Association of AccI polymorphism in the follicle-stimulating hormone beta gene with polycystic ovary syndrome

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.

Pharmacogenetics of FSH Action in the Female

The purpose of a pharmacogenomic approach is to tailor treatment on the basis of an individual human genotype. This strategy is becoming increasingly common in medicine, and important results have been obtained in oncologic and antimicrobial therapies. The rapid technological developments and availability of innovative methodologies have revealed the existence of numerous genotypes that can influence the action of medications and give rise to the idea that a true "individualized" approach could become in the future a reality in clinical practice. Moreover, compared to the past, genotype analyses are now more easily available at accessible cost. Concerning human reproduction, there is ample evidence that several variants of gonadotropins and their receptors influence female reproductive health and ovarian response to exogenous gonadotropins. In more detail, variants in genes of follicle-stimulating hormone β-chain (FSH-B) and its receptor (FSH-R) seem to be the most promising candidates for a pharmacogenomic approach to controlled ovarian stimulation in assisted reproductive technologies. In the present review, we summarize the evidence regarding FSH-B and FSH-R variants, with special reference to their impact on reproductive health and assisted reproductive technology treatments.

Follicle Stimulating Hormone Receptor (FSHR) Polymorphisms and Polycystic Ovary Syndrome (PCOS)

Polycystic ovary syndrome (PCOS) is the commonest endocrine abnormality in women of reproductive age typically presenting with chronic oligo- or anovulation, clinical, or biochemical hyperandrogenism and polycystic ovarian morphology (PCOM). Restoring mono-ovulation is the ultimate goal of ovulation induction and most women do respond to ovulation inducing agents causing their Follicle-stimulating hormone (FSH) levels to rise. Familial clustering and the results from twin studies strongly support an underlying genetic basis for PCOS. Recent Genome wide association studies (GWAS) have identified several genetic variants being genome wide significantly associated with PCOS. Amongst those are variants in or near the Luteinizing hormone (LH) and FSH receptor genes as well as a variant in the FSH-β gene. The aim of this review is to summarize the available evidence as to whether single nucleotide polymorphisms are able to modify the PCOS phenotype or whether they constitute a risk factor for the syndrome. Data on the role of FSHR polymorphisms in PCOS are conflicting. It seems that in large Chinese studies FSHR polymorphisms are not associated with either PCOS risk or with PCOS treatment outcome. However, in large scale studies in Caucasians these polymorphisms seem to influence the risk of having PCOS. Moreover, these studies also showed that some polymorphisms might affect some clinical features of PCOS as well as treatment outcome. Although most research has focussed on the role of FSHR polymorphisms there seems to be also some evidence showing that single nucleotide polymorphisms (SNPs) in the LHCG-Receptor as well as those in FSH-β gene might also alter the phenotype of PCOS. In conclusion most studies confirm that FSHR polymorphisms do alter the phenotype of PCOS in that they either alter the response to exogenous FSH or hat they increase the risk of having PCOS.

Identification of selected genetic polymorphisms in polycystic ovary syndrome in Sri Lankan women using low cost genotyping techniques

Background

Polycystic ovary syndrome (PCOS), the commonest endocrine disorder affecting young women, appears to be a multigenic trait with contributing genes being unclear. Hence, analysis of polymorphisms in multiple candidate genes is required. Currently available genotyping methods are expensive, time-consuming with limited analytical sensitivity.

Aim

(i) Develop and validate high resolution melting (HRM) assay and allele-specific real-time quantitative PCR (AS-qPCR) for genotyping selected SNPs associated with PCOS.

(ii) Identify selected SNPs and their association with a Sri Lankan cohort of well-characterized PCOS.

Methods

DNA was extracted from women with well-characterized PCOS from adolescence (n = 55) and ethnically matched controls (n = 110). FTO (Fat mass and obesity associated gene; rs9939609), FSHB (Follicle stimulating hormone beta subunit; rs6169), FSHR (Follicle stimulating hormone receptor; rs6165/rs6166), and INSR (Insulin receptor; rs1799817) genes were genotyped using HRM assay. GnRH1 (Gonadotropin releasing hormone; rs6185), LHB (Luteinizing hormone beta subunit; rs1800447/rs34349826) and LHCGR (Luteinizing hormone/choriogonadotropin receptor; rs2293275) genes were genotyped using AS-qPCR method. Genotyping results were validated using Sanger sequencing.

