Mutational analysis of the mature peptide region of inhibin genes in Indian women with ovarian failure

TGF-β signaling in health and disease

The TGF-β regulatory system plays crucial roles in the preservation of organismal integrity. TGF-β signaling controls metazoan embryo development, tissue homeostasis, and injury repair through coordinated effects on cell proliferation, phenotypic plasticity, migration, metabolic adaptation, and immune surveillance of multiple cell types in shared ecosystems. Defects of TGF-β signaling, particularly in epithelial cells, tissue fibroblasts, and immune cells, disrupt immune tolerance, promote inflammation, underlie the pathogenesis of fibrosis and cancer, and contribute to the resistance of these diseases to treatment. Here, we review how TGF-β coordinates multicellular response programs in health and disease and how this knowledge can be leveraged to develop treatments for diseases of the TGF-β system.

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.

Identification of Novel Nucleotide Changes in INHBB Gene by Mutation Screening in Females with Ovarian Dysgenesis: A Case Report

Background:

Inhibin and activin regulate the follicle stimulating hormone level by their antagonistic actions and thus have been considered as strong candidate genes in the etiology of ovarian dysgenesis. In the present study, two cases of primary amenorrhea with poorly developed secondary sexual characteristics were reported. The purpose of the study was to identify mutations in candidate gene.

Case Presentation:

In this paper, clinical, genetic, biochemical, and molecular findings in female patients with primary amenorrhea were reported. Whole blood culture and G-banding for karyotyping, sequencing, and in silico analysis were performed following the standard protocol. Both cases were cytogenetically characterized as normal females with 46,XX, chromosome constitution. Hormonal assay revealed high level of follicle stimulating hormone and luteinizing hormone. DNA sequence analysis of inhibin identified two novel heterozygous missense mutations of c.975T>A and c.1156G>A which were translated into p.I310N and p.D386N, respectively. These identified positions were highly conserved across species during evolution. In silico prediction tools, intramolecular hydrogen bonding pattern and hydrophobicity analysis, revealed deleterious effect of p.I310N and neutral effect of p.D386N mutation.

Conclusion:

Our observation suggested that identified novel mutation in the first case might be the reason for ovarian dysgenesis and provides additional support to the previously reported genotype-phenotype correlations.

Genetics of ovarian insufficiency and defects of folliculogenesis

Primary ovarian insufficiency (POI) is determined by exhaustion of follicles in the ovaries, which leads to infertility before the age of 40 years. It is characterized by a strong familial and heterogeneous genetic background. Therefore, we will mainly discuss the genetic basis of POI in this review. We identified 107 genes related to POI etiology in mammals described by several independent groups. Thirty-four of these genes (AARS2, AIRE, ANTXR1, ATM, BMPR1B, CLPP, CYP17A1, CYP19A1, DCAF17, EIF2B, ERAL1, FANCA, FANCC, FMR1, FOXL2, GALT, GNAS, HARS2, HSD17B4, LARS2, LMNA, MGME1, NBN, PMM2, POLG, PREPL, RCBTB1, RECQL2/3/4, STAR, TWNK, and XRCC4/9) have been linked to syndromic POI and are mainly implicated in metabolism function and meiosis/DNA repair. In addition, the majority of genes associated with nonsyndromic POI, widely expanded by high-throughput techniques over the last decade, have been implicated in ovarian development and meiosis/DNA repair pathways (ATG7, ATG9, ANKRD31, BMP8B, BMP15, BMPR1A, BMPR1B, BMPR2, BNC1, BRCA2, CPEB1, C14ORF39, DAZL, DIAPH2, DMC1, ERCC6, FANCL, FANCM, FIGLA, FSHR, GATA4, GDF9, GJA4, HELQ, HSF2BP, HFM1, INSL3, LHCGR, LHX8, MCM8, MCM9, MEIOB, MSH4, MSH5, NANOS3, NOBOX, NOTCH2, NR5A1, NUP107, PGRMC1, POLR3H, PRDM1, PRDM9, PSMC3IP, SOHLH1, SOHLH2, SPIDR, STAG3, SYCE1, TP63, UBR2, WDR62, and XRCC2), whereas a few are related to metabolic functions (EIF4ENIF1, KHDRBS1, MRPS22, POLR2C). Some genes, such as STRA8, FOXO3A, KIT, KITL, WNT4, and FANCE, have been shown to cause ovarian insufficiency in rodents, but mutations in these genes have yet to be elucidated in women affected by POI. Lastly, some genes have been rarely implicated in its etiology (AMH, AMHR2, ERRC2, ESR1, INHA, LMN4, POF1B, POU5F1, REC8, SMC1B). Considering the heterogeneous genetic and familial background of this disorder, we hope that an overview of literature data would reinforce that genetic screening of those patients is worthwhile and helpful for better genetic counseling and patient management.

Transcriptome Analyses Identify Potential Key microRNAs and Their Target Genes Contributing to Ovarian Reserve

