Delayed puberty and hypogonadism caused by mutations in the follicle-stimulating hormone beta-subunit gene

Heterozygous ZNHIT3 variants within the 17q12 recurrent deletion region are associated with Mayer-Rokitansky-Kuster Hauser (MRKH) syndrome

The molecular basis of mullerian aplasia, also known as Mayer-Rokitansky-Kuster Hauser (MRKH) or congenital absence of the uterus and vagina, is largely unknown. We applied a multifaceted genetic approach to studying the pathogenesis of MRKH including exome sequencing of trios and duos, genome sequencing of families, qPCR, RT-PCR, and Sanger sequencing to detect intragenic deletions, insertions, splice variants, single nucleotide variants, and rearrangements in 132 persons with MRKH. We identified two heterozygous variants in ZNHIT3 localized to a commonly involved CNV region at chromosome 17q12 in two different families with MRKH. One is a frameshift, truncating variant that is predicted to interfere with steroid hormone binding of the LxxLL sequence of the C-terminal region. The second variant is a double missense/stopgain variant. Both variants impair protein expression in vitro. In addition, four more probands with MRKH harbored the stopgain variant without the nearby missense variant. In total, 6/132 (4.5%) of patients studied, including five with associated anomalies (type 2 MRKH), had ZNHIT3 variants that impair function in vitro. Our findings implicate ZNHIT3 as an important gene associated with MRKH within the 17q12 CNV region.

Restoring function to inactivating G protein-coupled receptor variants in the hypothalamic-pituitary-gonadal axis1

G protein-coupled receptors (GPCRs) are central to the functioning of the hypothalamic-pituitary-gonadal axis (HPG axis) and include the rhodopsin-like GPCR family members, neurokinin 3 receptor, kappa-opioid receptor, kisspeptin 1 receptor, gonadotropin-releasing hormone receptor, and the gonadotropin receptors, luteinizing hormone/choriogonadotropin receptor and follicle-stimulating hormone receptor. Unsurprisingly, inactivating variants of these receptors have been implicated in a spectrum of reproductive phenotypes, including failure to undergo puberty, and infertility. Clinical induction of puberty in patients harbouring such variants is possible, but restoration of fertility is not always a realisable outcome, particularly for those patients suffering from primary hypogonadism. Thus, novel pharmaceuticals and/or a fundamental change in approach to treating these patients are required. The increasing wealth of data describing the effects of coding-region genetic variants on GPCR function has highlighted that the majority appear to be dysfunctional as a result of misfolding of the encoded receptor protein, which, in turn, results in impaired receptor trafficking through the secretory pathway to the cell surface. As such, these intracellularly retained receptors may be amenable to 'rescue' using a pharmacological chaperone (PC)-based approach. PCs are small, cell permeant molecules hypothesised to interact with misfolded intracellularly retained proteins, stabilising their folding and promoting their trafficking through the secretory pathway. In support of the use of this approach as a viable therapeutic option, it has been observed that many rescued variant GPCRs retain at least a degree of functionality when 'rescued' to the cell surface. In this review, we examine the GPCR PC research landscape, focussing on the rescue of inactivating variant GPCRs with important roles in the HPG axis, and describe what is known regarding the mechanisms by which PCs restore trafficking and function. We also discuss some of the merits and obstacles associated with taking this approach forward into a clinical setting.

Core fucosylation regulates the ovarian response via FSH receptor during follicular development

INTRODUCTION

Ovarian low response to follicle-stimulating hormone (FSH) causes infertility featuring hypergonadotropic hypogonadism, ovarian failure, and/or defective ovarian response.

OBJECTIVES

N-glycosylation is essential for FSH receptor (FSHR). Core fucosylation catalyzed by fucosyltransferase 8 (FUT8) is the most common N-glycosylation. Core fucosylation level changes between individuals and plays important roles in multiple physiological and pathological conditions. This study aims to elucidate the significance of FUT8 to modulate FSHR function in female fertility.

METHODS

Samples from patients classified as poor ovary responders (PORs) were detected with lectin blot and real-time PCR. Fut8 gene knockout (Fut8-/-) mice and FUT8-knockdown human granulosa cell line (KGN-KD) were established and in vitro fertilization (IVF) assay, western blot, molecular interaction, immunofluorescence and immunoprecipitation were applied.

RESULTS

Core fucosylation is indispensable for oocyte and follicular development. FSHR is a highly core-fucosylated glycoprotein. Loss of core fucosylation suppressed binding of FSHR to FSH, and attenuated FSHR downstream signaling in granulosa cells. Transcriptomic analysis revealed the downregulation of several transcripts crucial for oocyte meiotic progression and preimplantation development in Fut8-/- mice and in POR patients. Furthermore, loss of FUT8 inhibited the interaction between granulosa cells and oocytes, reduced transzonal projection (TZP) formation and caused poor developmental competence of oocytes after fertilization in vitro. While L-fucose administration increased the core fucosylation of FSHR, and its sensitivity to FSH.

CONCLUSION

This study first reveals a significant presence of core fucosylation in female fertility control. Decreased fucosylation on FSHR reduces the interaction of FSH-FSHR and subsequent signaling, which is a feature of the POR patients. Our results suggest that core fucosylation controls oocyte and follicular development via the FSH/FSHR pathway and is essential for female fertility in mammals.

Identification of common genetic polymorphisms associated with down-regulated gonadotropin levels in an exome-wide association study

OBJECTIVE

To investigate whether common genetic polymorphisms are associated with gonadotropin levels after down-regulation with daily gonadotropin-releasing hormone agonist and whether the polymorphisms of candidate variants influence the ovarian response to exogenous gonadotropins.

DESIGN

Genetic association study.

SETTING

University-affiliated in vitro fertilization center.

PATIENTS

Subjects enrolled in an exploratory exome-wide association study (n = 862), a replication exome-wide association study (n = 86), and a classifier validation study (n = 148) were recruited from September 2016 to October 2018, September 2019 to September 2020, and January 2021 to December 2021, respectively. The included patients were aged ≤40 years and had a basal follicle-stimulating hormone (FSH) ≤12 IU/L.

INTERVENTIONS

All participants received a luteal phase down-regulation long protocol. Genome DNA was extracted from the peripheral blood leukocytes. For the exploratory and replication cohorts, exome sequencing was conducted on a HiSeq 2500 sequencing platform. The multiplex polymerase chain reaction amplification technique and next-generation sequencing also were performed in the exploratory and replication cohorts. For the samples of the validation cohort, Sanger sequencing was performed.

MAIN OUTCOME MEASURES

The primary endpoint was the gonadotropin levels after down-regulation, and the secondary endpoints were hormone levels and follicle diameters during stimulation, the total dose of FSH, duration of FSH stimulation, number of oocytes retrieved, and clinical pregnancy rate.

RESULTS

In the exploratory cohort, we identified that FSHB rs6169 (P=2.71 × 10-24) and its single-nucleotide polymorphisms in high linkage disequilibrium were associated with the down-regulated FSH level. The same locus was confirmed in the replication cohort. Women carrying the C allele of FSHB rs6169 exhibited higher average estradiol level during stimulation (P=6.82 × 10-5), shorter duration of stimulation, and less amount of exogenous FSH (Pduration=0.0002; Pdose=0.0024). In the independent validation set, adding rs6169 genotypes into the prediction model for FSH level after down-regulation enhanced the area under the curve from 0.560 to 0.712 in a logistic regression model, and increased prediction accuracy by 41.05% when a support vector machine classifier was applied.

CONCLUSION

The C allele of FSHB rs6169 is a susceptibility site for the relatively high level of FSH after down-regulation, which may be associated with increased ovarian FSH sensitivity.

Genetic variants of gonadotrophins and their receptors: Impact on the diagnosis and management of the infertile patient

This narrative review is concerned with genetic variants of the genes encoding gonadotrophin subunits and their receptors, as well as their implications into the diagnosis and treatment of infertility. We first review briefly the basics of molecular biology and biochemistry of gonadotrophin and gonadotrophin receptor structure and function, then describe the phenotypic effects of polymorphisms and mutations of these genes, followed by diagnostic aspects. We will then summarise the information that inactivating gonadotrophin receptor mutations have provided about the controversial topic of extragonadal gonadotrophin action. Finally, we will close with the current and future therapeutic approaches on patients with gonadotrophin and their receptor mutations.