Results

A significant association was observed within FTO gene polymorphism (rs9939609) and PCOS. Genotype frequency of FTO gene (rs9939609)—cases versus controls were TT-36.4% vs.65.4% (p<0.05), AT-23.6% vs.20.9%, AA-40% vs.13.6% (p<0.05). Genotype frequencies of the SNPs GnRH1 (rs6185), FSHB (rs6169), FSHR (rs6165 & rs6166), LHB (rs1800447 & rs34349826), LHCGR (rs2293275) and INSR (rs1799817) were not significantly different between cases and controls (p>0.05). Only the mutant alleles were observed for LHB rs1800447 and rs34349826 SNPs in both groups. The HRM and AS-qPCR assay results had 100% concordance with sequencing results.

Conclusions

FTO gene rs9939609 polymorphism is significantly more prevalent among Sri Lankan PCOS subjects while the other selected SNPs of HPG axis genes and INSR gene showed no association. HRM and AS-qPCR assays provide a reliable, fast and user-friendly genotyping method facilitating wider implication in clinical practice.

Pharmacogenetics of follicle-stimulating hormone action

PURPOSE OF REVIEW

To review the current knowledge of genetic variants in the two genes affecting the individual responsiveness to follicle-stimulating hormone (FSH) action-the FSH beta-subunit (FSHB) and the FSH receptor (FSHR), as well as the pharmacogenetic ramifications of the findings.

RECENT FINDINGS

Four common variants in the FSHB and the FSHR genes were shown to exhibit significant effect on FSH action: linked FSHR variants Thr307Ala and Asn680Ser determining common receptor isoforms, and gene expression affecting polymorphisms FSHR -29G/A and FSHB -211G/T. In women, the FSHR Thr307Ala/Asn680Ser polymorphisms show consistent predictive value for estimating the most optimal recombinant FSH dosage in controlled ovarian hyperstimulation (COH). The same variants exhibit a potential for the pharmacogenetic assessment of the treatment of polycystic ovarian syndrome. The FSHR -29G/A variant was also shown to contribute to ovarian response to COH. Pilot studies have suggested the FSHB -211 TT homozygous oligozoospermic men with genetically determined low concentration of FSH, as potentially the best responders to FSH treatment; furthermore, modulation of this response by FSHR polymorphisms is possible.

SUMMARY

Genetic variants in FSHB and FSHR exhibit a potential for pharmacogenetic applications in selecting appropriate treatment options (timing and dosage) in male and female conditions requiring or benefiting from FSH therapy.

Effects of polymorphisms in gonadotropin and gonadotropin receptor genes on reproductive function

Gonadotropins, the action of which is mediated at the level of their gonadal receptors, play a key role in sexual development, reproductive functions and in metabolism. The involvement of the gonadotropins and their receptor genotypes on reproductive function are widely studied. A large number of gonadotropins and their receptors gene polymorphisms are known, but the only one considerable as a clear, absolute genetic marker of reproductive features or disfunctions is the FSHR Asn680Ser polymorphism, since it modulates ovarian response to FSH. The aim of these studies would to be the prediction of the genetic causes of sex-related diseases to enable a customized clinical setting based on individual response of patients undergoing gonadotropin stimulation. In this review we discuss the latest information about the effects of polymorphisms of the gonadotropins and their receptor genes on reproductive functions of both male and female, and discuss their patho-physiological implications.

Genomics and genetics of gonadotropin beta-subunit genes: Unique FSHB and duplicated LHB/CGB loci

The follicle stimulating hormone (FSH), luteinizing hormone (LH) and chorionic gonadotropin (HCG) play a critical role in human reproduction. Despite the common evolutionary ancestry and functional relatedness of the gonadotropin hormone beta (GtHB) genes, the single-copy FSHB (at 11p13) and the multi-copy LHB/CGB genes (at 19q13.32) exhibit locus-specific differences regarding their genomic context, evolution, genetic variation and expressional profile. FSHB represents a conservative vertebrate gene with a unique function and it is located in a structurally stable gene-poor region. In contrast, the primate-specific LHB/CGB gene cluster is located in a gene-rich genomic context and demonstrates an example of evolutionary young and unstable genomic region. The gene cluster is shaped by a constant balance between selection that acts on specific functions of the loci and frequent gene conversion events among duplicons. As the transcription of the GtHB genes is rate-limiting in the assembly of respective hormones, the genomic and genetic context of the FSHB and the LHB/CGB genes largely affects the profile of the hormone production.