Female endocrinological symptoms, such as premature ovarian inefficiency (POI) are caused by diminished ovarian reserve and chemotherapy. The etiology of POI remains unknown, but this can lead to infertility. This has accelerated the search for master regulator genes or other molecules that contribute as enhancers or silencers. The impact of regulatory microRNAs (miRNAs) on POI has gained attention; however, their regulatory function in this condition is not well known. RNA sequencing was performed at four stages, 2-(2 W), 6-(6 W), 15-(15 W), and 20-(20 W) weeks, on ovarian tissue samples and 5058 differentially expressed genes (DEGs) were identified. Gene expression and enrichment were analyzed based on the gene ontology and KEGG databases, and their association with other proteins was assessed using the STRING database. Gene set enrichment analysis was performed to identify the key target genes. The DEGs were most highly enriched in 6 W and 15 W groups. Figla, GDF9, Nobox, and Pou51 were significantly in-creased at 2 W compared with levels at 6 W and 20 W, whereas the expression of Foxo1, Inha, and Taf4b was significantly de-creased at 20 W. Ccnd2 and Igf1 expression was maintained at similar levels in each stage. In total, 27 genes were upregulated and 26 genes interacted with miRNAs; moreover, stage-specific upregulated and downregulated interactions were demonstrated. Increased and decreased miRNAs were identified at each stage in the ovaries. The constitutively expressed genes, Ccnd2 and Igf1, were identified as the major targets of many miRNAs (p < 0.05), and Fshr and Foxo3 interacted with miRNAs, namely mmu-miR-670-3p and mmu-miR-153-3p. miR-26a-5p interacted with Piwil2, and its target genes were downregulated in the 20 W mouse ovary. In this study, we aimed to identify key miRNAs and their target genes encompassing the reproductive span of mouse ovaries using mRNA and miRNA sequencing. These results indicated that gene sets are regulated in the reproductive stage-specific manner via interaction with miRNAs. Furthermore, consistent expression of Ccnd2 and Igf1 is considered crucial for the ovarian reserve and is regulated by many interactive miRNAs.

Premature Ovarian Insufficiency: Past, Present, and Future

Premature ovarian insufficiency (POI) is the loss of normal ovarian function before the age of 40 years, a condition that affects approximately 1% of women under 40 years old and 0.1% of women under 30 years old. It is biochemically characterized by amenorrhea with hypoestrogenic and hypergonadotropic conditions, in some cases, causing loss of fertility. Heterogeneity of POI is registered by genetic and non-genetic causes, such as autoimmunity, environmental toxins, and chemicals. The identification of possible causative genes and selection of candidate genes for POI confirmation remain to be elucidated in cases of idiopathic POI. This review discusses the current understanding and future prospects of heterogeneous POI. We focus on the genetic basis of POI and the recent studies on non-coding RNA in POI pathogenesis as well as on animal models of POI pathogenesis, which help unravel POI mechanisms and potential targets. Despite the latest discoveries, the crosstalk among gene regulatory networks and the possible therapies targeting the same needs to explore in near future.

The Effects of Inhibin B in the Chemotherapy Drug-Induced Premature Ovarian Insufficiency Mice and hPMSCs Treatment

Human placenta mesenchymal stem cells (hPMSCs), have been extensively investigated on the treatment of many diseases. This study was to explore the effects of hPMSCs treatment on the chemotherapy drug-induced premature ovarian insufficiency (POI) mice. Cyclophosphamide (120 mg/kg) and busulfan (30 mg/kg) or cyclophosphamide (70 mg/kg) induced POI mice were used and hPMSCs were injected through tail vein. The hormone levels of serum, morphological changes, the expression and quantitative analysis of inhibin B (INHBB) and FSHR protein, and apoptosis of granulosa cells in ovary were detected. The granulosa cells (GCs) were detected from ovaries of mice and the different concentration of cyclophosphamide on GCs were detected by MTT assay. The apoptosis of GCs was detected by FITC Annexin V Apoptosis Detection Kit. The significant increase in FSH and decrease in E₂ and INHBB were observed. Expression of human nuclei was observed in the stroma of ovaries. INHBB and FSHR levels of ovaries were reduced in the POI mice. Following hPMSCs treatment, the amounts of INHBB and FSHR significantly increased close to normal levels. The granulosa cells apoptosis increased in the POI ovaries but decreased after hPMSCs treatment. Moreover, cyclophosphamide has no effect on the GCs and no statistic difference was measured in vitro. The effects of hPMSCs treatment reduce the apoptosis of granulosa cells and restore the ovarian reserve capacity in chemotherapeutic drug-induced POI mice. The data help to further explore new potential clinical therapeutic approach for POI patients.

Variations in the inhibin gene in Kashmiri women with primary ovarian insufficiency

Inhibin is a glycoprotein produced by granulosa cells and its main function is the negative feedback control of follicle stimulating hormone (FSH) which has an important role in folliculogenesis. Mutation in the INHα gene leading to decreased bioactive inhibin has been associated with primary ovarian insufficiency (POI). The aim of this study was to investigate the role of variations in the INHα gene in increasing the susceptibility to POI in Kashmiri women. INHα c.769G > A mutation was analysed in 100 POI cases and 100 controls using PCR-RFLP and agarose gel electrophoresis. The INHα c.769G > A mutation was found in 10% of POI cases with 8% having heterozygous mutation and 2% having a homozygous mutation. The frequency of mutation in healthy controls was zero. Statistically, a very significant association was found between INHα c.769G > A mutation and the occurrence of POI (p = 0.0015). Moreover, the mutation was also significantly associated with high levels of FSH in POI patients (p < 0.0001). Given the significant association of INHα c.769G > A mutation with the increased FSH levels and POI in Kashmiri population, we suggest this mutation can be used to identify POI variants for screening of women susceptible to POI before the disease onset and can further facilitate putative therapy for such patients.

How polymorphic markers contribute to genetic diseases in different populations? The study of inhibin A for premature ovarian insufficiency

OBJECTIVE

To verify the incidence of the G679A mutation in exon 2 of the gene inhibin alpha (INHA), in women with secondary amenorrhea and diagnosis of premature ovarian insufficiency, and in controls.