The Genetic Backdrop of Hypogonadotropic Hypogonadism

The pituitary is an organ of dual provenance: the anterior lobe is epithelial in origin, whereas the posterior lobe derives from the neural ectoderm. The pituitary gland is a pivotal element of the axis regulating reproductive function in mammals. It collects signals from the hypothalamus, and by secreting gonadotropins (FSH and LH) it stimulates the ovary into cyclic activity resulting in a menstrual cycle and in ovulation. Pituitary organogenesis is comprised of three main stages controlled by different signaling molecules: first, the initiation of pituitary organogenesis and subsequent formation of Rathke’s pouch; second, the migration of Rathke’s pouch cells and their proliferation; and third, lineage determination and cellular differentiation. Any disruption of this sequence, e.g., gene mutation, can lead to numerous developmental disorders. Gene mutations contributing to disordered pituitary development can themselves be classified: mutations affecting transcriptional determinants of pituitary development, mutations related to gonadotropin deficiency, mutations concerning the beta subunit of FSH and LH, and mutations in the DAX-1 gene as a cause of adrenal hypoplasia and disturbed responsiveness of the pituitary to GnRH. All these mutations lead to disruption in the hypothalamic–pituitary–ovarian axis and contribute to the development of primary amenorrhea.

Effect of age at first egg on reproduction performance and characterization of the hypothalamo-pituitary-gonadal axis in chickens

As an important indicator of sexual maturity of hens, age at first egg (AFE) is significantly associated with reproduction performance. In this study, 400 hens were divided into 6 groups based on AFE to analyze the difference of reproduction performance, reproduction hormone levels and the characterization of the hypothalamo-pituitary-gonadal axis in chickens. The results showed that the egg production of the hens in the late-maturing groups was significantly lower than that of the ones in other groups and the precocious hens had a lower egg production rate. The hens in late-maturing group had a lower fertility rate, LH levels and shorter duration of peak of egg production (PEP), the precocious hens had lower PRL levels. In addition, the characterization of the hypothalamo-pituitary-gonadal axis showed that the individuals with normal AFE had higher GNRH, GNRHR, ESR1, KITLG, and CYP11A1 expression levels than late-maturing and precocious individuals, which indicated that the chickens with normal AFE advantages on reproduction regulation system.

Genetics of hypogonadotropic Hypogonadism-Human and mouse genes, inheritance, oligogenicity, and genetic counseling

Hypogonadotropic hypogonadism, which may be normosmic (nHH) or anosmic/hyposmic, known as Kallmann syndrome (KS), is due to gonadotropin-releasing hormone deficiency, which results in absent puberty and infertility. Investigation of the genetic basis of nHH/KS over the past 35 years has yielded a substantial increase in our understanding, as variants in 44 genes in OMIM account for ~50% of cases. The first genes for KS (ANOS1) and nHH (GNRHR) were followed by the discovery that FGFR1 variants may cause either nHH or KS. Associated anomalies include midline facial defects, neurologic deficits, cardiac anomalies, and renal agenesis, among others. Mouse models for all but one gene (ANOS1) generally support findings in humans. About half of the known genes implicated in nHH/KS are inherited as autosomal dominant and half are autosomal recessive, whereas only 7% are X-linked recessive. Digenic and oligogenic inheritance has been reported in 2-20% of patients, most commonly with variants in genes that may result in either nHH or KS inherited in an autosomal dominant fashion. In vitro analyses have only been conducted for both gene variants in eight cases and for one gene variant in 20 cases. Rigorous confirmation that two gene variants in the same individual cause the nHH/KS phenotype is lacking for most. Clinical diagnosis is probably best accomplished by targeted next generation sequencing of the known candidate genes with confirmation by Sanger sequencing. Elucidation of the genetic basis of nHH/KS has resulted in an enhanced understanding of this disorder, as well as normal puberty, which makes genetic diagnosis clinically relevant.

Perspectives on the development and future of oocyte IVM in clinical practice

Oocyte in vitro maturation (IVM) is an assisted reproductive technology designed to obtain mature oocytes following culture of immature cumulus–oocyte complexes collected from antral follicles. Although IVM has been practiced for decades and is no longer considered experimental, the uptake of IVM in clinical practice is currently limited. The purpose of this review is to ensure reproductive medicine professionals understand the appropriate use of IVM drawn from the best available evidence supporting its clinical potential and safety in selected patient groups. This group of scientists and fertility specialists, with expertise in IVM in the ART laboratory and/or clinic, explore here the development of IVM towards acquisition of a non-experimental status and, in addition, critically appraise the current and future role of IVM in human ART.

Distal Enhancer Potentiates Activin- and GnRH-Induced Transcription of FSHB

FSH is critical for fertility. Transcription of FSHB, the gene encoding the beta subunit, is rate-limiting in FSH production and is regulated by both GnRH and activin. Activin signals through SMAD transcription factors. Although the mechanisms and importance of activin signaling in mouse Fshb transcription are well-established, activin regulation of human FSHB is less well understood. We previously reported a novel enhancer of FSHB that contains a fertility-associated single nucleotide polymorphism (rs10031006) and requires a region resembling a full (8 base-pair) SMAD binding element (SBE). Here, we investigated the role of the putative SBE within the enhancer in activin and GnRH regulation of FSHB. In mouse gonadotrope-derived LβT2 cells, the upstream enhancer potentiated activin induction of both the human and mouse FSHB proximal promoters and conferred activin responsiveness to a minimal promoter. Activin induction of the enhancer required the SBE and was blocked by the inhibitory SMAD7, confirming involvement of the classical SMAD signaling pathway. GnRH induction of FSHB was also potentiated by the enhancer and dependent on the SBE, consistent with known activin/GnRH synergy regulating FSHB transcription. In DNA pull-down, the enhancer SBE bound SMAD4, and chromatin immunoprecipitation demonstrated SMAD4 enrichment at the enhancer in native chromatin. Combined activin/GnRH treatment elevated levels of the active transcriptional histone marker, histone 3 lysine 27 acetylation, at the enhancer. Overall, this study indicates that the enhancer is directly targeted by activin signaling and identifies a novel, evolutionarily conserved mechanism by which activin and GnRH can regulate FSHB transcription.

Reduced FSH and LH action: implications for medically assisted reproduction

Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) play complementary roles in follicle development and ovulation via a complex interaction in the hypothalamus, anterior pituitary gland, reproductive organs, and oocytes. Impairment of the production or action of gonadotropins causes relative or absolute LH and FSH deficiency that compromises gametogenesis and gonadal steroid production, thereby reducing fertility. In women, LH and FSH deficiency is a spectrum of conditions with different functional or organic causes that are characterized by low or normal gonadotropin levels and low oestradiol levels. While the causes and effects of reduced LH and FSH production are very well known, the notion of reduced action has received less attention by researchers. Recent evidence shows that molecular characteristics, signalling as well as ageing, and some polymorphisms negatively affect gonadotropin action. These findings have important clinical implications, in particular for medically assisted reproduction in which diminished action determined by the afore-mentioned factors, combined with reduced endogenous gonadotropin production caused by GnRH analogue protocols, may lead to resistance to gonadotropins and, thus, to an unexpected hypo-response to ovarian stimulation. Indeed, the importance of LH and FSH action has been highlighted by the International Committee for Monitoring Assisted Reproduction Technologies (ICMART) in their definition of hypogonadotropic hypogonadism as gonadal failure associated with reduced gametogenesis and gonadal steroid production due to reduced gonadotropin production or action. The aim of this review is to provide an overview of determinants of reduced FSH and LH action that are associated with a reduced response to ovarian stimulation.

Next Generation Sequencing Should Be Proposed to Every Woman With "Idiopathic" Primary Ovarian Insufficiency

Context

Primary ovarian insufficiency (POI) affects 1% of women under 40 years of age. POI is idiopathic in more than 70% of cases. Though many candidate genes have been identified in recent years, the prevalence and pathogenicity of abnormalities are still difficult to establish.