Functional genetic polymorphisms and female reproductive disorders: Part I: Polycystic ovary syndrome and ovarian response

BACKGROUND

The identification of polymorphisms associated with a disease can help to elucidate its pathogenesis, and this knowledge can be used to improve prognosis for women with a particular disorder, such as polycystic ovary syndrome (PCOS). Since an altered response to ovarian stimulation is also a characteristic of the disease, further knowledge about its aetiology could help in defining the parameters that determine the response of an individual to ovarian stimulation.

METHODS

PubMed and EMBASE databases were systematically searched for gene association studies published until the end of August 2007, using search criteria relevant to PCOS and ovarian response to stimulation. Data from additional papers identified through hand searches were also included; 139 publications were reviewed.

RESULTS

Several genes involved in ovarian function and metabolism are associated with increased susceptibility to PCOS, but none is strong enough to correlate alone with susceptibility to the disease, or response to therapy. A single-nucleotide polymorphism in exon 10 of the FSH receptor (FSHR) gene, FSHR p.N680S, was consistently identified as having a significant association with ovarian response to FSH.

CONCLUSIONS

No consistent association between gene polymorphism and PCOS could be identified. The FSHR gene may play a significant role in the success of ovarian stimulation, and can be used as a marker to predict differences in FSHR function and ovarian response to FSH. Genotyping the FSHR p.N680S polymorphism may provide a means of identifying a population of poor responders before in vitro fertilization procedures are initiated.

Genetics of polycystic ovarian syndrome

Polycystic ovarian syndrome is a complex disorder with multiple factors affecting its etiology. Elucidation of specific genes and mode of inheritance remains a significant challenge. Linkage and association studies have resulted in over 50 candidate genes as a source of heritable predisposition; however, small sample sizes and failure to reproduce results have hindered efforts. In addition, low fecundity, lack of a male phenotype, and variation of diagnostic criteria represent unique challenges to discovery of polycystic ovarian syndrome genes. A concerted effort will be necessary to conclusively rule in or rule out candidate genes.

Genomic variants in polycystic ovary syndrome

The polycystic ovary syndrome (PCOS) is a common disorder in premenopausal women, characterized by the presence, among other traits, of hyperandrogenism, insulin resistance, and hyperinsulinism. The familial aggregation of PCOS lead the interest to the molecular genetic basis of this syndrome, especially to the genes encoding proteins involved in androgen synthesis and the regulation of insulin synthesis and action. Considering the relationship between insulin resistance and chronic inflammation, and the clustering of inflammatory markers in PCOS patients, recent studies focused on the involvement of proinflammatory genotypes on the pathogenesis of PCOS. Mounting evidence suggest at present a complex model of inheritance for PCOS, in which predisposing and protecting genomic variants interact with environmental factors such as obesity and a sedentary lifestyle, finally leading to the classic phenotype of this syndrome. Moreover, the association of hyperandrogenism, insulin resistance and chronic inflammation raised the possibility of an increase risk of cardiovascular disease in women suffering from PCOS. In the present review we will summarize the most important findings published to date regarding the molecular genetic mechanisms underlying the association of PCOS with insulin resistance and chronic inflammation, and the possible interaction of these mechanisms with environmental factors.