METHODS

A 5mL sample of peripheral blood was collected from all study participants in an EDTA tube and was used for DNA extraction. For the patient group, 5mL of blood were also collected in a tube containing heparin for karyotype, and 5mL were collected in a dry tube for follicle stimulant hormone dosage. All patient and control samples were initially submitted to analysis of the G679A variant in exon 2 of the INHA gene by PCR-RFLP technique. Samples from patients with premature ovarian insufficiency after PCR-RFLP were submitted to Sanger sequencing of the encoding exons 2 and 3. Sequencing was performed on ABI 3500 GeneticAnalyzer equipment and the results were evaluated by SeqA and Variant Reporter software.

RESULTS

Samples of 70 women with premature ovarian insufficiency and 97 fertile controls were evaluated. The G769A variant was found in only one patient in the Premature Ovarian Insufficiency Group and in no control, and it appears to be rare in Brazilian patients with premature ovarian insufficiency. This polymorphism was previously associated to premature ovarian insufficiency in several populations worldwide.

CONCLUSION

There is genetic heterogeneity regarding the INHA gene in different populations, and among the causes of premature ovarian insufficiency.

Primary ovarian insufficiency with t(5;13): a case report and literature review on disrupted genes

OBJECTIVES

To report a woman with primary ovarian insufficiency (POI) with reciprocal translocation between chromosomes 5 and 13.

METHODS

Chromosomal analysis (G-banding) of a 39-year-old woman with elevated gonadotropin levels and secondary amenorrhea and review of the literature with a special focus on disrupted genes at the reported breakpoints.

RESULTS

A reciprocal translocation between the long arms of chromosomes 5 and 13 was identified in the patient (46,XX,t(5;13)(q13;q14)). Investigation of the breakpoints revealed that the 13q14.1 region encompasses FOXO1 (forkhead box 1) gene, which has an important role in granulosa cell function and follicle maturation.

CONCLUSIONS

Autosomal translocations are rare in women with POI. We have reported the first case of a de novo reciprocal translocation involving chromosomes 5 and 13 in a POI patient. As one of the breakpoints encompasses the FOXO1 gene, it seems that disruption of this gene can be the cause of POI in this patient. This provides further evidence on the role of autosomal translocations in disrupting POI-associated genes. Therefore, concentrating on the genes at the breakpoints will be helpful to delineate the new biological pathways or genes involved in POI pathogenesis.

Genetics of the ovarian reserve

Primordial follicles or non-growing follicles (NGFs) are the functional unit of reproduction, each comprising a single germ cell surrounded by supporting somatic cells. NGFs constitute the ovarian reserve (OR), prerequisite for germ cell ovulation and the continuation of the species. The dynamics of the reserve is determined by the number of NGFs formed and their complex subsequent fates. During the reproductive lifespan, the OR progressively diminishes due to follicle atresia as well as recruitment, maturation, and ovulation. The depletion of the OR is the major determining driver of menopause, which ensues when the number of primordial follicles falls below a threshold of ∼1,000. Therefore, genes and processes involved in follicle dynamics are particularly important to understand the process of menopause, both in the typical reproductive lifespan and in conditions like primary ovarian insufficiency, defined as menopause before age 40. Genes and their variants that affect the timing of menopause thereby provide candidates for diagnosis of and intervention in problems of reproductive lifespan. We review the current knowledge of processes and genes involved in the development of the OR and in the dynamics of ovarian follicles.

The genetics of premature ovarian failure: current perspectives

Premature ovarian failure (POF) is a common cause of infertility in women, characterized by amenorrhea, hypoestrogenism, and elevated gonadotropin levels in women under the age of 40. Many genes have been identified over the past few years that contribute to the development of POF. However, few genes have been identified that can explain a substantial proportion of cases of POF. The unbiased approaches of genome-wide association studies and next-generation sequencing technologies have identified several novel genes implicated in POF. As only a small proportion of genes influencing idiopathic POF have been identified thus far, it remains to be determined how many genes and molecular pathways may influence idiopathic POF development. However, owing to POF’s diverse etiology and genetic heterogeneity, we expect to see the contribution of several new and novel molecular pathways that will greatly enhance our understanding of the regulation of ovarian function. Future genetic studies in large cohorts of well-defined, unrelated, idiopathic POF patients will provide a great opportunity to identify the missing heritability of idiopathic POF. The identification of several causative genes may allow for early detection and would provide better opportunity for early intervention, and furthermore, the identification of specific gene defects will help direct potential targets for future treatment.

Genetics of primary ovarian insufficiency: new developments and opportunities

BACKGROUND

Primary ovarian insufficiency (POI) is characterized by marked heterogeneity, but with a significant genetic contribution. Identifying exact causative genes has been challenging, with many discoveries not replicated. It is timely to take stock of the field, outlining the progress made, framing the controversies and anticipating future directions in elucidating the genetics of POI.

METHODS

A search for original articles published up to May 2015 was performed using PubMed and Google Scholar, identifying studies on the genetic etiology of POI. Studies were included if chromosomal analysis, candidate gene screening and a genome-wide study were conducted. Articles identified were restricted to English language full-text papers.