Objective

Our primary objective was to evaluate the prevalence of gene variations in a large prospective multicentric POI cohort. Our secondary objective was to evaluate the correlation between phenotype and genotype.

Methods

Two hundred and sixty-nine well-phenotyped POI patients were screened for variants of 18 known POI genes (BMP15, DMC1, EIF2S2, FIGLA, FOXL2, FSHR, GDF9, GPR3, HFM1, LHX8, MSH5, NOBOX, NR5A1, PGRMC1, STAG3, XPNPEP2, BHLB, and FSHB) by next generation sequencing (NGS). Abnormalities were classified as "variant" or "variant of unknown signification" (VUS) according to available functional tests or algorithms (SIFT, Polyphen-2, MutationTaster).

Results

One hundred and two patients (38%) were identified as having at least 1 genetic abnormality. Sixty-seven patients (25%) presented at least 1 variant. Forty-eight patients presented at least 1 VUS (18%). Thirteen patients (5%) had combined abnormalities. NOBOX variants were the most common gene variants involved in POI (9%). Interestingly, we saw no significant differences in the previous family history of POI, ethnic origin, age at onset of POI, primary amenorrhea, or secondary menstrual disturbances between the different genotypes.

Conclusion

In our study, a high percentage of patients presented gene variants detected by NGS analysis (38%). Every POI patient should undergo NGS analysis to improve medical cares of the patients.

FSHB Transcription is Regulated by a Novel 5' Distal Enhancer With a Fertility-Associated Single Nucleotide Polymorphism

The pituitary gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone, signal the gonads to regulate male and female fertility. FSH is critical for female fertility as it regulates oocyte maturation, ovulation, and hormone synthesis. Multiple genome-wide association studies (GWAS) link a 130 Kb locus at 11p14.1, which encompasses the FSH beta-subunit (FSHB) gene, with fertility-related traits that include polycystic ovary syndrome, age of natural menopause, and dizygotic twinning. The most statistically significant single nucleotide polymorphism from several GWAS studies (rs11031006) resides within a highly conserved 450 bp region 26 Kb upstream of the human FSHB gene. Given that sequence conservation suggests an important biological function, we hypothesized that the region could regulate FSHB transcription. In luciferase assays, the conserved region enhanced FSHB transcription and gel shifts identified a binding site for Steroidogenic factor 1 (SF1) contributing to its function. Analysis of mouse pituitary single-cell ATAC-seq demonstrated open chromatin at the conserved region exclusive to a gonadotrope cell-type cluster. Additionally, enhancer-associated histone markers were identified by immunoprecipitation of chromatin from mouse whole pituitary and an immortalized mouse gonadotrope-derived LβT2 cell line at the conserved region. Furthermore, we found that the rs11031006 minor allele upregulated FSHB transcription via increased SF1 binding to the enhancer. All together, these results identify a novel upstream regulator of FSHB transcription and indicate that rs11031006 can modulate FSH levels.

Delayed and Precocious Puberty: Genetic Underpinnings and Treatments

Delayed puberty may signify a common variation of normal development, or indicate the presence of a pathologic process. Constitutional delay of growth and puberty is a strongly familial type of developmental pattern and accounts for the vast majority of children who are "late bloomers." Individuals with sex chromosomal abnormalities frequently have hypergonadotropic hypogonadism. There are currently 4 known monogenic causes of central precocious puberty. The primary treatment goal in children with hypogonadism is to mimic normal pubertal progression, while the primary aims for the management of precocious puberty are preservation of height potential and prevention of further pubertal development.

Genes predisposing to syndromic and nonsyndromic infertility: a narrative review

Background

Advanced biological techniques have helped produce more insightful findings on the genetic etiology of infertility that may lead to better management of the condition. This review provides an update on genes predisposing to syndromic and nonsyndromic infertility.

Main body

The review identified 65 genes linked with infertility and infertility-related disorders. These genes regulate fertility. However, mutational loss of the functions of the genes predisposes to infertility. Twenty-three (23) genes representing 35% were linked with syndromic infertility, while 42 genes (65%) cause nonsyndromic infertility. Of the 42 nonsyndromic genes, 26 predispose to spermatogenic failure and sperm morphological abnormalities, 11 cause ovarian failures, and 5 cause sex reversal and puberty delay. Overall, 31 genes (48%) predispose to male infertility, 15 genes (23%) cause female infertility, and 19 genes (29%) predispose to both. The common feature of male infertility was spermatogenic failure and sperm morphology abnormalities, while ovarian failure has been the most frequently reported among infertile females. The mechanisms leading to these pathologies are gene-specific, which, if targeted in the affected, may lead to improved treatment.

Conclusions

Mutational loss of the functions of some genes involved in the development and maintenance of fertility may predispose to syndromic or nonsyndromic infertility via gene-specific mechanisms. A treatment procedure that targets the affected gene(s) in individuals expressing infertility may lead to improved treatment.

Study of frequency and types of chromosomal abnormalities in phenotypically female patients with amenorrhea in Eastern Indian population

AIM

This comprehensive review article aims to comprehend the frequency and prevalence of chromosomal abnormalities in both primary amenorrhea (PA) and secondary amenorrhea (SA) cases and correlating it with their phenotypes, clinical features and hormonal profiles.

METHODS

Research publications on prevalence of chromosomal abnormalities in both PA and SA cases worldwide and its etiology, clinical features, hormonal profiles; their correlation with chromosomal profiles were searched for on the internet, including general search engines and respective scientific sites. Only published, relevant and authentic data conducted on phenotypically female patients were considered. Another aspect of amenorrhea occurs due to several clinical conditions apart from cytogenetic viewpoint were not considered or discussed in detail.

RESULTS

As literature study suggests; considering various etiology of amenorrhea counting anatomic defect of the hypothalamus or genetic defect, and various acquired causes of chromosomal anomalies contribute to be one of the major etiologies of both PA and SA; ranging from 15.9% to 63.3% in case of PA and from 3.9% to 44.4% in case of SA. In spite of the presence of any other factors responsible condition, the genetic factors need to be emphasized, which might include single gene disorders or chromosomal disorders. Individuals with chromosomal anomalies reported a wide range of abnormalities in phenotypes, as well as in other clinical features and hormonal profiles.

CONCLUSION

This comprehensive review is the first structured review article that encompasses the cytogenetic profile of the amenorrhea cases and correlating it with their phenotypes, clinical features and hormonal profiles from Eastern India.

Clinical and genetic analysis of an isolated follicle-stimulating hormone deficiency female patient

OBJECTIVE

To characterize the clinical features of a female patient with isolated follicle-stimulating hormone (FSH) deficiency and to investigate the underlying mechanisms of FSH inactivation.

METHODS

The proband was a 29-year-old woman with primary amenorrhea, impaired pubertal development, and infertility. Subsequently, reproductive endocrine was screened. DNA sequencing was conducted for the identification of FSHβ mutation. RT-PCR, western blots, in vitro immunometric assay, and bioassay were performed to confirm the impact of the mutation on FSH expression and biological activity. Molecular model consisting of FSHα and mutant FSHβ subunit was built for the structural analysis of FSH protein.

RESULTS

The evaluation of reproductive endocrine revealed undetectable basal and GnRH-stimulated serum FSH. Sequencing of the FSHβ gene identified a homozygous nonsense mutation at codon 97 (Arg97X). RT-PCR and western blot analysis revealed the mutation Arg97X did not affect FSHβ mRNA and protein expression. But in vitro immunometric assay and bioassay demonstrated the production of normal bioactive FSH protein was disturbed by the mutation Arg97X. Structural analysis showed the surface structure of the resulting mutant FSH presented with lock-and-key, mosaic binding pattern, while the native structure was an encircling binding mode.

CONCLUSION

The mutation Arg97X could disturb structural stability of the resulting FSH protein consisting of FSHα and mutant FSHβ subunit, which may lead to FSH deficiency.