Human FSH beta subunit gene is highly conserved

FSH is a pituitary gonadotropin that along with LH plays a key role in the regulation of gonadal function. The gonadotropic hormones are composed of two subunits, the common alpha subunit and the hormone-specific beta subunit, which determines the binding to specific receptors and induction of biological response. Unlike the LHbeta gene, shown in earlier studies to harbour several amino acid-altering polymorphisms and mutations, information about the eventual sequence variation of the human FSHbeta subunit is not available. In this study, we made sequence analysis and comparison of polymorphisms found in FSHbeta in two Caucasian populations, the Finns and the Danes. It was found that FSHbeta subunit is highly conserved in these populations. Compared with the published sequences, only three silent polymorphisms were detected in the coding regions of the gene, and the promoter sequence was completely identical with the reported sequence. Two of the polymorphisms found were novel, one in the Finnish and one in the Danish population. The results of the sequence analysis show that the human FSHbeta gene is highly conserved and amino acid changing mutations are apparently extremely rare, at least in the samples collected randomly from control populations. This may be due to the crucial role of normal FSH function in the regulation of fertility.

The molecular-genetic basis of functional hyperandrogenism and the polycystic ovary syndrome

The genetic mechanisms underlying functional hyperandrogenism and the polycystic ovary syndrome (PCOS) remain largely unknown. Given the large number of genetic variants found in association with these disorders, the emerging picture is that of a complex multigenic trait in which environmental influences play an important role in the expression of the hyperandrogenic phenotype. Among others, genomic variants in genes related to the regulation of androgen biosynthesis and function, insulin resistance, and the metabolic syndrome, and proinflammatory genotypes may be involved in the genetic predisposition to functional hyperandrogenism and PCOS. The elucidation of the molecular genetic basis of these disorders has been burdened by the heterogeneity in the diagnostic criteria used to define PCOS, the limited sample size of the studies conducted to date, and the lack of precision in the identification of ethnic and environmental factors that trigger the development of hyperandrogenic disorders. Progress in this area requires adequately sized multicenter collaborative studies after standardization of the diagnostic criteria used to classify hyperandrogenic patients, in whom modifying environmental factors such as ethnicity, diet, and lifestyle are identified with precision. In addition to classic molecular genetic techniques such as linkage analysis in the form of a whole-genome scan and large case-control studies, promising genomic and proteomic approaches will be paramount to our understanding of the pathogenesis of functional hyperandrogenism and PCOS, allowing a more precise prevention, diagnosis, and treatment of these prevalent disorders.

Le syndrome des ovaires polykystiques en période péri-pubertaire : polymorphisme clinique, biologique, métabolique et génétique

Polycystic ovary syndrome (PCOS) is a common cause of hyperandrogenism in adolescent girls. In its complete post menarchal expression, the syndrome is characterized by the association of typical clinical, biological, and ultrasonographic findings. Many factors have contributed to our knowledge of different clinical forms of PCOS in adolescent girls. They are helpful for clarifying misleading situations in a period of life when diagnosis of PCOS implies a treatment for many years and may interfere with gynecological outcome. During the last 3 years, we had the opportunity to manage in our unit 45 adolescent girls with ovarian hyperandrogenism: 32 of them had PCOS and the other 13 functional ovarian hyperandrogenism defined by clinical and biological hyperandrogenism without ultrasonographic abnormality. In this review, we report, from our personal experience as well as from recent literature data, the different clinical expressions of PCOS in the pubertal period: the classical post menarchal form, the exceptional pre menarchal form, the post precocious pubarche and the post precocious puberty forms, the familial expression as well as the dominant metabolic expression.

Relationship between insulin resistance and gonadotropin dissociation in obese and nonobese women with polycystic ovary syndrome

OBJECTIVE

To test the interdependence between insulin resistance (IR) and gonadotropin dissociation (GD) in polycystic ovary syndrome (PCOS).

DESIGN

Cross-sectional prospective study.

SETTING

Clinical research center.

PATIENT(S)

Thirty-two PCOS patients aged 19-34 years; 16 obese (BMI > or = 27) and 16 nonobese (BMI < 27).

INTERVENTION(S)

A 75-g oral glucose tolerance test (OGTT) and a 100-microg i.v. GnRH test were performed on different days. Blood was taken at 0, 30, 60, 90, 120, and 180 minutes in each test. Serum glucose, insulin, LH, and FSH were measured.

MAIN OUTCOME MEASURE(S)

Area under the curve was calculated for glucose, insulin, and glucose-to-insulin ratio (GIR), and for LH, FSH, and LH-FSH ratio.

