NOBOX homeobox mutation causes premature ovarian failure

The Genetics of Non-Syndromic Primary Ovarian Insufficiency: A Systematic Review

Several causes for primary ovarian insufficiency (POI) have been described, including iatrogenic and environmental factor, viral infections, chronic disease as well as genetic alterations. The aim of this review was to collect all the ge- netic mutations associated with non-syndromic POI. All studies, including gene screening, genome-wide study and as- sessing genetic mutations associated with POI, were included and analyzed in this systematic review. Syndromic POI and chromosomal abnormalities were not evaluated. Single gene perturbations, including genes on the X chromosome (such as BMP15, PGRMC1 and FMR1) and genes on autosomal chromosomes (such as GDF9, FIGLA, NOBOX, ESR1, FSHR and NANOS3) have a positive correlation with non-syndromic POI. Future strategies include linkage analysis of families with multiple affected members, array comparative genomic hybridization (CGH) for analysis of copy number variations, next generation sequencing technology and genome-wide data analysis. This review showed variability of the genetic factors associated with POI. These findings may help future genetic screening studies on large cohort of women.

Mutational analysis of theFAM175A gene in patients with premature ovarian insufficiency

RESEARCH QUESTION

The family with sequence similarity 175 member A gene (FAM175A; also known as ABRAXAS1, CCDC98 and ABRA1), a member of the DNA repair family, contributes to the BRCA1 (BRCA1 DNA repair associated)-dependent DNA damage response and is associated with age at natural menopause. However, it remains poorly understood whether sequence variants in FAM175A are causative for premature ovarian insufficiency (POI). The aim of this study was to investigate whether mutations in the gene FAM175A were present in patients with POI.

DESIGN

A total of 400 women with idiopathic POI and 498 control women with regular menstruation (306 age-matched women and 192 women over 40 years old) were recruited. After Sanger sequencing of FAM175A, functional experiments were carried out to explore the deleterious effects of the identified variation. DNA damage was subsequently induced by mitomycin C (MMC), and DNA repair capacity and G2-M checkpoint activation were evaluated by examining the phosphorylation level of H2AX (H2A histone family, member X) and the percentage of mitotic cells, respectively.

RESULTS

One rare single-nucleotide polymorphism, rs755187051 in gene FAM175A, c.C727G (p.L243V), was identified in two patients but absent in the 498 controls. The functional experiments demonstrated that overexpression of variant p.L243V in HeLa cells resulted in a similar sensitivity to MMC-induced damage compared with cells transfected with wild-type FAM175A. Moreover, after treatment with MMC, there were no differences in DNA repair capacity and G2-M checkpoint activation between the mutant and wild-type genes.

CONCLUSION

Our results suggest that the p.L243V variant of FAM175A may not be causative for POI. The contribution of FAM175A to POI needs further exploration.

Mutations in the mitochondrial ribosomal protein MRPS22 lead to primary ovarian insufficiency

Primary ovarian insufficiency (POI) is characterized by amenorrhea and loss or dysfunction of ovarian follicles prior to the age of 40. POI has been associated with autosomal recessive mutations in genes involving hormonal signaling and folliculogenesis, however, the genetic etiology of POI most often remains unknown. Here we report MRPS22 homozygous missense variants c.404G>A (p.R135Q) and c.605G>A (p.R202H) identified in four females from two independent consanguineous families as a novel genetic cause of POI in adolescents. Both missense mutations identified in MRPS22 are rare, occurred in highly evolutionarily conserved residues, and are predicted to be deleterious to protein function. In contrast to prior reports of mutations in MRPS22 associated with severe mitochondrial disease, the POI phenotype is far less severe. Consistent with this genotype-phenotype correlation, mitochondrial defects in oxidative phosphorylation or rRNA levels were not detected in fibroblasts derived from the POI patients, suggesting a non-bioenergetic or tissue-specific mitochondrial defect. Furthermore, we demonstrate in a Drosophila model that mRpS22 deficiency specifically in somatic cells of the ovary had no effect on fertility, whereas flies with mRpS22 deficiency specifically in germ cells were infertile and agametic, demonstrating a cell autonomous requirement for mRpS22 in germ cell development. These findings collectively identify that MRPS22, a component of the small mitochondrial ribosome subunit, is critical for ovarian development and may therefore provide insight into the pathophysiology and treatment of ovarian dysfunction.

Genetics of Female Infertility: Molecular Study of Newborn Ovary Homeobox Gene in Poor Ovarian Responders

Background

Newborn ovary homeobox (NOBOX) gene plays a critical role in the transcriptional regulation of oocyte-specific genes. Previous studies have demonstrated a pathogenic effect of NOBOX variants on premature ovarian insufficiency (POI) patients. Poor ovarian response (POR) is a risk factor for POI. Therefore, genetic variants in the NOBOX gene may also be studied as risk factors for POR development.

Aims

The aim of the study is to investigate the association between seven known NOBOX single-nucleotide polymorphisms (SNPs) and POR in Jordanian females.

Settings and Design

This was a case-control study of 60 females with POR for controlled ovarian hyperstimulation and 59 healthy females with no history of reproductive problems. Blood samples were collected from the participants and seven SNPs of NOBOX gene were screened.

Subjects and Methods

DNA was extracted from blood samples. Polymerase chain reaction with primers specific for seven known SNPs in NOBOX gene was used to amplify the specified region within the gene followed by Sanger sequencing.

Results

The seven SNPs investigated in this study, namely, rs77587352 (c.271G>T, p. Gly91Trp), rs7800847 (c.349C>T, p. Arg117Trp), rs193303102 (c.907C>T, p. Arg303X), rs193303103 (c.1025G>C, p. Ser342Thr), rs193303104 (c.1048G>T, p. Val350Leu), rs201947677 (c.1064G>A, p. Arg355His), and rs146227301 (c.1856C>T, p. Pro619Leu), only represent the wild-type allele in both females with POR and healthy participants.

Conclusions

The results show that only monomorphic genotype of the NOBOX variants was found in Jordanian females studied.