Genetics of congenital hypogonadotropic hypogonadism: peculiarities and phenotype of an oligogenic disease

A genetic basis of congenital isolated hypogonadotropic hypogonadism (CHH) can be defined in almost 50% of cases, albeit not necessarily the complete genetic basis. Next-generation sequencing (NGS) techniques have led to the discovery of a great number of loci, each of which has illuminated our understanding of human gonadotropin-releasing hormone (GnRH) neurons, either in respect of their embryonic development or their neuroendocrine regulation as the "pilot light" of human reproduction. However, because each new gene linked to CHH only seems to underpin another small percentage of total patient cases, we are still far from achieving a comprehensive understanding of the genetic basis of CHH. Patients have generally not benefited from advances in genetics in respect of novel therapies. In most cases, even genetic counselling is limited by issues of apparent variability in expressivity and penetrance that are likely underpinned by oligogenicity in respect of known and unknown genes. Robust genotype-phenotype relationships can generally only be established for individuals who are homozygous, hemizygous or compound heterozygotes for the same gene of variant alleles that are predicted to be deleterious. While certain genes are purely associated with normosmic CHH (nCHH) some purely with the anosmic form (Kallmann syndrome-KS), other genes can be associated with both nCHH and KS-sometimes even within the same kindred. Even though the anticipated genetic overlap between CHH and constitutional delay in growth and puberty (CDGP) has not materialised, previously unanticipated genetic relationships have emerged, comprising conditions of combined (or multiple) pituitary hormone deficiency (CPHD), hypothalamic amenorrhea (HA) and CHARGE syndrome. In this review, we report the current evidence in relation to phenotype and genetic peculiarities regarding 60 genes whose loss-of-function variants can disrupt the central regulation of reproduction at many levels: impairing GnRH neurons migration, differentiation or activation; disrupting neuroendocrine control of GnRH secretion; preventing GnRH neuron migration or function and/or gonadotropin secretion and action.

Genome-wide association and epidemiological analyses reveal common genetic origins between uterine leiomyomata and endometriosis

Uterine leiomyomata (UL) are the most common neoplasms of the female reproductive tract and primary cause for hysterectomy, leading to considerable morbidity and high economic burden. Here we conduct a GWAS meta-analysis in 35,474 cases and 267,505 female controls of European ancestry, identifying eight novel genome-wide significant (P < 5 × 10^-8) loci, in addition to confirming 21 previously reported loci, including multiple independent signals at 10 loci. Phenotypic stratification of UL by heavy menstrual bleeding in 3409 cases and 199,171 female controls reveals genome-wide significant associations at three of the 29 UL loci: 5p15.33 (TERT), 5q35.2 (FGFR4) and 11q22.3 (ATM). Four loci identified in the meta-analysis are also associated with endometriosis risk; an epidemiological meta-analysis across 402,868 women suggests at least a doubling of risk for UL diagnosis among those with a history of endometriosis. These findings increase our understanding of genetic contribution and biology underlying UL development, and suggest overlapping genetic origins with endometriosis.

A TAC3 Missense Variant in a Domestic Shorthair Cat with Testicular Hypoplasia and Persistent Primary Dentition

A single male domestic shorthair cat that did not complete puberty was reported. At four years of age, it still had primary dentition, testicular hypoplasia, and was relatively small for its age. We hypothesized that the phenotype might have been due to an inherited form of hypogonadotropic hypogonadism (HH). We sequenced the genome of the affected cat and compared the data to 38 genomes from control cats. A search for private variants in 40 candidate genes associated with human HH revealed a single protein-changing variant in the affected cat. It was located in the TAC3 gene encoding tachykinin 3, a precursor protein of the signaling molecule neurokinin B, which is known to play a role in sexual development. TAC3 variants have been reported in human patients with HH. The identified feline variant, TAC3:c.220G>A or p.(Val74Met), affects a moderately conserved region of the precursor protein, 11 residues away from the mature neurokinin B sequence. The affected cat was homozygous for the mutant allele. In a cohort of 171 randomly sampled cats, 169 were homozygous for the wildtype allele and 2 were heterozygous. These data tentatively suggest that the identified TAC3 variant might have caused the suppression of puberty in the affected cat.

Delayed Puberty-Phenotypic Diversity, Molecular Genetic Mechanisms, and Recent Discoveries

This review presents a comprehensive discussion of the clinical condition of delayed puberty, a common presentation to the pediatric endocrinologist, which may present both diagnostic and prognostic challenges. Our understanding of the genetic control of pubertal timing has advanced thanks to active investigation in this field over the last two decades, but it remains in large part a fascinating and mysterious conundrum. The phenotype of delayed puberty is associated with adult health risks and common etiologies, and there is evidence for polygenic control of pubertal timing in the general population, sex-specificity, and epigenetic modulation. Moreover, much has been learned from comprehension of monogenic and digenic etiologies of pubertal delay and associated disorders and, in recent years, knowledge of oligogenic inheritance in conditions of GnRH deficiency. Recently there have been several novel discoveries in the field of self-limited delayed puberty, encompassing exciting developments linking this condition to both GnRH neuronal biology and metabolism and body mass. These data together highlight the fascinating heterogeneity of disorders underlying this phenotype and point to areas of future research where impactful developments can be made.

The Role of the Brain in the Pathogenesis and Physiology of Polycystic Ovary Syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder, affecting at least 10% of women of reproductive age. PCOS is typically characterized by the presence of at least two of the three cardinal features of hyperandrogenemia (high circulating androgen levels), oligo- or anovulation, and cystic ovaries. Hyperandrogenemia increases the severity of the condition and is driven by increased luteinizing hormone (LH) pulse secretion from the pituitary. Indeed, PCOS women display both elevated mean LH levels, as well as an elevated frequency of LH pulsatile secretion. The abnormally high LH pulse frequency, reflective of a hyperactive gonadotropin-releasing hormone (GnRH) neural circuit, suggests a neuroendocrine basis to either the etiology or phenotype of PCOS. Several studies in preclinical animal models of PCOS have demonstrated alterations in GnRH neurons and their upstream afferent neuronal circuits. Some rodent PCOS models have demonstrated an increase in GnRH neuron activity that correlates with an increase in stimulatory GABAergic innervation and postsynaptic currents onto GnRH neurons. Additional studies have identified robust increases in hypothalamic levels of kisspeptin, another potent stimulator of GnRH neurons. This review outlines the different brain and neuroendocrine changes in the reproductive axis observed in PCOS animal models, discusses how they might contribute to either the etiology or adult phenotype of PCOS, and considers parallel findings in PCOS women.

Isolated follicle-stimulating hormone (FSH) deficiency in two infertile men without FSH β gene mutation: Case report and literature review

OBJECTIVE

Congenital FSH deficiency is an exceptional cause of male infertility most often attributed to FSH β gene mutations. The few published cases report azoospermia, severe testicular hypotrophy and normal testosterone levels associated with normal virilization. We report the exploration of two young men aged 26 and 27 years with severe sperm abnormalities, moderate testicular hypotrophy and isolated FSH deficiency.

METHODS

Several FSH, LH, total testosterone and inhibin B assays and FSH β gene sequencing were performed.

RESULTS

FSH was almost undetectable at baseline and poorly responsive to GnRH test, whereas LH was normal at baseline and increased after GnRH test. Testosterone levels were within the adult range, while inhibin B levels were upper-normal to high. No FSH β gene mutations were found. Exogenous FSH treatment was followed by spontaneous pregnancy in one case and required intra-cytoplasmic sperm injection (ICSI) in the other.

CONCLUSIONS

The paradoxical high levels of inhibin B reflect the presence of functional Sertoli cells and may explain the isolated FSH deficiency. An intra-gonadal factor stimulating inhibin B secretion is discussed.