RESULTS

Chromosomal abnormalities have long been recognized as a frequent cause of POI, with a currently estimated prevalence of 10-13%. Using the traditional karyotype methodology, monosomy X, mosaicism, X chromosome deletions and rearrangements, X-autosome translocations, and isochromosomes have been detected. Based on candidate gene studies, single gene perturbations unequivocally having a deleterious effect in at least one population include Bone morphogenetic protein 15 (BMP15), Progesterone receptor membrane component 1 (PGRMC1), and Fragile X mental retardation 1 (FMR1) premutation on the X chromosome; Growth differentiation factor 9 (GDF9), Folliculogenesis specific bHLH transcription factor (FIGLA), Newborn ovary homeobox gene (NOBOX), Nuclear receptor subfamily 5, group A, member 1 (NR5A1) and Nanos homolog 3 (NANOS3) seem likely as well, but mostly being found in no more than 1-2% of a single population studied. Whole genome approaches have utilized genome-wide association studies (GWAS) to reveal loci not predicted on the basis of a candidate gene, but it remains difficult to locate causative genes and susceptible loci were not always replicated. Cytogenomic methods (array CGH) have identified other regions of interest but studies have not shown consistent results, the resolution of arrays has varied and replication is uncommon. Whole-exome sequencing in non-syndromic POI kindreds has only recently begun, revealing mutations in the Stromal antigen 3 (STAG3), Synaptonemal complex central element 1 (SYCE1), minichromosome maintenance complex component 8 and 9 (MCM8, MCM9) and ATP-dependent DNA helicase homolog (HFM1) genes. Given the slow progress in candidate-gene analysis and relatively small sample sizes available for GWAS, family-based whole exome and whole genome sequencing appear to be the most promising approaches for detecting potential genes responsible for POI.

CONCLUSION

Taken together, the cytogenetic, cytogenomic (array CGH) and exome sequencing approaches have revealed a genetic causation in ∼20-25% of POI cases. Uncovering the remainder of the causative genes will be facilitated not only by whole genome approaches involving larger cohorts in multiple populations but also incorporating environmental exposures and exploring signaling pathways in intragenic and intergenic regions that point to perturbations in regulatory genes and networks.

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.

Single nucleotide polymorphisms in premature ovarian failure-associated genes in a Chinese Hui population

Premature ovarian failure (POF) is an ovarian defect characterized by the premature depletion of ovarian follicles in individuals <40 years old, and is a major cause of infertility in females. Genetic factors are considered to be responsible for the development of POF, however, the exact pathogenesis remains to be elucidated in the majority of cases. In the present study, the single nucleotide polymorphisms (SNPs) of growth differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), inhibin βB (INHBB) and follicle stimulating hormone receptor (FSHR) genes were investigated, and their association with POF in a Chinese Hui population of the Ningxia Hui Autonomous Region in western China was evaluated. Peripheral blood samples were collected from 63 patients diagnosed with POF (POF group) and 58 normal control individuals (control group), from which the genomic DNA was isolated. The GDF9, BMP15, INHBB and FSHR genes were amplified using polymerase chain reaction assays, and their SNPs were determined by sequencing. In the four SNPs identified across the GDF9 loci, D57Y (169G>T), rs1049127 (546G>A), rs254286 (447C>T) and rs254285 (969C>G), the frequencies of the 546G>A genotype and allele A were significantly higher in the POF group, compared with the normal control group (34.92, vs. 6.90%; P<0.05 and 19.05, vs. 3.23%; P<0.05, repsectively), while no significant differences were observed in the occur rence of the c.447C>T and c.969C>G mutations between the two groups (60.32, vs. 50% and 50.79, vs. 55.17%, repsectively). The c.169G>T mutation within the GDF9 gene was only detected in two patients with POF, and the mutation did not occur in the normal control group. A total of three SNPs were detected within the BMP15 gene, including rs3810682 (−9C>G), rs79377927 (788_789insTCT) and rs17003221 (852C>T), and no significant differences were observed in the frequencies of the 9C>G and 852C>T genotypes between the POF and control groups (7.94, vs. 6.90% and 4.76, vs. 3.45%, respectively). The 788_789insTCT genotype was detected in only two patients with POF. A novel mutation, c.1095C>A, was identified in exon 2 of the INHBB gene, however, no significant difference was found in the occurrence of the mutation between the two groups (30.16, vs. 22.41%; P>0.05). The rs6165 (919G>A) and rs6166 (2039G>A) SNPs were detected in exon 10 of the FSHR gene; however, no significant difference was observed in the genotype frequencies between the two groups (92.06, vs. 91.38% and 96.83, vs. 93.10%, respecrively). These results demonstrated that GDF9 c.169G>T (D57Y), c.546G>A (rs1049127), and BMP15 rs79377927 (788_789insTCT) were associated with POF in the Chinese Hui population.

Genetics of female infertility due to anomalies of the ovary and mullerian ducts

Genetic factors are pivotal in reproductive development and subsequent reproductive processes. If disturbed, infertility can occur. In the female, genetic factors affecting the ovary and the uterus are not uncommon causes of infertility. Terminal deletions on the X long arm and X short arm and X chromosomal mosaicism have long been accepted as causes of premature ovarian failure (POF). Responsible genes on the X have not yet elucidated. Attractive candidate genes for POF also exist on autosomes, and in over a dozen genes molecular perturbations are documented in non-syndromic POF. The most common single-gene cause of POF is premutation carriers for FMR1 (fragile X syndrome). As other candidate genes and additional ethnic groups are interrogated, the proportion of POF cases due to single-gene mutation will increase. Among uterine anomalies, incomplete mullerian fusion is most common. Increased recurrence risks for first-degree relatives confirm a role for genetic factors; interrogation of candidate genes is under way.

Inhibin at 90: from discovery to clinical application, a historical review

When it was initially discovered in 1923, inhibin was characterized as a hypophysiotropic hormone that acts on pituitary cells to regulate pituitary hormone secretion. Ninety years later, what we know about inhibin stretches far beyond its well-established capacity to inhibit activin signaling and suppress pituitary FSH production. Inhibin is one of the major reproductive hormones involved in the regulation of folliculogenesis and steroidogenesis. Although the physiological role of inhibin as an activin antagonist in other organ systems is not as well defined as it is in the pituitary-gonadal axis, inhibin also modulates biological processes in other organs through paracrine, autocrine, and/or endocrine mechanisms. Inhibin and components of its signaling pathway are expressed in many organs. Diagnostically, inhibin is used for prenatal screening of Down syndrome as part of the quadruple test and as a biochemical marker in the assessment of ovarian reserve. In this review, we provide a comprehensive summary of our current understanding of the biological role of inhibin, its relationship with activin, its signaling mechanisms, and its potential value as a diagnostic marker for reproductive function and pregnancy-associated conditions.