Connecting links between genetic factors defining ovarian reserve and recurrent miscarriages

PURPOSE

Approximately 1-2% of the women faces three or more successive spontaneous miscarriages termed as recurrent miscarriage (RM). Many clinical factors have been attributed so far to be the potential risk factors in RM, including uterine anomalies, antiphospholipid syndrome, endocrinological abnormalities, chromosomal abnormalities, and infections. However, in spite of extensive studies, reviews, and array of causes known to be associated with RM, about 50% cases encountered by treating physicians remains unknown. The aims of this study were to evaluate recent publications and to explore oocyte-specific genetic factors that may have role in incidence of recurrent miscarriages.

METHOD

Recent studies have identified common molecular factors contributing both in establishment of ovarian reserve and in early embryonic development. Also, studies have pointed out the relationship between the age-associated depletion of OR and increase in the risk of miscarriages, thus suggestive of an interacting biology. Here, we have gathered literature evidences in establishing connecting links between genetic factors associated with age induced or pathological OR depletion and idiopathic RM, which are the two extreme ends of female reproductive pathology.

CONCLUSION

In light of connecting etiological link between infertility and RM as reviewed in this study, interrogating the oocyte-specific genes with suspected roles in reproductive biology, in cases of unexplained RM, may open new possibilities in widening our understanding of RM pathophysiology.

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

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

Wdr62 is involved in female meiotic initiation via activating JNK signaling and associated with POI in humans

Meiosis is a germ cell-specific division that is indispensable for the generation of haploid gametes. However, the regulatory mechanisms of meiotic initiation remain elusive. Here, we report that the Wdr62 (WD40-repeat protein 62) is involved in meiotic initiation as a permissive factor rather than an instructive factor. Knock-out of this gene in a mouse model resulted in female meiotic initiation defects. Further studies demonstrated that Wdr62 is required for RA-induced Stra8 expression via the activation of JNK signaling, and the defects in meiotic initiation from Wdr62-deficient female mice could be partially rescued by JNK1 overexpression in germ cells. More importantly, two novel mutations of the WDR62 gene were detected in patients with premature ovarian insufficiency (POI), and these mutations played dominant-negative roles in regulating Stra8 expression. Hence, this study revealed that Wdr62 is involved in female meiotic initiation via activating JNK signaling, which displays a novel mechanism for regulating meiotic initiation, and mutation of WDR62 is one of the potential etiologies of POI in humans.

Identification of the first homozygous POLG mutation causing non-syndromic ovarian dysfunction

OBJECTIVE

To investigate the genetic cause of non-syndromic ovarian dysfunction in a patient from a consanguineous family.

METHODS

This study examined a patient with irregular menstrual cycles and abnormal oocytes. The patient had undergone irregular hormone replacement therapy over 3 years to adjust the menstrual cycle and improve ovarian function. Prior to ovarian stimulation in our hospital, 3 months of androgen and regular hormone therapy were used as an intervention method. No follicular development was detected in the subsequent three cycles using letrozole treatment. The patient then received a constantly adjusted dose of menotropins, but produced only one oocyte.

RESULTS

Whole-exome sequencing analysis identified the first homozygous POLG mutation (c.2890C > T; p.R964C) associated with ovarian dysfunction. Sanger sequencing was used to validate. In silico analysis suggested that the p.R964C mutation was pathogenic. Conservation analysis demonstrated that R964 was an important site for the DNA polymerase function of POLG.

CONCLUSIONS

Biallelic mutations in POLG may be associated with ovarian dysfunction. This study has improved our understanding of POLG-related genetic mutations in ovarian dysfunction, and the mode of inheritance of certain sequence variants. This information will assist genetic counseling and precision medicine in the future.

Primary ovarian insufficiency associated with autosomal abnormalities: from chromosome to genome-wide and beyond

OBJECTIVE

The pathophysiology of primary ovarian insufficiency (POI) is not well elucidated. Many candidate genetic aberrations are on the X-chromosome; on the contrary, many genetic perturbations are also on the autosomes. The aim of this review is to summarize the knowledge of genetic aberrations on autosomes from chromosomal rearrangement, gene abnormality, genome-wide association studies and epigenetics.

METHODS

Searches of electronic databases were performed. Articles and abstracts relevant to POI and genetic studies associated with autosomes were summarized in this interpretive literature review.

RESULTS

Various genetic aberrations located on the autosomes were found. These abnormalities are from chromosomal rearrangement, which might disrupt the critical region on chromosome loci or disturbance of the meiosis process. Specific gene aberrations are also identified. The genes that have functions in ovarian development, folliculogenesis, and steroidogenesis on autosomes are proposed to be involved from gene association studies. Gene-to-gene interaction or epistasis also might play a role in POI occurrence. Recently, genetic techniques to study the whole genome have emerged. Although no specific conclusion has been made, the studies using genome-wide association to find the specific aberration throughout the genome in POI have been published. Epigenetic mechanisms might also take part in the pathogenesis of POI.

CONCLUSIONS

The considerably complex process of POI is still not well understood. Further research is needed for gene functional validation studies to confirm the contribution of genes in POI, or additional genome-wide association studies using novel clustered regularly interspaced short palindromic repeat/Cas9 technique might make these mechanisms more comprehensible.

The importance of DNA repair for maintaining oocyte quality in response to anti-cancer treatments, environmental toxins and maternal ageing

BACKGROUND

Within the ovary, oocytes are stored in long-lived structures called primordial follicles, each comprising a meiotically arrested oocyte, surrounded by somatic granulosa cells. It is essential that their genetic integrity is maintained throughout life to ensure that high quality oocytes are available for ovulation. Of all the possible types of DNA damage, DNA double-strand breaks (DSBs) are considered to be the most severe. Recent studies have shown that DNA DSBs can accumulate in oocytes in primordial follicles during reproductive ageing, and are readily induced by exogenous factors such as γ-irradiation, chemotherapy and environmental toxicants. DSBs can induce oocyte death or, alternatively, activate a program of DNA repair in order to restore genetic integrity and promote survival. The repair of DSBs has been intensively studied in the context of meiotic recombination, and in recent years more detail is becoming available regarding the repair capabilities of primordial follicle oocytes.