FSH β-subunit mutations in two sisters: the first report from the Indian sub-continent and review of previous cases

Isolated FSH deficiency due to mutations in the gene for β-subunit of FSH is an extremely rare autosomal recessive disease of which only eleven cases have been reported so far. The clinical features include absent breast development and primary amenorrhea in females and azoospermia with normal testosterone levels in males. In this study we report two Kashmiri sisters born to native Kashmiri consanguineous parents with failure of onset of puberty. Hormonal evaluation revealed undetectable serum FSH and estradiol and high LH. Genetic analysis of FSH β-gene identified one nonsense mutation (c.343C > T:p. Arg115Stop) in exon 3. The two sisters were homozygous for this nonsense mutation while the parents were heterozygous. Incorporation of a stop codon at 115 codon position is predicted to result in the formation of truncated FSH β protein, lacking 14 amino acid from the carboxy-terminus (p.Arg115Stop). Very recently, this same mutation was reported for the first time in a Chinese male. Ours is the first ever report of any FSH β-subunit mutation from the Indian sub-continent and this particular mutation in any female from anywhere in the world. We conclude and emphasize that this diagnosis should be considered in girls with delayed puberty and selective deficiency of FSH.

The Genetic Basis of Delayed Puberty

Delayed pubertal onset has many etiologies, but on average two-thirds of patients presenting with late puberty have self-limited (or constitutional) delayed puberty. Self-limited delayed puberty often has a strong familial basis. Segregation analyses from previous studies show complex models of inheritance, most commonly autosomal dominant, but also including autosomal recessive, bilineal, and X-linked. Sporadic cases are also observed. Despite this, the neuroendocrine mechanisms and genetic regulation remain unclear in the majority of patients with self-limited delayed puberty. Only rarely have mutations in genes known to cause aberrations of the hypothalamic-pituitary-gonadal axis been identified in cases of delayed puberty, and the majority of these are in relatives of patients with congenital hypogonadotropic hypogonadism (CHH), for example in the FGFR1 and GNRHR genes. Using next generation sequencing in a large family with isolated self-limited delayed puberty, a pathogenic mutation in the CHH gene HS6ST1 was found as the likely cause for this phenotype. Additionally, a study comparing the frequency of mutations in genes that cause GnRH deficiency between probands with CHH and probands with isolated self-limited delayed puberty identified that a significantly higher proportion of mutations with a greater degree of oligogenicity were seen in the CHH group. Mutations in the gene IGSF10 have been implicated in the pathogenesis of familial late puberty in a large Finnish cohort. IGSF10 disruption represents a fetal origin of delayed puberty, with dysregulation of GnRH neuronal migration during embryonic development presenting for the first time in adolescence as late puberty. Some patients with self-limited delayed puberty have distinct constitutional features of growth and puberty. Deleterious variants in FTO have been found in families with delayed puberty with extremely low BMI and maturational delay in growth in early childhood. Recent exciting evidence highlights the importance of epigenetic up-regulation of GnRH transcription by a network of miRNAs and transcription factors, including EAP1, during puberty. Whilst a fascinating heterogeneity of genetic defects have been shown to result in delayed and disordered puberty, and many are yet to be discovered, genetic testing may become a realistic diagnostic tool for the differentiation of conditions of delayed puberty.

Genes underlying delayed puberty

The genetic control of pubertal timing has been a field of active investigation for the last decade, but remains a fascinating and mysterious conundrum. Self-limited delayed puberty (DP), also known as constitutional delay of growth and puberty, represents the extreme end of normal pubertal timing, and is the commonest cause of DP in both boys and girls. Familial self-limited DP has a clear genetic basis. It is a highly heritable condition, which often segregates in an autosomal dominant pattern (with or without complete penetrance) in the majority of families. However, the underlying neuroendocrine pathophysiology and genetic regulation has been largely unknown. Very recently novel gene discoveries from next generation sequencing studies have provided insights into the genetic mutations that lead to familial DP. Further understanding has come from sequencing genes known to cause GnRH deficiency, next generation sequencing studies in patients with early puberty, and from large-scale genome wide association studies in the general population. Results of these studies suggest that the genetic basis of DP is likely to be highly heterogeneous. Abnormalities of GnRH neuronal development, function, and its downstream pathways, metabolic and energy homeostatic derangements, and transcriptional regulation of the hypothalamic-pituitary-gonadal axis may all lead to DP. This variety of different pathogenic mechanisms affecting the release of the puberty 'brake' may take place in several age windows between fetal life and puberty.

The gonadotropin system, lessons from animal models and clinical cases

This review article centers upon family of gonadotropin hormones which consists of two pituitary hormones - follicle-stimulating hormone (FSH) and luteinizing hormone (LH) as well as one non-pituitary hormone - human chorionic gonadotropin (hCG) secreted by placenta, and their receptors. Gonadotropins play an essential role in proper sexual development, puberty, gametogenesis, maintenance of pregnancy and male sexual differentiation during the fetal development. They belong to the family of glycoprotein hormones thus they constitute heterodimeric proteins built of common α subunit and hormone-specific β-subunit. Hitherto, several mutations in genes encoding both gonadotropins and their receptors have been identified in humans. Their occurrence resulted in a number of different phenotypes including delayed puberty, primary amenorrhea, hermaphroditism, infertility and hypogonadism. In order to understand the effects of mutations on the phenotype observed in affected patients, detailed molecular studies are required to map the relationship between the structure and function of gonadotropins and their receptors. Nonetheless, in vitro assays are often insufficient to understand physiology. Therefore, several animal models have been developed to unravel the physiological roles of gonadotropins and their receptors.

Molecular regulation of follicle-stimulating hormone synthesis, secretion and action

Follicle-stimulating hormone (FSH) plays fundamental roles in male and female fertility. FSH is a heterodimeric glycoprotein expressed by gonadotrophs in the anterior pituitary. The hormone-specific FSHβ-subunit is non-covalently associated with the common α-subunit that is also present in the luteinizing hormone (LH), another gonadotrophic hormone secreted by gonadotrophs and thyroid-stimulating hormone (TSH) secreted by thyrotrophs. Several decades of research led to the purification, structural characterization and physiological regulation of FSH in a variety of species including humans. With the advent of molecular tools, availability of immortalized gonadotroph cell lines and genetically modified mouse models, our knowledge on molecular mechanisms of FSH regulation has tremendously expanded. Several key players that regulate FSH synthesis, sorting, secretion and action in gonads and extragonadal tissues have been identified in a physiological setting. Novel post-transcriptional and post-translational regulatory mechanisms have also been identified that provide additional layers of regulation mediating FSH homeostasis. Recombinant human FSH analogs hold promise for a variety of clinical applications, whereas blocking antibodies against FSH may prove efficacious for preventing age-dependent bone loss and adiposity. It is anticipated that several exciting new discoveries uncovering all aspects of FSH biology will soon be forthcoming.

GENETICS IN ENDOCRINOLOGY: Genetic counseling for congenital hypogonadotropic hypogonadism and Kallmann syndrome: new challenges in the era of oligogenism and next-generation sequencing

Congenital hypogonadotropic hypogonadism (CHH) and Kallmann syndrome (KS) are rare, related diseases that prevent normal pubertal development and cause infertility in affected men and women. However, the infertility carries a good prognosis as increasing numbers of patients with CHH/KS are now able to have children through medically assisted procreation. These are genetic diseases that can be transmitted to patients' offspring. Importantly, patients and their families should be informed of this risk and given genetic counseling. CHH and KS are phenotypically and genetically heterogeneous diseases in which the risk of transmission largely depends on the gene(s) responsible(s). Inheritance may be classically Mendelian yet more complex; oligogenic modes of transmission have also been described. The prevalence of oligogenicity has risen dramatically since the advent of massively parallel next-generation sequencing (NGS) in which tens, hundreds or thousands of genes are sequenced at the same time. NGS is medically and economically more efficient and more rapid than traditional Sanger sequencing and is increasingly being used in medical practice. Thus, it seems plausible that oligogenic forms of CHH/KS will be increasingly identified making genetic counseling even more complex. In this context, the main challenge will be to differentiate true oligogenism from situations when several rare variants that do not have a clear phenotypic effect are identified by chance. This review aims to summarize the genetics of CHH/KS and to discuss the challenges of oligogenic transmission and also its role in incomplete penetrance and variable expressivity in a perspective of genetic counseling.