Association of inhibin α gene promoter polymorphisms with risk of idiopathic primary ovarian insufficiency in Korean women

OBJECTIVE

The aim of this study was to investigate whether two polymorphisms in the promoter region of inhibin alpha (INHA) are associated with risk of idiopathic primary ovarian insufficiency (POI) in Korean women, which is a controversial topic.

STUDY DESIGN

We genotyped the INHA polymorphisms c.-16C>T (rs35118453) and c.-124A>G (rs11893842) of 136 POI patients and 225 controls in Korean women by polymerase chain reaction and restriction fragment length polymorphism analysis. We then compared differences in genotype and allele frequencies (AF) of the polymorphisms between the two groups to determine odds ratios (OR) and 95% confidence intervals (CI) as measures of the strength of association between genotype and POI.

RESULTS

There were no significant differences in genotype or AF of the polymorphisms between the POI patients and controls. Haplotype analysis revealed that the T-G haplotype of the two variant alleles was more frequent in POI patients than in the controls (OR=1.630, 95% CI=1.081-2.457). Combination genotype analysis showed that the CT+TT/GG genotype frequency was higher in POI patients than in the controls (OR=2.414, 95% CI=1.190-4.895).

CONCLUSIONS

We provide evidence to suggest that when the two variant alleles are combined, the c.-16C>T and c.-124A>G polymorphisms are associated with increased POI risk in Korean women. We postulate that interactions between the INHA polymorphisms may affect POI risk.

Differentiation of rat iPS cells and ES cells into granulosa cell-like cells in vitro

Premature ovarian failure (POF) is an ovarian defect characterized by the premature depletion of ovarian follicles before 40 years of age, representing one major cause of female infertility. Stem cells provide the possibility of a potential treatment for POF. In this study, rat embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) were co-cultured with granulosa cells (GCs) to differentiate to GC-like cells. The level of estradiol (E2) analyzed by radioimmunoassay showed that the E2 concentration of the culture supernatant of co-cultured rat iPSCs and ESCs increased in a time-dependent manner, compared with the GCs group that has an opposite trend. The expression of follicle-stimulating hormone receptor (FSHR) was confirmed by immunostaining. These results indicated that rat iPSCs and ESCs were effectively induced to GC-like cells through indirect cell-to-cell contact. Real-time polymerase chain reaction was performed to analyze the expression level of marker genes in POF, including BMP15, FMR1, FSHR, INHA, AMH, NOBOX, FOXO3, EIF2B, FIGLA, and GDF9. The BMP15, FSHR, INHA, AMH, NOBOX, and GDF9 genes were significantly up-regulated in iPSCs and ESCs co-cultured with GCs in comparison with cells that were not co-cultured. Thus, here we demonstrated an available method to differentiate rat iPSCs and ESCs into GC-like cells in vitro for the possible cell therapy of POF.

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.

The ovarian reserve in mammals: a functional and evolutionary perspective

The constitution and the control of the ovarian reserve is of importance in mammals and women. In particular, the number of primordial follicles at puberty is positively correlated with the number of growing follicles and their response to gonadotropin treatments. The size of this ovarian reserve depends on genes involved in germ cell proliferation and differentiation, sexual differentiation, meiosis, germ cell degeneration, formation of primordial follicles, and on a potential mechanism of self-renewal of germ stem cells. In this review, we present the state of the art of the knowledge of genes and factors involved in all these processes. We first focus on the almost 70 genes identified mainly by mouse invalidation models, then we discuss the most plausible hypothesis concerning the possibility of the existence of germ cell self-renewal by neo-oogenesis in animal species and human, with a special interest for the role of corresponding genes in evolutionary distinct model species. All of the genes pointed out here are candidates susceptible to explain fertility defects such as the premature ovarian failure in human.

Inhibin α-subunit N terminus interacts with activin type IB receptor to disrupt activin signaling

Inhibin is a heterodimeric peptide hormone produced in the ovary that antagonizes activin signaling and FSH synthesis in the pituitary. The inhibin β-subunit interacts with the activin type II receptor (ActRII) to functionally antagonize activin. The inhibin α-subunit mature domain (N terminus) arose relatively early during the evolution of the hormone, and inhibin function is decreased by an antibody directed against the α-subunit N-terminal extension region or by deletion of the N-terminal region. We hypothesized that the α-subunit N-terminal extension region interacts with the activin type I receptor (ALK4) to antagonize activin signaling in the pituitary. Human or chicken free α-subunit inhibited activin signaling in a pituitary gonadotrope-derived cell line (LβT2) in a dose-dependent manner, whereas an N-terminal extension deletion mutant did not. An α-subunit N-terminal peptide, but not a control peptide, was able to inhibit activin A signaling and decrease activin-stimulated FSH synthesis. Biotinylated inhibin A, but not activin A, bound ALK4. Soluble ALK4-ECD bioneutralized human free α-subunit in LβT2 cells, but did not affect activin A function. Competitive binding ELISAs with N-terminal mutants and an N-terminal region peptide confirmed that this region is critical for direct interaction of the α-subunit with ALK4. These data expand our understanding of how endocrine inhibin achieves potent antagonism of local, constitutive activin action in the pituitary, through a combined mechanism of competitive binding of both ActRII and ALK4 by each subunit of the inhibin heterodimer, in conjunction with the co-receptor betaglycan, to block activin receptor-ligand binding, complex assembly, and downstream signaling.