OBJECTIVE AND RATIONALE

This review discusses the induction and repair of DNA DSBs in primordial follicle oocytes.

SEARCH METHODS

PubMed (Medline) and Google Scholar searches were performed using the key words: primordial follicle oocyte, DNA repair, double-strand break, DNA damage, chemotherapy, radiotherapy, ageing, environmental toxicant. The literature was restricted to papers in the English language and limited to reports in animals and humans dated from 1964 until 2017. The references within these articles were also manually searched.

OUTCOMES

Recent experiments in animal models and humans have provided compelling evidence that primordial follicle oocytes can efficiently repair DNA DSBs arising from diverse origins, but this capacity may decline with increasing age.

WIDER IMPLICATIONS

Primordial follicle oocytes are vulnerable to DNA DSBs emanating from endogenous and exogenous sources. The ability to repair this damage is essential for female fertility. In the long term, augmenting DNA repair in primordial follicle oocytes has implications for the development of novel fertility preservation agents for female cancer patients and for the management of maternal ageing. However, further work is required to fully characterize the specific proteins involved and to develop strategies to bolster their activity.

The molecular complexity of primary ovarian insufficiency aetiology and the use of massively parallel sequencing

Primary ovarian insufficiency (POI) is a frequently occurring pathology, leading to infertility. Genetic anomalies have been described in POI and mutations in numerous genes have been definitively related to the pathogenesis of the disease. Some studies based on next generation sequencing (NGS) have been successfully undertaken as they have led to identify new mutations associated with POI aetiology. The purpose of this review is to present the most relevant molecules involved in diverse complex pathways, which may contribute towards POI. The main genes participating in bipotential gonad formation, sex determination, meiosis, folliculogenesis and ovulation are described to enable understanding how they may be considered putative candidates involved in POI. Considerations regarding NGS technical aspects such as design and data interpretation are mentioned. Successful NGS initiatives used for POI studying and future challenges are also discussed.

A novel homozygous 1-bp deletion in the NOBOX gene in two Brazilian sisters with primary ovarian failure

PURPOSE

Primary ovarian failure (POF) is characterized by amenorrhea, hypoestrogenism, and elevated gonadotropin levels in women leading to infertility under the age of 40 years. POF is a heterogeneous disease with different causes, and several genes have been associated with the POF phenotype. Thus, Whole-exome sequencing (WES) was performed in a consanguineous family with two sisters affected by POF.

METHODS

All exons of both sisters were massively sequenced by WES, and the segregation was confirmed by Sanger sequencing.

RESULTS

The novel homozygous c.1489delT variant in the NOBOX gene was identified in the two sisters with POF. Their parents were heterozygous carriers of this variant and, therefore, consistent with an autosomal recessive mode of inheritance. The c.1489delT NOBOX variant has not been previously reported in any public available databases (1000Genomes, 6500ESP/EVS, ExAC, and gnomAD). Furthermore, this variant was neither present in 387 Brazilian exomes control individuals nor in 200 fertile Brazilian women screened by Sanger sequencing.

CONCLUSION

We report the first familial case of a novel homozygous NOBOX variant with an autosomal recessive mode of inheritance, thus allowing for a genetic diagnosis of primary ovarian failure.

Premature Ovarian Insufficiency - an update on recent advances in understanding and management

Premature ovarian insufficiency is a complex and relatively poorly understood entity with a myriad of etiologies and multisystem sequelae that stem from premature deprivation of ovarian sex hormones. Timely diagnosis with a clear understanding of the various comorbidities that can arise from estrogen deficiency is vital to appropriately counsel and treat these patients. Prompt initiation of hormone therapy is critical to control the unsolicited menopausal symptoms that many women experience and to prevent long-term health complications. Despite ongoing efforts at improving our understanding of the mechanisms involved, any advancement in the field in recent decades has been modest at best and researchers remain thwarted by the complexity and heterogeneity of the underpinnings of this entity. In contrast, the practice of clinical medicine has made meaningful strides in providing assurance to the women with premature ovarian insufficiency that their quality of life as well as long-term health can be optimized through timely intervention. Ongoing research is clearly needed to allow pre-emptive identification of the at-risk population and to identify mechanisms that if addressed in a timely manner, can prolong ovarian function and physiology.

Observation of the influences of diosgenin on aging ovarian reserve and function in a mouse model

BACKGROUND

The aim of this study was to investigate the impact of diosgenin, an important monomer of sapogenins in yams, on ovarian reserve in a natural aging mice model.

STUDY DESIGN

This randomized controlled trial included 60 9-month-old C57 naturally aging female mice. Twenty-one mice were assigned to the dio group and were fed a single dose of diosgenin (200 mg/kg/day) suspended in 0.3% CMC. Twenty mice were assigned to the DHEA group and were fed a single dose of DHEA (1.25 mg/kg/day) suspended in 0.3% CMC. The remaining 20 mice were assigned to the old control group and were fed a single dose of 0.3% CMC. Three months later, the reproductive performance of these female mice was determined by evaluating ovarian follicles and oocyte number and quality in IVF and comparing age-matched and young controls. The impact of NOBOX, GDF9 and BMP15 mRNA expression was also evaluated.

RESULTS

Diosgenin improves ovarian reserve in naturally aging mice in terms of increasing the number of primary follicles (P < 0.05) and serum levels of AMH (P < 0.05).

CONCLUSIONS

Diosgenin could counteract age-associated ovarian dysfunction by improving the ovarian reserve in a natural aging mice model.