Ovarian Follicular Theca Cell Recruitment, Differentiation, and Impact on Fertility: 2017 Update

The major goal of this review is to summarize recent exciting findings that have been published within the past 10 years that, to our knowledge, have not been presented in detail in previous reviews and that may impact altered follicular development in polycystic ovarian syndrome (PCOS) and premature ovarian failure in women. Specifically, we will cover the following: (1) mouse models that have led to discovery of the derivation of two precursor populations of theca cells in the embryonic gonad; (2) the key roles of the oocyte-derived factor growth differentiation factor 9 on the hedgehog (HH) signaling pathway and theca cell functions; and (3) the impact of the HH pathway on both the specification of theca endocrine cells and theca fibroblast and smooth muscle cells in developing follicles. We will also discuss the following: (1) other signaling pathways that impact the differentiation of theca cells, not only luteinizing hormone but also insulinlike 3, bone morphogenic proteins, the circadian clock genes, androgens, and estrogens; and (2) theca-associated vascular, immune, and fibroblast cells, as well as the cytokines and matrix factors that play key roles in follicle growth. Lastly, we will integrate what is known about theca cells from mouse models, human-derived theca cell lines from patients who have PCOS and patients who do not have PCOS, and microarray analyses of human and bovine theca to understand what pathways and factors contribute to follicle growth as well as to the abnormal function of theca.

Genetic analysis of Mayer-Rokitansky-Kuster-Hauser syndrome in a large cohort of families

OBJECTIVE

To study the genetic cause of Mayer-Rokitansky-Kuster-Hauser syndrome (MRKH). Although a few candidate genes and genomic domains for have been reported for MRKH, the genetic underpinnings remain largely unknown. Some of the top candidate genes are WNT4, HNF1B, and LHX1. The goals of this study were to: 1) determine the prevalence of WNT4, HNF1B, and LHX1 point mutations, as well as new copy number variants (CNVs) in people with MRKH; and 2) identify and characterize MRKH cohorts.

DESIGN

Laboratory- and community-based study.

SETTING

Academic medical centers.

PATIENT(S)

A total of 147 MRKH probands and available family members.

INTERVENTIONS(S)

DNA sequencing of WNT4, HNF1B, and LHX1 in 100 MRKH patients, chromosomal microarray analysis in 31 North American MRKH patients, and characterization and sample collection of 147 North American and Turkish MRKH probands and their families.

MAIN OUTCOME MEASURE(S)

DNA sequence variants and CNVs; pedigree structural analysis.

RESULT(S)

We report finding CNVs in 6/31 people (∼19%) with MRKH, but no point mutations or small indels in WNT4, HNF1B, or LHX1 in 100 MRKH patients. Our MRKH families included 43 quads, 26 trios, and 30 duos. Of our MRKH probands, 87/147 (59%) had MRKH type 1 and 60/147 (41%) had type 2 with additional anomalies.

CONCLUSION(S)

Although the prevalence of WNT4, HNF1B, and LHX1 point mutations is low in people with MRKH, the prevalence of CNVs was ∼19%. Further analysis of our large familial cohort of patients will facilitate gene discovery to better understand the complex etiology of MRKH.

Clinical and Hormonal Features of a Male Adolescent with Congenital Isolated Follicle-Stimulating Hormone Deficiency

AIM

Our aim was to describe the clinical and genetic findings in an adolescent male with isolated follicle-stimulating hormone (FSH) deficiency and demonstrate the efficacy of recombinant human FSH (rhFSH) replacement in this case.

METHODS

A 14.5-year-old adolescent male was referred with normal pubertal development and small testes. Serum testosterone, FSH, and luteinising hormone (LH) were measured at baseline and after gonadotropin-releasing hormone (GnRH) stimulation. Testicular biopsy was performed, and rhFSH replacement was administered for 6 months. The patient's FSHβ gene was amplified and sequenced.

RESULTS

Basal and GnRH-stimulated FSH levels were undetectable, in contrast with increased LH levels under both conditions. Histopathological investigation of a testicular biopsy specimen revealed a reduced number of Sertoli cells, the absence of germ cells, Leydig cell hyperplasia, and a thickened basement membrane in seminiferous tubules. The testicular size changed from 1 ml at baseline to 6 ml after 6 months of rhFSH replacement. Sequencing of the FSHβ gene exon 3 revealed a new missense mutation (c.364T>C, resulting in p.Cys122Arg) in a homozygous state in the patient; both parents and a sister carried the same mutation in a heterozygous state. We also compared our case with all similar cases published previously.

CONCLUSION

We herein described an adolescent male with isolated FSH deficiency due to a novel FSHβ gene mutation associated with a prepubertal testes size and normal virilisation.

Targeted next generation sequencing approach identifies eighteen new candidate genes in normosmic hypogonadotropic hypogonadism and Kallmann syndrome

The genetic basis is unknown for ∼60% of normosmic hypogonadotropic hypogonadism (nHH)/Kallmann syndrome (KS). DNAs from (17 male and 31 female) nHH/KS patients were analyzed by targeted next generation sequencing (NGS) of 261 genes involved in hypothalamic, pituitary, and/or olfactory pathways, or suggested by chromosome rearrangements. Selected variants were subjected to Sanger DNA sequencing, the gold standard. The frequency of Sanger-confirmed variants was determined using the ExAC database. Variants were classified as likely pathogenic (frameshift, nonsense, and splice site) or predicted pathogenic (nonsynonymous missense). Two novel FGFR1 mutations were identified, as were 18 new candidate genes including: AMN1, CCKBR, CRY1, CXCR4, FGF13, GAP43, GLI3, JAG1, NOS1, MASTL, NOTCH1, NRP2, PALM2, PDE3A, PLEKHA5, RD3, and TRAPPC9, and TSPAN11. Digenic and trigenic variants were found in 8/48 (16.7%) and 1/48 (2.1%) patients, respectively. NGS with confirmation by Sanger sequencing resulted in the identification of new causative FGFR1 gene mutations and suggested 18 new candidate genes in nHH/KS.

Premature Ovarian Insufficiency: New Perspectives on Genetic Cause and Phenotypic Spectrum

Premature ovarian insufficiency (POI) is one form of female infertility, defined by loss of ovarian activity before the age of 40 and characterized by amenorrhea (primary or secondary) with raised gonadotropins and low estradiol. POI affects up to one in 100 females, including one in 1000 before the age of 30. Substantial evidence suggests a genetic basis for POI; however, the majority of cases remain unexplained, indicating that genes likely to be associated with this condition are yet to be discovered. This review discusses the current knowledge of the genetic basis of POI. We highlight genes typically known to cause syndromic POI that can be responsible for isolated POI. The role of mouse models in understanding POI pathogenesis is discussed, and a thorough list of candidate POI genes is provided. Identifying a genetic basis for POI has multiple advantages, such as enabling the identification of presymptomatic family members who can be offered counseling and cryopreservation of eggs before depletion, enabling personalized treatment based on the cause of an individual's condition, and providing better understanding of disease mechanisms that ultimately aid the development of improved treatments.

Clinical Applications of Gonadotropins in the Male

The pituitary gonadotropins, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) play a pivotal role in reproduction. The synthesis and secretion of gonadotropins are regulated by complex interactions among several endocrine, paracrine, and autocrine factors of diverse chemical structure. In men, LH regulates the synthesis of androgens by the Leydig cells, whereas FSH promotes Sertoli cell function and thereby influences spermatogenesis. Gonadotropins are complex molecules composed of two subunits, the α- and β-subunit, that are noncovalently associated. Gonadotropins are decorated with glycans that regulate several functions of the protein including folding, heterodimerization, stability, transport, conformational maturation, efficiency of heterodimer secretion, metabolic fate, interaction with their cognate receptor, and selective activation of signaling pathways. A number of congenital and acquired abnormalities lead to gonadotropin deficiency and hypogonadotropic hypogonadism, a condition amenable to treatment with exogenous gonadotropins. Several natural and recombinant preparations of gonadotropins are currently available for therapeutic purposes. The difference between natural and the currently available recombinant preparations (which are massively produced in Chinese hamster ovary cells for commercial purposes) mainly lies in the abundance of some of the carbohydrates that conform the complex glycans attached to the protein core. Whereas administration of exogenous gonadotropins in patients with isolated congenital hypogonadotropic hypogonadism is a well recognized therapeutic approach, their role in treating men with normogonadotropic idiopathic infertility is still controversial. This chapter concentrates on the main structural and functional features of the gonadotropin hormones and how basic concepts have been translated into the clinical arena to guide therapy for gonadotropin deficit in males.

