11a1, Dhh, and Tjp1 mRNA levels (as indicated by real-time polymerase chain reaction [PCR] analysis). These findings indicate that Inha has the potential to influence the availability of the ligand inhibin and its antagonist activin in the SC in an autocrine manner and inhibit the progression of SC from G1 to S. It may also participate in the development of the blood–testis barrier, Leydig cells, and spermatogenesis through its effect on Dhh, Tjp1, Kitl, and Pdgfa. Real-time PCR and Western blot analyses of Inha, Inhba, and Inhbb mRNA and Inha levels over time show that Inha plays an important role in the formation of round spermatid during the first wave of spermatogenesis in mice.