Primary ovarian insufficiency in classic galactosemia: current understanding and future research opportunities

Classic galactosemia is an inborn error of the metabolism with devastating consequences. Newborn screening has been successful in markedly reducing the acute neonatal symptoms from this disorder. The dramatic response to dietary treatment is one of the major success stories of newborn screening. However, as children with galactosemia achieve adulthood, they face long-term complications. A majority of women with classic galactosemia develop primary ovarian insufficiency and resulting morbidity. The underlying pathophysiology of this complication is not clear. This review focuses on the reproductive issues seen in girls and women with classic galactosemia. Literature on the effects of classic galactosemia on the female reproductive system was reviewed by an extensive Pubmed search (publications from January 1975 to January 2017) using the keywords: galactosemia, ovarian function/dysfunction, primary ovarian insufficiency/failure, FSH, oxidative stress, fertility preservation. In addition, articles cited in the search articles and literature known to the authors was also included in the review. Our understanding of the role of galactose metabolism in the ovary is limited and the pathogenic mechanisms involved in causing primary ovarian insufficiency are unclear. The relative rarity of galactosemia makes it difficult to accumulate data to determine factors defining timing of ovarian dysfunction or treatment/fertility preservation options for this group of women. In this review, we present reproductive challenges faced by women with classic galactosemia, highlight the gaps in our understanding of mechanisms leading to primary ovarian insufficiency in this population, discuss new advances in fertility preservation options, and recommend collaboration between reproductive medicine and metabolic specialists to improve fertility in these women.

Single nucleotide polymorphisms at miR-146a/196a2 and their primary ovarian insufficiency-related target gene regulation in granulosa cells

MicroRNAs post-transcriptionally regulate gene expression in animals and plants. The aim of this study was to identify new target genes for microRNA polymorphisms (miR-146aC>G and miR-196a2T>C) in primary ovarian insufficiency (POI). We cloned and transfected miR-146aC>G and miR-196a2T>C into human granulosa cells and used microarrays and qPCR-arrays to examine the changes in the messenger RNA expression profile. We show miR-146aC>G and miR-196a2T>C change the mRNA expression patterns in granulosa cell. In each case, mRNAs were up or down-regulated after treatments with miR-146a C or G and miR-196a2 T or C. We found that miR-146a led to a significantly altered regulation of the mRNA levels of FOXO3, FOXL2 and CCND2 compared to controls. We also found that the polymorphisms of miR-146a led to a significantly altered regulation of CCND2 and FOXO3. Our results suggest that miR-146aC>G and miR-196a2T>C can regulate the levels of many of their target transcripts. In addition, specific target genes of miR-146aC>G polymorphisms may be involved in granulosa cell regulation.

Association of miR-938G>A Polymorphisms with Primary Ovarian Insufficiency (POI)-Related Gene Expression

MicroRNAs (miRNAs) post-transcriptionally regulate gene expression in animals and plants. The aim of this study was to investigate whether polymorphisms in miR-938 are associated with the risk of primary ovarian insufficiency (POI) and POI-related target gene regulation. We identified the miR-938G>A polymorphisms within the seed sequence of mature miRNA and aligned the seed sequence with the 3′ untranslated region (UTR) of the gonadotropin-releasing hormone receptor (GnRHR) mRNA, a miR-938 target gene. We found that the binding of miR-938 to the 3′-UTR of GnRHR mRNA was significantly different between normal and variant alleles. Our data suggests that the dysregulation of miR-938G>A influences the binding to GnRHR and that miR-938G>A polymorphisms might contribute to regulation of POI-related target genes.

Role of microRNAs in premature ovarian insufficiency

Premature ovarian insufficiency (POI) is a typical disorder of amenorrhea lasting for a minimum of 4 months. The typical characteristics comprised of declined estrogen and raised serum concentrations of follicle-stimulating hormone (FSH) in women <40-year-old, primarily originating from iatrogenic factors, karyotypic abnormalities, and genetic factors. However, the etiology of POI remains unknown in approximately 90% of cases. POI could lead to infertility, osteoporosis, cardiovascular disorder, and cognitive dysfunction. MicroRNAs (miRNAs) are a class of endogenous noncoding RNAs (ncRNAs) that can mediate post-translational silencing of the genes involved in the regulation of proliferation, differentiation, apoptosis, development, tumorigenesis, and hematopoiesis. Recently, the regulatory functions of miRNAs in the development of POI have been the topic of intensive research. The present review addresses the association of miRNAs' machinery genes (Dicer, Drosha, and XPO5) with POI and the miRNA expression profiles in the plasma of patients with POI. In addition, several specific miRNAs (miR-23a, miR-27a, miR-22-3p, miR-146a, miR-196a, miR-290-295, miR-423, and miR-608) related to POI are also examined in order to highlight the issues that deserve further investigation. A thorough understanding of the exact regulatory roles of miRNAs is imperative to gain novel insights into the etiology of idiopathic POI and offer new research directions in the field.

Disorganization of the germ cell pool leads to primary ovarian insufficiency

The mammalian ovary is an organ that controls female germ cell development, storing them and releasing mature oocytes for transporting to the oviduct. During the fetal stage, female germ cells change from a proliferative state to meiosis before forming follicles with the potential for the growth of surrounding somatic cells. Understanding of molecular and physiological bases of germ cell development in the fetal ovary contributed not only to the elucidation of genetic disorders in primary ovarian insufficiency (POI), but also to the advancement of novel treatments for patients with POI. Accumulating evidence indicates that mutations in NOBOX, DAZL and FIGLAgenes are associated with POI. In addition, cell biology studies revealed the important roles of these genes as essential translational factors for germ cell development. Recent insights into the role of the PI3K (phosphatidylinositol 3-kinase)-Akt signaling pathway in primordial follicle activation allowed the development of a new infertility treatment, IVA (in vitro activation), leading to successful pregnancy/delivery in POI patients. Furthermore, elucidation of genetic dynamics underlying female germ cell development could allow regeneration of oocytes from ES (embryonic stem)/iPS (induced pluripotent stem) cells in mammals. The purpose of this review is to summarize basic findings related to female germ cell development and potential clinical implications, especially focusing on POI etiologies. We also summarize evolving new POI therapies based on IVA as well as oocyte regeneration.