Minireview: Insights Into the Structural and Molecular Consequences of the TSH-β Mutation C105Vfs114X

Naturally occurring thyrotropin (TSH) mutations are rare, which is also the case for the homologous heterodimeric glycoprotein hormones (GPHs) follitropin (FSH), lutropin (LH), and choriogonadotropin (CG). Patients with TSH-inactivating mutations present with central congenital hypothyroidism. Here, we summarize insights into the most frequent loss-of-function β-subunit of TSH mutation C105Vfs114X, which is associated with isolated TSH deficiency. This review will address the following question. What is currently known on the molecular background of this TSH variant on a protein level? It has not yet been clarified how C105Vfs114X causes early symptoms in affected patients, which are comparably severe to those observed in newborns lacking any functional thyroid tissue (athyreosis). To better understand the mechanisms of this mutant, we have summarized published reports and complemented this information with a structural perspective on GPHs. By including the ancestral TSH receptor agonist thyrostimulin and pathogenic mutations reported for FSH, LH, and choriogonadotropin in the analysis, insightful structure function and evolutionary restrictions become apparent. However, comparisons of immunogenicity and bioactivity of different GPH variants is hindered by a lack of consensus for functional analysis and the diversity of used GPH assays. Accordingly, relevant gaps of knowledge concerning details of GPH mutation-related effects are identified and highlighted in this review. These issues are of general importance as several previous and recent studies point towards the high impact of GPH variants in differential signaling regulation at GPH receptors (GPHRs), both endogenously and under diseased conditions. Further improvement in this area is of decisive importance for the development of novel targeted therapies.

Genetic analysis of zebrafish gonadotropin (FSH and LH) functions by TALEN-mediated gene disruption

Vertebrate reproduction is controlled by two gonadotropins (FSH and LH) from the pituitary. Despite numerous studies on FSH and LH in fish species, their functions in reproduction still remain poorly defined. This is partly due to the lack of powerful genetic approaches for functional studies in adult fish. This situation is now changing with the emergence of genome-editing technologies, especially Transcription Activator-Like Effector Nuclease (TALEN) and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR). In this study, we deleted the hormone-specific β-genes of both FSH and LH in the zebrafish using TALEN. This was followed by a phenotype analysis for key reproductive events, including gonadal differentiation, puberty onset, gametogenesis, final maturation, and fertility. FSH-deficient zebrafish (fshb(-/-)) were surprisingly fertile in both sexes; however, the development of both the ovary and testis was significantly delayed. In contrast, LH-deficient zebrafish (lhb(-/-)) showed normal gonadal growth, but the females failed to spawn and were therefore infertile. Using previtellogenic follicles as the marker, we observed a significant delay of puberty onset in the fshb mutant but not the lhb mutant females. Interestingly, FSH seemed to play a role in maintaining the female status because we repeatedly observed sexual reversal in the fshb mutant. Neither the fshb nor lhb mutation alone seemed to affect gonadal differentiation; however, the double mutation of the two genes led to all males, although the development of the testis was significantly delayed. In summary, our data confirmed some well-known functions of FSH and LH in fish while also providing evidence for novel functions, which would be difficult to reveal using traditional biochemical and physiological approaches.

Genetic evidence that lower circulating FSH levels lengthen menstrual cycle, increase age at menopause and impact female reproductive health

STUDY QUESTION

How does a genetic variant in the FSHB promoter, known to alter FSH levels, impact female reproductive health?

SUMMARY ANSWER

The T allele of the FSHB promoter polymorphism (rs10835638; c.-211G>T) results in longer menstrual cycles and later menopause and, while having detrimental effects on fertility, is protective against endometriosis.

WHAT IS KNOWN ALREADY

The FSHB promoter polymorphism (rs10835638; c.-211G>T) affects levels of FSHB transcription and, as a result, circulating levels of FSH. FSH is required for normal fertility and genetic variants at the FSHB locus are associated with age at menopause and polycystic ovary syndrome (PCOS).

STUDY DESIGN, SIZE, DURATION

We used cross-sectional data from the UK Biobank to look at associations between the FSHB promoter polymorphism and reproductive traits, and performed a genome-wide association study (GWAS) for length of menstrual cycle.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We included white British individuals aged 40-69 years in 2006-2010, in the May 2015 release of genetic data from UK Biobank. We tested the FSH-lowering T allele of the FSHB promoter polymorphism (rs10835638; c.-211G>T) for associations with 29, mainly female, reproductive phenotypes in up to 63 350 women and 56 608 men. We conducted a GWAS in 9534 individuals to identify genetic variants associated with length of menstrual cycle.

MAIN RESULTS AND THE ROLE OF CHANCE

The FSH-lowering T allele of the FSHB promoter polymorphism (rs10835638; MAF 0.16) was associated with longer menstrual cycles [0.16 SD (c. 1 day) per minor allele; 95% confidence interval (CI) 0.12-0.20; P = 6 × 10(-16)], later age at menopause (0.13 years per minor allele; 95% CI 0.04-0.22; P = 5.7 × 10(-3)), greater female nulliparity [odds ratio (OR) = 1.06; 95% CI 1.02-1.11; P = 4.8 × 10(-3)] and lower risk of endometriosis (OR = 0.79; 95% CI 0.69-0.90; P = 4.1 × 10(-4)). The FSH-lowering T allele was not associated with other female reproductive illnesses or conditions in our study and we did not replicate associations with male infertility or PCOS. In the GWAS for menstrual cycle length, only variants near the FSHB gene reached genome-wide significance (P < 5 × 10(-9)).

LIMITATIONS, REASONS FOR CAUTION

The data included might be affected by recall bias. Cycle length was not available for 25% of women still cycling (1% did not answer, 6% did not know and for 18% cycle length was recorded as 'irregular'). Women with a cycle length recorded were aged over 40 and were approaching menopause; however, we did not find evidence that this affected the results. Many of the groups with illnesses had relatively small sample sizes and so the study may have been under-powered to detect an effect.

WIDER IMPLICATIONS OF THE FINDINGS

We found a strong novel association between a genetic variant that lowers FSH levels and longer menstrual cycles, at a locus previously robustly associated with age at menopause. The variant was also associated with nulliparity and endometriosis risk. These findings should now be verified in a second independent group of patients. We conclude that lifetime differences in circulating levels of FSH between individuals can influence menstrual cycle length and a range of reproductive outcomes, including menopause timing, infertility, endometriosis and PCOS.

STUDY FUNDING/COMPETING INTERESTS

None.

TRIAL REGISTRATION NUMBER

Not applicable.

Molecular insights into the aetiology of female reproductive ageing

As age at pubertal onset declines and age at first pregnancy increases, the mechanisms that regulate female reproductive lifespan become increasingly relevant to population health. The timing of menarche and menopause can have profound effects not only on fertility but also on the risk of diseases such as type 2 diabetes mellitus, cardiovascular disease and breast cancer. Genetic studies have identified dozens of highly penetrant rare mutations associated with reproductive disorders, and also ∼175 common genetic variants associated with the timing of puberty or menopause. These findings, alongside other functional studies, have highlighted a diverse range of mechanisms involved in reproductive ageing, implicating core biological processes such as cell cycle regulation and energy homeostasis. The aim of this article is to review the contribution of such genetic findings to our understanding of the molecular regulation of reproductive timing, as well as the biological basis of the epidemiological links between reproductive ageing and disease risk.

Genetic Regulation of Puberty Timing in Humans

Understanding the regulation of puberty timing has relevance to developmental and human biology and to the pathogenesis of various diseases. Recent large-scale genome-wide association studies on puberty timing and adult height, body mass index (BMI) and central body shape provide evidence for shared biological mechanisms that regulate these traits. There is a substantial genetic overlap between age at menarche in women and BMI, with almost invariable directional consistency with the epidemiological associations between earlier menarche and higher BMI. By contrast, the genetic loci identified for age at menarche are largely distinct from those identified for central body shape, while alleles that confer earlier menarche can be associated with taller or shorter adult height. The findings of population-based studies on age at menarche show increasing relevance for other studies of rare monogenic disorders and enrich our understanding of the mechanisms that regulate the timing of puberty and reproductive function.