Haplotype and mutation analysis of the TGFBR3 gene in Chinese women with idiopathic premature ovarian failure

This study screened the TGFBR3 mutations in Chinese patients with idiopathic premature ovarian failure (POF) to gain a better understanding the genetic aetiology of POF. One hundred twelve Chinese patients with idiopathic POF and 110 women from normal controls were examined. The coding region and respective flanking intronic regions of the TGFBR3 gene were amplified by the PCR, and the DNA fragments were directly sequenced. Twenty-eight sequence variants, including 12 novel variants, were identified. These novel variants included three missense mutations, two synonymous mutations, and seven mutations in the intronic region. Three novel exonic missense variants were p.E458G, p.P824L, and p.I836V. The c.566-216G>A, c.566-71C>T, c.2022T>C, c.2502A>G, and c.2568G>A variants represented significantly different genotype distribution between POF cases and the controls. The binary logistic regression analysis of c.566-216G>A, c.566-71C>T, and c.2502A>G variants were significantly associated with the POF patients and the ATTAG haplotype was most significantly over-represented as compared with controls (P = 0.00121). The ATTGG and GCTGG haplotypes were significantly higher in controls than in patients (P = 0.00113 and 0.00055, respectively). Other less frequent haplotypes, such as GCCGA, was only present in the patients (P = 0.00066). GTTGG was only present in the controls (P = 0.00001). Significant diversity of genotype distribution and haplotype analysis suggested that TGFBR3 mutations may be responsible for the genetic aetiology of idiopathic POF in Chinese patients.

Relationship between inhibin-α gene polymorphisms and premature ovarian failure in Korean women

OBJECTIVE

The aim of this study was to determine the relationship between inhibin-α (INHα) gene polymorphisms and the prevalence of premature ovarian failure (POF) in Korean women.

METHODS

The INHα -124A/G, -16C/T, 679G/A, and 769G/A polymorphisms were analyzed in 52 women with POF and 55 normal healthy women using polymerase chain reaction-restriction enzyme fragment length polymorphism analysis.

RESULTS

The 679G/A and 769G/A polymorphisms were not observed. The frequencies of the C allele of the INHα -16C/T polymorphism and the G allele of the INHα -124A/G polymorphism were significantly lower in the women with POF than in the normal control women. The frequencies of the CG haplotype allele of these INHα -16C/T and -124A/G gene polymorphisms were also significantly lower in the women with POF than in the control women.

CONCLUSIONS

The INHα -16C/T and -124A/G polymorphisms are genetic factors associated with the prevalence of POF in Korean women.

Contemporary genetic technologies and female reproduction

BACKGROUND

The Fifth Evian Annual Reproduction (EVAR) Workshop Meeting discussed knowledge regarding contemporary genetics in female reproduction.

METHODS

Specialist reproductive medicine clinicians and geneticists delivered presentations based on published literature and current research. The content of this report is based on the expert presentations and subsequent group discussions that took place during this Workshop.

RESULTS

Numerous ovarian genes with a role in infertility have been identified. Future challenges for genetic screening of patients, such as those with polycystic ovary syndrome, primary ovarian insufficiency or endometriosis, include the identification of high-throughput strategies and how to apply these findings to infertile patients. The identification of high-quality embryos in IVF using objective technologies remains a high priority in order to facilitate single-embryo transfer. Gene expression profiling of cumulus cells surrounding the oocyte, and proteomic and metabolomic approaches in embryo culture media may significantly improve non-invasive embryo quality assessment.

CONCLUSIONS

The way forward in advancing the knowledge of genes involved in reproduction was considered to be through genome-wide association studies involving large numbers of patients. Establishing international collaboration is required to enable the application of such technologies in sufficient numbers of patients.

Genetic defects of ovarian TGF-β-like factors and premature ovarian failure

Premature ovarian failure (POF) is an ovarian defect characterized by the premature depletion of ovarian follicles; POF affects approximately 1-2% of women under the age of 40 yr, thus representing one major cause of female infertility. POF relevance is continuously growing because women tend to conceive always more frequently beyond 30 yr. Frequently, POF is the end-stage of an occult process [primary ovarian insufficiency (POI)]. POI is a heterogeneous disease caused by a variety of mechanisms. Though the underlying cause remains unexplained in the majority of cases, several data indicate that POI has a strong genetic component. These data include the existence of several causal genetic defects in human, experimental, and natural models, as well as the frequent familiarity. The candidate genes are numerous, but POF remains unexplained in most of the cases. Several recent evidences have driven the attention of researchers on the possible involvement of various elements belonging to the transforming growth factor β family, which includes bone morphogenetic proteins, growth/differentiation factors, and inhibins. These peptides are produced by either the oocyte or granulosa cells to constitute a complex paracrine network within the ovarian follicle. Here, we review the studies reporting the genetic alterations of these factors in human and animal defects of ovarian folliculogenesis which support the fundamental roles played by these signals in ovarian morphogenesis and function.