RESULT(S)

Glucose, insulin, and GIR were not modified significantly during the GnRH test, nor LH, FSH and LH-FSH ratio throughout the OGTT. There were no significant differences in GIR response of patients with and without GD, nor in LH-FSH ratio of patients with and without IR, after OGTT and GnRH test. However, obese patients with IR had a significantly larger (P<.04) area under the curve for LH-FSH ratio than those without IR after GnRH test, but not after OGTT test.

CONCLUSION(S)

Insulin resistance and GD do not appear to be related events in PCOS, suggesting that each one might be determined by different genetic disorders. However, IR can affect GD after chronic stimulation in obese patients.

The polycystic ovary syndrome: what does insulin resistance have to do with it?

About half of infertility cases are attributable to female factors, of which anovulation is the leading cause. Most cases of anovulation are due to the polycystic ovarian syndrome (PCOS). Clinically PCOS, present in 5% of all women, consists of anovulation, acne, hirsutism, reversed LH-to-FSH ratio and often resistance to insulin. In some cases PCOS appears in familial clusters but its genetic cause is unknown. Several genes were suggested as possible culprits for PCOS but their involvement has not been proven. The central paradox regarding the role of insulin in PCOS is the high responsiveness to insulin by the ovary, as opposed to the resistance of the whole body. On the backdrop of knowledge of several paralogous genes for each of the participating proteins in the insulin signal transduction pathways, it is possible that different paralogues propagate the intracellular signal in the ovary as opposed to peripheral tissues. Studies by microarray techniques of the different gene expression profiles in the two ovarian cells and peripheral cells such as adipocytes could clarify whether the ovarian defect in PCOS is identical to the peripheral defect in insulin signal transduction, or whether serum insulin concentrations simply serve to reveal the ovarian defect.

Molecular progress in infertility: polycystic ovary syndrome

OBJECTIVE

To review the evidence that polycystic ovary syndrome is a genetic disease.

DESIGN

Review of published literature.

RESULTS

The existing literature provides a strong basis for arguing that PCOS clusters in families. However, the mode of inheritance of the disorder is still uncertain, although the majority of studies are consistent with an autosomal dominant pattern, modified perhaps by environmental factors. In addition, studies on PCOS cells (theca, muscle, and adipocytes) in culture have documented a persistent biochemical and molecular phenotype that distinguishes them from normal cells. Although several loci have been proposed as PCOS genes including CYP11A, the insulin gene, and a region near the insulin receptor, the evidence supporting linkage is not overwhelming. The strongest case can be made for the region near the insulin receptor gene, as it has been identified in two separate studies. However, the responsible gene at chromosome 19p13.3 remains to be identified. Association studies have provided a number of potential loci with genetic variants that may create or add to a PCOS phenotype, including Calpain 10, IRS-1 and -2, and SHBG.

CONCLUSIONS

Collectively, these findings are consistent with the concept that a gene or several genes are linked to PCOS susceptibility. Because the mutations/genotypes associated with PCOS are rare, and their full impact on the phenotype incompletely understood, routine screening of women with PCOS or stigmata of PCOS for these genetic variants is not indicated at this time. Currently the treatment implications for individually identified genetic variants is uncertain and must be addressed on a case by case basis.

[Polycystic ovary syndrome: recent genetic contributions]

Polycystic ovary syndrome is the most common endocrine disorder in women of reproductive age. It is characterized by hyperandrogenism, chronic anovulation and it is often associated with hyperinsulinemia, insulin resistance and dyslipidaemia. The pathophysiology of polycystic ovary syndrome seems to implicate primary defects in ovarian steroidogenesis, influenced by environment, insulin action and obesity. Polycystic ovary syndrome is probably both a multigenetic and environmental disease. Knowing the genes of polycystic ovary syndrome would be helpful to develop therapeutics and prevention. Genes of gonadotrophins, steroid hormone synthesis and insulin resistance seem not to be directly involved, except perhaps the CYP 11 a gene. On the other hand, identification of the signal transduction pathways involved in these genes may provide valuable information that can be applied to other clinical manifestations of polycystic ovary syndrome (follicular growth arrest, insulin resistance, obesity and endometrial cancer...).