Hormonal therapy for non-obstructive azoospermia: basic and clinical perspectives

Microdissection testicular sperm extraction (micro-TESE) combined with intracytoplasmic sperm injection is a standard therapeutic option for patients with non-obstructive azoospermia (NOA). Hormonal treatment has been believed to be ineffective for NOA because of high gonadotropin levels; however, several studies have stimulated spermatogenesis before or after micro-TESE by using anti-estrogens, aromatase inhibitors, and gonadotropins. These results remain controversial; however, it is obvious that some of the patients showed a distinct improvement in sperm retrieval by micro-TESE, and sperm was observed in the ejaculates of a small number of NOA patients. One potential way to improve spermatogenesis is by optimizing the intratesticular testosterone (ITT) levels. ITT has been shown to be increased after hCG-based hormonal therapy. The androgen receptor that is located on Sertoli cells plays a major role in spermatogenesis, and other hormonal and non-hormonal factors may also be involved. Before establishing a new hormonal treatment protocol to stimulate spermatogenesis in NOA patients, further basic investigations regarding the pathophysiology of spermatogenic impairment are needed. Gaining a better understanding of this issue will allow us to tailor a specific treatment for each patient.

Hypogonadotropic hypogonadism: new identification of testicular blood flow and varicocele after treatment with gonadotropins

OBJECTIVE

To investigate testicular changes in patients with hypogonadotropic hypogonadism (HH) after treatment with gonadotropins.

DESIGN

Patients with HH were investigated and followed before and after treatment.

SETTING

Urology and andrology clinic of a teaching hospital.

PATIENT(S)

Consecutive male patients with diagnosed HH.

INTERVENTION(S)

All patients were treated with gonadotropins during the study period and later.

MAIN OUTCOME MEASURE(S)

The hormonal status and scrotal color Doppler ultrasound (CDUS) of patients was recorded before and after treatment.

RESULT(S)

Twenty-six patients with HH (ages 18-43 years) were followed for 8-29 months. After treatment, serum T and secondary sex characters improved in all and spermatogenesis developed in 61.5% of patients. Before treatment, testicular (intraparenchymal blood flow) was undetectable in all and barely detectable in three patients. This improved significantly to 4.53±5.44 and 4.27±4.97 cm/second, respectively, after treatment. Subcapsular arterial flow and testicular size also improved significantly. Similarly, after treatment, transverse epididymal diameter (TED) increased significantly. At baseline, no patient had detectable varicocele on CDUS. After treatment, varicocele was demonstrable in 23% of patients. This finding was further evaluated retrospectively from our 76 HH patient files. None of them had varicocele before treatment, but after treatment 19.73% were found to have varicocele.

CONCLUSION(S)

Patients with HH responded to gonadotropins by improvement in testicular blood flow and increase in TED. In some patients, varicocele was found to develop after treatment.

Follicle-stimulating hormone receptor (FSHR) alternative skipping of exon 2 or 3 affects ovarian response to FSH

Genes critical for fertility are highly conserved in mammals. Interspecies DNA sequence variation, resulting in amino acid substitutions and post-transcriptional modifications, including alternative splicing, are a result of evolution and speciation. The mammalian follicle-stimulating hormone receptor (FSHR) gene encodes distinct species-specific forms by alternative splicing. Skipping of exon 2 of the human FSHR was reported in women of North American origin and correlated with low response to ovarian stimulation with exogenous follicle-stimulating hormone (FSH). To determine whether this variant correlated with low response in women of different genetic backgrounds, we performed a blinded retrospective observational study in a Turkish cohort. Ovarian response was determined as low, intermediate or high according to retrieved oocyte numbers after classifying patients in four age groups (<35, 35-37, 38-40, >40). Cumulus cells collected from 96 women undergoing IVF/ICSI following controlled ovarian hyperstimulation revealed four alternatively spliced FSHR products in seven patients (8%): exon 2 deletion in four patients; exon 3 and exons 2 + 3 deletion in one patient each, and a retention of an intron 1 fragment in one patient. In all others (92%) splicing was intact. Alternative skipping of exons 2, 3 or 2 + 3 were exclusive to low responders and was independent of the use of agonist or antagonist. Interestingly, skipping of exon 3 occurs naturally in the ovaries of domestic cats--a good comparative model for human fertility. We tested the signaling potential of human and cat variants after transfection in HEK293 cells and FSH stimulation. None of the splicing variants initiated cAMP signaling despite high FSH doses, unlike full-length proteins. These data substantiate the occurrence of FSHR exon skipping in a subgroup of low responders and suggest that species-specific regulation of FSHR splicing plays diverse roles in mammalian ovarian function.

Differential expression of nasal embryonic LHRH factor (NELF) variants in immortalized GnRH neuronal cell lines

NELF, a protein identified in migratory GnRH neurons, is predominantly nuclear and alternatively spliced. However, specific NELF splice variants expressed in immortalized GnRH neuronal cell lines from mouse and human are not known. RNA from migratory (GN11 and NLT) and postmigratory (GT1-7) cells in mouse, and (FNCB4-hTERT) cells in human was subjected to RT-PCR. RT-PCR products were cloned, electrophoresed on denaturing gradient gels and sequenced. In addition, quantitative RT-PCR was performed using variant-specific primers. Western blot and immunofluorescence using confocal microscopy were performed for selected variants. Nelf variant 2 (v2), which contains a nuclear localization signal (NLS), was the predominant variant in all mouse and human GnRH neurons. Variants without a NLS (v3 in mouse; v4 in human) were identified. In mouse, v2 protein expression was nuclear, while v3 was non-nuclear. In mouse GnRH neurons, six Nelf splice variant transcripts were identified, including three previously unreported variants. In human, four NELF variant transcripts were observed. In both mouse and human, nuclear and non-nuclear variant transcript and protein were identified, explaining variable NELF cellular localization.

A human FSHB promoter SNP associated with low FSH levels in men impairs LHX3 binding and basal FSHB transcription

FSH production is important for human gametogenesis. In addition to inactivating mutations in the FSHB gene, which result in infertility in both sexes, a G/T single-nucleotide polymorphism (SNP) at -211 relative to the transcription start site of the 5' untranslated region of FSHB has been reported to be associated with reduced serum FSH levels in men. In this study, we sought to identify the potential mechanism by which the -211 SNP reduces FSH levels. Although the SNP resides in a putative hormone response element, we showed that, unlike the murine gene, human FSHB was not induced by androgens or progestins in gonadotropes. On the other hand, we found that the LHX3 homeodomain transcription factor bound to an 11-bp element in the human FSHB promoter that includes the -211 nucleotide. Furthermore, we also demonstrated that LHX3 bound with greater affinity to the wild-type human FSHB promoter compared with the -211 G/T mutation and that LHX3 binding was more effectively competed with excess wild-type oligonucleotide than with the SNP. Finally, we showed that FSHB transcription was decreased in gonadotrope cells with the -211 G/T mutation compared with the wild-type FSHB promoter. Altogether, our results suggest that decreased serum FSH levels in men with the SNP likely result from reduced LHX3 binding and induction of FSHB transcription.

Delayed puberty and estrogen resistance in a woman with estrogen receptor α variant

Although androgen resistance has been characterized in men with a normal chromosome complement and mutations in the androgen-receptor gene, a mutation in the gene encoding estrogen receptor α (ESR1) was previously described only in one man and not, to our knowledge, in a woman. We now describe an 18-year-old woman without breast development and with markedly elevated serum levels of estrogens and bilateral multicystic ovaries. She was found to have a homozygous loss-of-function ESR1 mutation in a completely conserved residue that interferes with estrogen signaling. Her clinical presentation was similar to that in the mouse orthologue knockout. This case shows that disruption of ESR1 causes profound estrogen resistance in women. (Funded by the National Institutes of Health.).