Genetics of primary ovarian insufficiency

Primary ovarian insufficiency (POI) is characterized by a loss of ovarian function before the age of 40 and account for one major cause of female infertility. POI relevance is continuously growing because of the increasing number of women desiring conception beyond 30 years of age, when POI prevalence is >1%. POI is highly heterogeneous and can present with ovarian dysgenesis and primary amenorrhea, or with secondary amenorrhea, and it can be associated with other congenital or acquired abnormalities. In most cases POI remains classified as idiopathic. However, the age of menopause is an inheritable trait and POI has a strong genetic component. This is confirmed by the existence of several candidate genes, experimental and natural models. The variable expressivity of POI defect may indicate that, this disease may frequently be considered as a multifactorial or oligogenic defect. The most common genetic contributors to POI are the X chromosome-linked defects. Here, we review the principal X-linked and autosomal genes involved in syndromic and non-syndromic forms of POI with the expectation that this list will soon be upgraded, thus allowing the possibility to predict the risk of an early age at menopause in families with POI.

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.

A homozygous NOBOX truncating variant causes defective transcriptional activation and leads to primary ovarian insufficiency

STUDY QUESTION

Does a novel homozygous NOBOX truncating variant, identified in whole exome sequencing (WES) of patients with primary ovarian insufficiency (POI), cause defective transcriptional activation of multiple oocyte-related genes?

SUMMARY ANSWER

A novel homozygous truncating mutation of NOBOX was confirmed to exhibit a loss-of-function effect using well-defined molecular and functional analyses.

WHAT IS KNOWN ALREADY

Several NOBOX mutations have been reported to be associated with POI but all of them are heterozygous mutations.

STUDY DESIGN, SIZE, DURATION

This is a cross sectional study in 96 patients diagnosed with POI and 211 women not diagnosed with POI in China.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Blood samples collected from the participants were subjected to whole exome sequencing. Full-length transcript of NOBOX was cloned directly from human fetal ovary (FO). Functional analysis was performed for a NOBOX sequence variant associated with POI.

MAIN RESULTS AND THE ROLE OF CHANCE

One novel homozygous truncating variant, chr7:144098161delC, in the NOBOX gene was found in a POI patient. The truncating variant showed a severe defect in transcriptional activation of GDF9 a well-known target NOBOX. Furthermore, using real-time quantitative PCR analysis, we found many oocyte-related genes were expressed at lower level in truncating variant cells than in control cells. In addition, we found that the truncated NOBOX lost its ability to induce the G2/M arrest.Notably, our results confirmed that the 1725 bp NOBOX transcript is expressed in human FO and is the only functional isoform in transcriptional activation assays.

LIMITATIONS REASONS FOR CAUTION

Although the in vitro assays demonstrated the loss-of-function effect of truncating mutation on NOBOX transcriptional activation, further studies are needed to validate its long-term effects on folliculogenesis and POI.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first homozygous mutation of NOBOX associated with POI showing a loss-of-function effect using well-defined molecular and functional analyses. These results will aid both researchers and clinicians in understanding the molecular pathology of NOBOX and POI to develop diagnostic assays or therapeutic approaches.

STUDY FUNDING/COMPETING INTERESTS

Research funding is provided by the Ministry of Science and Technology of China [2012CB944704; 2012CB966702], the National Natural Science Foundation of China [Grant number: 31171429] and Beijing Advanced Innovation Center for Structural Biology. The authors declare no conflict of interest.

Involvement of FOXL2 and RSPO1 in Ovarian Determination, Development, and Maintenance in Mammals

In mammals, sex determination is a process through which the gonad is committed to differentiate into a testis or an ovary. This process relies on a delicate balance between genetic pathways that promote one fate and inhibit the other. Once the gonad is committed to the female pathway, ovarian differentiation begins and, depending on the species, is completed during gestation or shortly after birth. During this step, granulosa cell precursors, steroidogenic cells, and primordial germ cells start to express female-specific markers in a sex-dimorphic manner. The germ cells then arrest at prophase I of meiosis and, together with somatic cells, assemble into functional structures. This organization gives the ovary its definitive morphology and functionality during folliculogenesis. Until now, 2 main genetic cascades have been shown to be involved in female sex differentiation. The first is driven by FOXL2, a transcription factor that also plays a crucial role in folliculogenesis and ovarian fate maintenance in adults. The other operates through the WNT/CTNNB1 canonical pathway and is regulated primarily by R-spondin1. Here, we discuss the roles of FOXL2 and RSPO1/WNT/ CTNNB1 during ovarian development and homeostasis in different models, such as humans, goats, and rodents.

The comparison of animal models for premature ovarian failure established by several different source of inducers

The objective of this study was to compare premature ovarian failure animal models established by several different source of inducers. Female ICR mice, KM mice, and SD rats were treated by cyclophosphamide at 120 mg/kg, busulfan at 12 mg/kg, cisplatin at 3 or 4 mg/kg, 4-vinylcyclohexene diepoxide at 160 mg/kg, 35% galactose food pellet, and tripterygium glycosides at 50 mg/kg, respectively. Parameters were analyzed by body weight, serum concentration level of related hormones, ovarian and uterine pathological examination. The results indicated the body weight of mice increased very slowly following single dose of cyclophosphamide (p < 0.05) with damaged ovary; repeated doses of cisplatin could induce body weight significantly decreased (p < 0.01) with a rising trend of serum LH concentration, declining tendency of serum E2 concentration and injured ovary and uterus; 4-vinylcyclohexene diepoxide also hindered the mice growing (p < 0.05) with damaged ovary and uterus; the body weight of mice feed by 35% galactose food pellet increased slowly (p < 0.05) with dramatically higher serum concentration level of galactose, albumin, and total protein (p < 0.001) and injured ovary. Busulfan and tripterygium glycosides did not present obvious evidences. In conclusion, the inducers presented their respective features in such animal models and should be appropriately applied in preventive methods.