New targets for old hormones: inhibins clinical role revisited

Inhibins are gonadal peptide hormones belonging to the transforming growth factor-β (TGF-β) superfamily that regulate the pituitary follicle stimulating hormone (FSH) secretion by negative feedback mechanisms. It is evident that the understanding of inhibins function in the hypothalamic-pituitary-gonadal axis will provide insights into physiology and pathology of the gonadal function. In recent years, a great deal of attention has been focussed on clinical relevance of measuring circulating inhibins in normal and disease state. The past few years also have witnessed the emergence and discovery of extra pituitary action of inhibins that might provide further insights into the underlying diseases like cancer especially in the reproductive axis and various other new endocrine target organs. In this review after systematic analysis of literature, we discuss briefly the known and recent advances in function of these hormones highlighting also its structure, production and mechanisms of signal transduction. Also this review discusses about the physiological relevance of inhibin association in the normal function to the development of reproductive cancers. Finally, we describe evidence from various emerging studies that inhibins make an important contribution to other physiological functions apart from reproduction which reveals new endocrine target organs of inhibins. The emerging view is inhibin participates in multiple ways to regulate the function in different cell types and still complete repertoire of its actions is under investigation.

Chromosomal abnormalities in women with premature ovarian failure

Premature ovarian failure is a complex disorder that results in the early loss of ovarian function; however this disease must be separated from early menopause because these patients can sporadically ovulate and in literature are described pregnancies. The aetiology and the patho-physiology of premature ovarian failure are still matter of debate, but is commonly accepted that genetic factors play an important role. This review is aimed to present an overview of known inherited factor implied in the pathogenesis of this disorder to help physician in the counselling of affected pregnant women.

Genes governing premature ovarian failure

Premature ovarian failure (POF) is unexplained amenorrhoea (>6 months), increased FSH (>20 IU/l) and LH occurring before 40 years. Several genes are reported as having significance in POF, including genes governing regulation of the hypothalamic-pituitary-ovarian axis, but their role in ovarian physiology is not known. Deletions or translocations in Xq arm have been found to be associated with POF, assuming presence of ovarian-related genes but ovary-related function of these genes is unclear. Several researchers have suggested specific loci on Xq critical region, POF1 and POF2 and genes DIA, FMR1 and FMR2. The understanding of ovarian physiology, its regulation and genes involved is important to explain the causes of POF. Some genes coordinate development of germ cell to primordial stage, e.g. GDF9, BMP15 and NGF, while others regulate development of further stages, such as FSH and LH. Mutation in these genes may lead to female infertility and are likely to be candidate genes for POF. Recently, association between blepharophimosis-ptosis-epicanthus inversus syndrome type 1 and POF has emerged as a possibility. Galactosaemia is also shown to be important in POF due to toxic effects of accumulated galactose or downstream products. Thus, understanding the role of several genes can be used for the appropriate genetic diagnosis, research and in the clinical practice of POF.

Inhibin and premature ovarian failure

BACKGROUND

Elucidation of the causes of premature ovarian failure (POF) is difficult due to the heterogeneity of the condition. Inhibin is a potential candidate gene for POF based on its dual actions on FSH secretion by the pituitary and gametogenesis in the gonads. A missense mutation in the inhibin alpha subunit gene (INHA G769A) is associated with POF in several populations. However, there is phenotypic heterogeneity in INHA G769A mutation carriers.

METHODS

Relevant studies were identified by searching PubMed and mutational frequencies combined for meta-analysis.

RESULTS

Meta-analysis of published studies revealed a risk difference of 0.04 (-0.030 to 0.11). The occurrence of asymptomatic carriers in populations suggests incomplete penetrance and/or a multi-genetic cause of POF. We propose that a decline in inhibin bioactivity caused by the mutation could increase FSH levels; and in a susceptible individual, the heightened sensitivity to gonadotrophins causes POF. Impaired paracrine effects of inhibin could impact folliculogenesis due to reduced antagonism of activin, bone morphogenetic protein 15 and growth differentiation factor 9. Functional studies of this mutation indicate normal production of dimeric inhibin A and B and impaired bioactivity of inhibin B.

CONCLUSIONS

The identification of an autosomal mutation in the inhibin alpha subunit gene that is significantly linked to POF in certain ethnic populations highlights the role of inhibin in the regulation of ovarian biology and fertility. Although the reduction of inhibin B bioactivity by the INHA G769A mutation is clearly not the only cause, evidence suggests that this change may serve as a susceptibility factor, increasing the likelihood of POF.

Genetically modified mouse models for premature ovarian failure (POF)

Premature ovarian failure (POF) is a complex disorder that affects approximately 1% of women. POF is characterized by the depletion of functional ovarian follicles before the age of 40 years, and clinically, patients may present with primary amenorrhea or secondary amenorrhea. Although some genes have been hypothesized to be candidates responsible for POF, the etiology of most of the cases is idiopathic, with the underlying causes still unidentified because of the heterogeneity of the disease. In this review, we consider some mutant mouse models that exhibit phenotypes which are comparable to human POF, and we suggest that the use of these mouse models may help us to gain a better understanding of the molecular mechanisms underlying POF in humans.

Aging of the human ovary and testis

Aging is associated with structural and functional alterations in all organs of the human body. The aging of gonads represents in this respect a special case, because these organs are not functional for the whole lifespan of an individual and their normal function is not indispensable for functions of the rest of the body. Ovarian function lasts for the reproductive life of a woman, i.e., from menarche until menopause. The testicular endocrine function, in contrast, begins already in utero, is interrupted between neonatal life and puberty, and continues thereafter along with spermatogenesis, with only slight decline, until old age. The aging processes of the ovary and testis are therefore very different. We describe in this review the structural and functional alterations in the human ovary and testis upon aging. Special emphasis will be given to clinically significant alterations, which in women concern the causes and consequences of the individual variability of fertility during the latter part of the reproductive age. The clinically important aspect of testicular aging entails the decline of androgen production in aging men.