Characterization and target genes of nine human PRD-like homeobox domain genes expressed exclusively in early embryos

PAIRED (PRD)-like homeobox genes belong to a class of predicted transcription factor genes. Several of these PRD-like homeobox genes have been predicted in silico from genomic sequence but until recently had no evidence of transcript expression. We found recently that nine PRD-like homeobox genes, ARGFX, CPHX1, CPHX2, DPRX, DUXA, DUXB, NOBOX, TPRX1 and TPRX2, were expressed in human preimplantation embryos. In the current study we characterized these PRD-like homeobox genes in depth and studied their functions as transcription factors. We cloned multiple transcript variants from human embryos and showed that the expression of these genes is specific to embryos and pluripotent stem cells. Overexpression of the genes in human embryonic stem cells confirmed their roles as transcription factors as either activators (CPHX1, CPHX2, ARGFX) or repressors (DPRX, DUXA, TPRX2) with distinct targets that could be explained by the amino acid sequence in homeodomain. Some PRD-like homeodomain transcription factors had high concordance of target genes and showed enrichment for both developmentally important gene sets and a 36 bp DNA recognition motif implicated in Embryo Genome Activation (EGA). Our data implicate a role for these previously uncharacterized PRD-like homeodomain proteins in the regulation of human embryo genome activation and preimplantation embryo development.

Insights into female germ cell biology: from in vivo development to in vitro derivations

Understanding the mechanisms of human germ cell biology is important for developing infertility treatments. However, little is known about the mechanisms that regulate human gametogenesis due to the difficulties in collecting samples, especially germ cells during fetal development. In contrast to the mitotic arrest of spermatogonia stem cells in the fetal testis, female germ cells proceed into meiosis and began folliculogenesis in fetal ovaries. Regulations of these developmental events, including the initiation of meiosis and the endowment of primordial follicles, remain an enigma. Studying the molecular mechanisms of female germ cell biology in the human ovary has been mostly limited to spatiotemporal characterizations of genes or proteins. Recent efforts in utilizing in vitro differentiation system of stem cells to derive germ cells have allowed researchers to begin studying molecular mechanisms during human germ cell development. Meanwhile, the possibility of isolating female germline stem cells in adult ovaries also excites researchers and generates many debates. This review will mainly focus on presenting and discussing recent in vivo and in vitro studies on female germ cell biology in human. The topics will highlight the progress made in understanding the three main stages of germ cell developments: namely, primordial germ cell formation, meiotic initiation, and folliculogenesis.

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.

The developmental origins of the mammalian ovarian reserve

The adult mammalian ovary is devoid of definitive germline stem cells. As such, female reproductive senescence largely results from the depletion of a finite ovarian follicle pool that is produced during embryonic development. Remarkably, the crucial nature and regulation of follicle assembly and survival during embryogenesis is just coming into focus. This developmental pathway involves the coordination of meiotic progression and the breakdown of germ cell cysts into individual oocytes housed within primordial follicles. Recent evidence also indicates that genetic and environmental factors can specifically perturb primordial follicle assembly. Here, we review the cellular and molecular mechanisms by which the mammalian ovarian reserve is established, highlighting the presence of a crucial checkpoint that allows survival of only the highest-quality oocytes.

Genetics of the ovarian reserve

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

The genetics of premature ovarian failure: current perspectives

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

Novel WT1 Missense Mutations in Han Chinese Women with Premature Ovarian Failure

Premature ovarian failure (POF) is a heterogeneous disease. Though dozens of candidate genes have been identified for the genetic etiology of POF, it is largely unexplained in majority of patients. Recently, Wt1^+/R394W mice was found to present POF-like phenotype, which indicates that WT1 might be a plausible candidate gene for non-syndromic POF. The coding region of WT1 gene was screened in 384 patients with POF and 6 novel variations were identified, including two missense mutations (p. Pro126Ser in exon1 and p. Arg370His in exon7) and four intronic variants (c.647-27C > T, c.647-13G > C, c.647-13G > A in intron1 and c.950 + 14T > C in intron 4). In vitro experiments showed that both mutant p. Pro126Ser and p. Arg370His repressed the expression of Amh and Cdh1, and induced the expression of Fshr and Cyp19 in mRNA level (P < 0.05). The expression changes of AMH, FSHR, CYP19 and CDH1 were confirmed by western blot. These genes (AMH, FSHR, CYP19 and CDH1) are required for granular cells (GCs) proliferation, differentiation and oocyte-GCs interaction. The novel mutant p. P126S and p. R370H in the WT1 gene potentially impaired GCs differentiation and oocyte-GCs interaction, which might result in loss of follicles prematurely. Therefore, WT1 is a plausible causal gene for POF.

Aetiological coding sequence variants in non-syndromic premature ovarian failure: From genetic linkage analysis to next generation sequencing

Premature ovarian failure (POF) is a frequent pathology affecting 1-1.5% of women under 40 years old. Despite advances in diagnosing and treating human infertility, POF is still classified as being idiopathic in 50-80% of cases, strongly suggesting a genetic origin for the disease. Different types of autosomal and X-linked genetic anomalies can originate the phenotype in syndromic and non-syndromic POF cases. Particular interest has been focused on research into non-syndromic POF causative coding variants during the past two decades. This has been based on the assumption that amino acid substitutions might modify the intrinsic physicochemical properties of functional proteins, thereby inducing pathological phenotypes. In this case, a restricted number of mutations might originate the disease. However, like other complex pathologies, POF might result from synergistic/compensatory effects caused by several low-to-mildly drastic mutations which have frequently been classified as non-functional SNPs. Indeed, reproductive phenotypes can be considered as quantitative traits resulting from the subtle interaction of many genes. Although numerous sequencing projects have involved candidate genes, only a few coding mutations explaining a low percentage of cases have been described. Such apparent failure to identify aetiological coding sequence variations might have been due to the inherent molecular complexity of mammalian reproduction and to the difficulty of simultaneously analysing large genomic regions by Sanger sequencing. The purpose of this review is to present the molecular and cellular effects caused by non-synonymous mutations which have been formally associated, by functional tests, with the aetiology of hypergonadotropic non-syndromic POF. Considerations have also been included regarding the polygenic nature of reproduction and POF, as well as future approaches for identifying novel aetiological genes based on next generation sequencing (NGS).

Concurrent DNA Copy-Number Alterations and Mutations in Genes Related to Maintenance of Genome Stability in Uninvolved Mammary Glandular Tissue from Breast Cancer Patients

Somatic mosaicism for DNA copy-number alterations (SMC-CNAs) is defined as gain or loss of chromosomal segments in somatic cells within a single organism. As cells harboring SMC-CNAs can undergo clonal expansion, it has been proposed that SMC-CNAs may contribute to the predisposition of these cells to genetic disease including cancer. Herein, the gross genomic alterations (>500 kbp) were characterized in uninvolved mammary glandular tissue from 59 breast cancer patients and matched samples of primary tumors and lymph node metastases. Array-based comparative genomic hybridization showed 10% (6/59) of patients harbored one to 359 large SMC-CNAs (mean: 1,328 kbp; median: 961 kbp) in a substantial portion of glandular tissue cells, distal from the primary tumor site. SMC-CNAs were partially recurrent in tumors, albeit with considerable contribution of stochastic SMC-CNAs indicating genomic destabilization. Targeted resequencing of 301 known predisposition and somatic driver loci revealed mutations and rare variants in genes related to maintenance of genomic integrity: BRCA1 (p.Gln1756Profs*74, p.Arg504Cys), BRCA2 (p.Asn3124Ile), NCOR1 (p.Pro1570Glnfs*45), PALB2 (p.Ser500Pro), and TP53 (p.Arg306*). Co-occurrence of gross SMC-CNAs along with point mutations or rare variants in genes responsible for safeguarding genomic integrity highlights the temporal and spatial neoplastic potential of uninvolved glandular tissue in breast cancer patients.

Genetics of primary ovarian insufficiency: new developments and opportunities

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

CSB-PGBD3 Mutations Cause Premature Ovarian Failure

Premature ovarian failure (POF) is a rare, heterogeneous disorder characterized by cessation of menstruation occurring before the age of 40 years. Genetic etiology is responsible for perhaps 25% of cases, but most cases are sporadic and unexplained. In this study, through whole exome sequencing in a non-consanguineous family having four affected members with POF and Sanger sequencing in 432 sporadic cases, we identified three novel mutations in the fusion gene CSB-PGBD3. Subsequently functional studies suggest that mutated CSB-PGBD3 fusion protein was impaired in response to DNA damage, as indicated by delayed or absent recruitment to damaged sites. Our data provide the first evidence that mutations in the CSB-PGBD3 fusion protein can cause human disease, even in the presence of functional CSB, thus potentially explaining conservation of the fusion protein for 43 My since marmoset. The localization of the CSB-PGBD3 fusion protein to UVA-induced nuclear DNA repair foci further suggests that the CSB-PGBD3 fusion protein, like many other proteins that can cause POF, modulates or participates in DNA repair.

Next generation sequencing in women affected by nonsyndromic premature ovarian failure displays new potential causative genes and mutations

OBJECTIVE

To identify new molecular actors involved in nonsyndromic premature ovarian failure (POF) etiology.

DESIGN

This is a retrospective case-control cohort study.

SETTING

University research group and IVF medical center.

PATIENT(S)

Twelve women affected by nonsyndromic POF. The control group included 176 women whose menopause had occurred after age 50 and had no antecedents regarding gynecological disease. A further 345 women from the same ethnic origin (general population group) were also recruited to assess allele frequency for potentially deleterious sequence variants.

INTERVENTION(S)

Next generation sequencing (NGS), Sanger sequencing, and bioinformatics analysis.

MAIN OUTCOME MEASURE(S)

The complete coding regions of 70 candidate genes were massively sequenced, via NGS, in POF patients. Bioinformatics and genetics were used to confirm NGS results and to identify potential sequence variants related to the disease pathogenesis.

RESULT(S)

We have identified mutations in two novel genes, ADAMTS19 and BMPR2, that are potentially related to POF origin. LHCGR mutations, which might have contributed to the phenotype, were also detected.

CONCLUSION(S)

We thus recommend NGS as a powerful tool for identifying new molecular actors in POF and for future diagnostic/prognostic purposes.

GDF9 is transiently expressed in oocytes before follicle formation in the human fetal ovary and is regulated by a novel NOBOX transcript

During human fetal ovary development, the process of primordial follicle formation is immediately preceded by a highly dynamic period of germ cell and somatic cell reorganisation. This is regulated by germ-cell specific transcription regulators, by the conserved RNA binding proteins DAZL and BOLL and by secreted growth factors of the TGFβ family, including activin βA: these all show changing patterns of expression preceding follicle formation. In mice, the transcription factor Nobox is essential for follicle formation and oocyte survival, and NOBOX regulates the expression of GDF9 in humans. We have therefore characterised the expression of GDF9 in relation to these known key factors during follicle formation in the human fetal ovary. mRNA levels of GDF9, BMP15 and NOBOX were quantified by qRT-PCR and showed dramatic increases across gestation. GDF9 protein expression was localised by immunohistochemistry to the same population of germ cells as those expressing activin βA prior to follicle formation but did not co-localise with either BOLL or DAZL. A novel NOBOX isoform was identified in fetal ovary that was shown to be capable of up-regulating the GDF9 promoter in reporter assays. Thus, during oogenesis in humans, oocytes go through a dynamic and very sharply demarcated sequence of changes in expression of these various proteins, even within individual germ cell nests, likely to be of major functional significance in determining selective germ cell survival at this key stage in ovarian development. Transcriptional variation may contribute to the range of age of onset of POI in women with NOBOX mutations.

New NOBOX mutations identified in a large cohort of women with primary ovarian insufficiency decrease KIT-L expression

CONTEXT

Primary ovarian insufficiency (POI) is a major cause of anovulation and infertility in women. This disease affects 1% of women before 40 years, and several genetic causes have been reported.

OBJECTIVE

The aim of the study was to evaluate the prevalence of NOBOX mutations in a new large cohort of women with POI and to characterize these variants and identify a NOBOX novel target gene.

PATIENTS AND METHODS

A total of 213 unrelated patients with POI were screened for NOBOX mutations, and luciferase reporter assays were performed for the mutations identified.