A challenge to the menopause stereotype: young Australian women's reflections of 'being diagnosed' as menopausal

This paper reports on a qualitative study designed to examine (i) possible explanations for difficulties young Australian women (under 40 years) encountered in the process of gaining a diagnosis of premature menopause and (ii) to address issues underpinning this aspect of menopause. Drawing on hermeneutic phenomenology, face-to-face interviews were carried out with 35 women who consented to share their experiences of 'being diagnosed' with premature menopause. The participants responded to an advertisement in a newspaper article, a radio announcement or through a menopause support centre. While all participants were located in Australia, larger numbers were from the metropolitan areas of Sydney, New South Wales, and Perth, Western Australia. This research reports that the process of finding an explanation for the physical and emotional symptoms the women were experiencing was very complex. The findings varied regarding the psychological and physical symptoms experienced, described feelings, and reasons that led to a diagnosis of menopause. This paper suggests that the age of the women and the non-specific symptoms experienced by them contributed significantly to the delay and uncertainty surrounding the experience of being diagnosed with premature menopause. There was uncertainty of the origin of symptoms, which led the women to feel as though they were 'going insane' or that it was 'all in their heads'. This frequently led to symptoms of menopause being attributed (by health professionals) to a psychiatric basis and menopause being overlooked for varying lengths of time.

[Genetic analysis of premature ovarian failure: role of forkhead and TGF-beta genes]

Premature ovarian failure is a common pathology affecting 1% of women. Although multiple etiologies have been described the majority of cases are idiopathic. Forkhead transcription factors as FOXL2 and FOXO3A are of particular interest in the research of genetic factors related with the pathology as they are present in diverse developmental pathways and ovarian physiology. Similarly, some TGF-beta factors (i.e. BMP 15 and GDF-9) have been demonstrated to play a key role in the regulation, at ovarian level, of female reproduction. In recent years numerous studies have been performed in order to elucidate the implication of these factors in the ovarian physiopathology. The aim of this manuscript is to describe some of these advances in the context of premature ovarian failure.

The 769G>A variant of the inhibin-alpha gene in Korean patients with preeclampsia

OBJECTIVE

Increased inhibin A serum and plasma levels in the second trimester are significantly associated with the development of preeclampsia. The measurement of inhibin A during early pregnancies may be helpful to predict those at risk of this disorder. The purpose of this study was to determine whether the 769G>A variant of the inhibin alpha (INHalpha) gene was associated with preeclampsia.

PATIENTS AND METHODS

We screened the 769G>A variation in 162 preeclamptic patients and in 202 normal pregnancies. The 769G>A variant of the INHalpha gene was determined by the PCR-based restriction fragment length polymorphism analysis and DNA sequencing.

RESULTS

We found no variation between the normal subjects and the preeclamptic patients.

CONCLUSION

The 769G>A variant of the INHalpha gene may be rare in Korean patients with preeclampsia.

Genetic variation in the inhibin pathway and risk of testicular germ cell tumors

Gene-knockout studies in mice suggest that INHA, encoding a subunit of gonadotropin-regulating proteins known as inhibins, is a tumor suppressor for testicular stromal cell tumors. It is not known whether genetic variation in the inhibin pathway also influences susceptibility to testicular germ cell tumors (TGCT), the most common testicular cancer in young men. To address this question, we conducted a case-control analysis (577 cases; 707 controls) of single-nucleotide polymorphisms (SNP) in genes in the inhibin pathway among participants in the U.S. Servicemen's Testicular Tumor Environmental and Endocrine Determinants Study. Thirty-eight tagging SNPs in six genes (INHA, INHBA, INHBB, INHBC, INHBE, and SMAD4) were genotyped. Odds ratios (OR) and 95% confidence intervals (CI) relating variant genotypes to TGCT risk were calculated using unconditional logistic regression. Among White subjects, an elevated risk of TGCT was observed for carriers of the T allele of the INHA variant rs2059693 (CT genotype: OR, 1.33; 95% CI, 1.04-1.71; TT: OR, 1.60; 95% CI, 1.01-2.52; P(trend) = 0.008). The association with rs2059693 was stronger for nonseminomas, and for teratomas and teratocarcinomas in particular (N = 58; CT: OR, 1.63; 95% CI, 0.89-2.99; TT: OR, 4.54; 95% CI 2.00-10.3; P(trend) = 0.0008). We found no evidence of association with variants in the other investigated genes. These findings suggest that genetic variation in the INHA locus influences TGCT development.

Recent advances in the study of genes involved in non-syndromic premature ovarian failure

Premature ovarian failure (POF) is a common pathology leading to infertility affecting about 1% of women under 40 years old. In POF patients, the ovarian dysfunction is characterized by the lack of the ovarian response to close a negative feedback loop on the synthesis of pituitary gonadotropins. Although the majority of cases are considered as idiopathic, diverse aetiologies have been associated, including genetic factors. Up to now, the potential genetic causes of non-syndromic POF have been established mainly by genetic linkage analysis of familial cases or by the screening of mutations in candidate genes based on animal models. Here, we review recent advances in the study of candidate genes.

Mutational analysis of BMP15 and GDF9 as candidate genes for premature ovarian failure

Mutational screening of the bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) genes in a population with premature ovarian failure (POF) identified no new mutations. However, three single nucleotide polymorphisms in the BMP15 gene, two in the 5' untranslated region (31T>G and 71C>G) and another in exon 1 (387G>A), were found to be common in both POF and control groups.

The genetic basis of premature ovarian failure

Premature ovarian failure (POF) is a common condition, affecting approximately 1:100 women. It is characterised by amenorrhea, hypoestrogenism, and elevated gonadotrophin levels in women under the age of 40. It is often an unexpected and distressing diagnosis, which coincides with infertility and menopausal symptoms. There is a well recognised genetic basis to the development of POF. Our laboratory has identified several candidate genes associated with POF.