RESULTS

We reported 3 novel and 2 recurrent heterozygous missense NOBOX rare variants found in 12 patients but not in 724 alleles from ethnic-matched individual women with occurrence of menopause at a normal age. Their functional impact had been tested on the classic growth differentiation factor-9 (GDF9) promoter and on KIT-L, a new NOBOX target gene. The p.Gly91Thr, p.Gly111Arg, p.Arg117Trp, p.Lys371Thr, and p.Pro619Leu mutations were deleterious for protein function.

CONCLUSIONS

In our series, 5.6% of the patients with POI displayed heterozygous NOBOX mutations. We demonstrate that KIT-L could be now a direct NOBOX target. These findings replicate the high prevalence of the association between the NOBOX rare variants and POI.

Transcriptional profiling of five isolated size-matched stages of human preantral follicles

Little is known of the early stages of human follicular development and the complex processes that regulate follicular growth. To identify genes of potential importance, we analysed follicle-related transcripts in five populations of isolated size-matched human preantral follicles by microarray analysis. Oocyte-specific genes were found to be the most abundant and differentially expressed transcripts and included germ cell transcription factors LHX8 and SOHLH2 which were significantly down-regulated during preantral follicle development. Differentially expressed genes also included transcription factors of NOTCH signalling, IGF2, orphan nuclear receptor LRH-1, and homeobox gene HOXA7, indicating potentially important regulatory roles for these genes during early human folliculogenesis. We also found that FSHR mRNA and protein were present in the earliest stages of preantral follicles, whereas LHR was absent. In conclusion, our data identify specific oocyte and somatic genes in small human follicles that impact early follicle growth, and provide foundation for further analysis of the signalling pathways involved in early human folliculogenesis.

Intraovarian control of early folliculogenesis

Although hormonal regulation of ovarian follicle development has been extensively investigated, most studies concentrate on the development of early antral follicles to the preovulatory stage, leading to the successful use of exogenous FSH for infertility treatment. Accumulating data indicate that preantral follicles are under stringent regulation by FSH and local intraovarian factors, thus providing the possibility to develop new therapeutic approaches. Granulosa cell-derived C-type natriuretic factor not only suppresses the final maturation of oocytes to undergo germinal vesicle breakdown before ovulation but also promotes preantral and antral follicle growth. In addition, several oocyte- and granulosa cell-derived factors stimulate preantral follicle growth by acting through wingless, receptor tyrosine kinase, receptor serine kinase, and other signaling pathways. In contrast, the ovarian Hippo signaling pathway constrains follicle growth and disruption of Hippo signaling promotes the secretion of downstream CCN growth factors capable of promoting follicle growth. Although the exact hormonal factors involved in primordial follicle activation has yet to be elucidated, the protein kinase B (AKT) and mammalian target of rapamycin signaling pathways are important for the activation of dormant primordial follicles. Hippo signaling disruption after ovarian fragmentation, combined with treating ovarian fragments with phosphatase and tensin homolog (PTEN) inhibitors and phosphoinositide-3-kinase stimulators to augment AKT signaling, promote the growth of preantral follicles in patients with primary ovarian insufficiency, leading to a new infertility intervention for such patients. Elucidation of intraovarian mechanisms underlying early folliculogenesis may allow the development of novel therapeutic strategies for patients diagnosed with primary ovarian insufficiency, polycystic ovary syndrome, and poor ovarian response to FSH stimulation, as well as for infertile women of advanced reproductive age.

Risks associated with premature ovarian failure in Han Chinese women

In this retrospective study, the relationship between demographic characteristics, past medical history, general lifestyle habits and susceptibility of premature ovarian failure (POF) in Han Chinese population was investigated. Five hundred and fifty-three patients with POF and 400 women with normal ovarian function were recruited. A questionnaire was designed to gather information from responders. Logistic regression was carried out to calculate odds ratios (OR), 95% confidence intervals (95% CI) and P-values. History of pelvic surgery, mumps, having relatives with menstrual abnormalities and exposure to chemical agents were significantly associated with increased risk of POF (OR 5.53 [2.15 to 14.23]; 3.26 [2.38 to 4.47]; 28.12 [8.84 to 89.46]; 4.47 [2.09 to 9.58]). Vegetarian diet, tea and mineral water consumption reduced the risk of POF (OR 0.27 [0.19 to 0.37]; 0.04 [0.03 to 0.07]; 0.63 [0.47 to 0.85], respectively). Heredity, pelvic surgery, mumps and exposure to chemical agents were identified as risk factors for POF, whereas vegetarian diet, tea consumption and mineral water drinking were protective. Therefore, genetic consultation could help those women whose relatives manifested an early or premature menopause to avoid the consequences of possible premature ovarian function cessation. Avoidance of exposure to endocrine disrupters and flavonoids intake should be considered.

Transcription factor SOHLH1 potentially associated with primary ovarian insufficiency

OBJECTIVE

To investigate whether gene variants of SOHLH1 exist in Chinese and Serbian patients with primary ovarian insufficiency (POI).

DESIGN

Case-control genetic study.

SETTING

University hospitals.

PATIENT(S)

A total of 364 Han Chinese and 197 Serbian women with nonsyndromic POI and ethnically matched controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

SOHLH1 gene sequencing.

RESULT(S)

We found 10 novel heterozygous variants in our cohorts of 561 women with POI but none in the 600 ethnically matched controls. Statistical and bioinformatic analyses indicated that three of the eight variants in Chinese POI cases are potentially disease causing. They comprise two missense variants (p.Ser317Phe and p.Glu376Lys) that might each change activity of the SOHLH1 protein as a transcription factor and one variant (c.*118C>T) located in the 3' untranslated region of the SOHLH1 gene, which might generate a new binding site for the microRNA hsa-miR-888-5p. Of the two variants in the Serbian POI cases, both were synonymous, and no missense variant was identified. The allele frequencies of some known single-nucleotide polymorphisms were statistically significantly different between patients and controls in both the Chinese and Serbian groups.

CONCLUSION(S)

Our results suggest that SOHLH1 may be regarded as a new candidate gene for POI.

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

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