Genome-wide linkage in a highly consanguineous pedigree reveals two novel loci on chromosome 7 for non-syndromic familial Premature Ovarian Failure

Oligogenic basis of premature ovarian insufficiency: an observational study

BACKGROUND

The etiology of premature ovarian insufficiency, that is, the loss of ovarian activity before 40 years of age, is complex. Studies suggest that genetic factors are involved in 20-25% of cases. The aim of this study was to explore the oligogenic basis of premature ovarian insufficiency.

RESULTS

Whole-exome sequencing of 93 patients with POI and whole-genome sequencing of 465 controls were performed. In the gene-burden analysis, multiple genetic variants, including those associated with DNA damage repair and meiosis, were more common in participants with premature ovarian insufficiency than in controls. The ORVAL-platform analysis confirmed the pathogenicity of the RAD52 and MSH6 combination.

CONCLUSIONS

The results of this study indicate that oligogenic inheritance is an important cause of premature ovarian insufficiency and provide insights into the biological mechanisms underlying premature ovarian insufficiency.

Shared Genetics Between Age at Menopause, Early Menopause, POI and Other Traits

Reproductive ageing leading to menopause is characterized by depletion of follicles and its regulating mechanisms are only partly understood. Early age at menopause and premature ovarian insufficiency (POI) are associated with several other traits such as cardiovascular disease, dyslipidemia, osteoporosis and diabetes. In large cohorts of Northern European women hundreds of Single Nucleotide Polymorphisms (SNPs) have been identified to be associated with age at menopause. These SNPs are located in genes enriched for immune and mitochondrial function as well as DNA repair and maintenance processes. Genetic predisposition to earlier menopause might also increase the risk of other associated traits. Increased risk for cardiovascular disease in women has been associated with age at menopause lowering SNPs. Pleiotropy between early age at menopause and increased mortality from coronary artery disease has been observed, implicating that genetic variants affecting age at menopause also affect the risk for coronary deaths. This review will discuss the shared genetics of age at menopause with other traits. Mendelian Randomization studies implicate causal genetic association between age at menopause and age at menarche, breast cancer, ovarian cancer, BMD and type 2 diabetes. Although the shared biological pathways remain to be determined, mechanisms that regulate duration of estrogen exposure remain an important focus.

Fertility preservation in women for medical and social reasons: Oocytes vs ovarian tissue

Approximately 10% of cancers occur in women under 45 years of age. Chemotherapy, radiotherapy, and bone marrow transplantation cure more than 90% of cancer in women, but can result in premature ovarian insufficiency depending on follicular reserve, age, and drugs used. Some benign diseases are also indications for fertility preservation, particularly those requiring chemotherapy (like thalassemia and lupus), recurrent endometriosis, and family history of premature menopause. Social reasons also account for a large proportion of women who wish to postpone pregnancy. This article discusses the two main strategies for fertility preservation, namely oocyte vitrification and ovarian tissue cryopreservation, examining the indications and results of these options. Oocyte cryopreservation is an effective approach, but further studies are needed in cancer patients to ensure the excellent outcomes obtained in women without cancer or in egg donation programs. For prepubertal girls or cases where immediate therapy is required, cryopreservation of ovarian tissue is the only available option.

Primary ovarian insufficiency, meiosis and DNA repair

Premature ovarian insufficiency (POI) is a major cause of female infertility. It is a heterogeneous disease that affects about 1% of women under 40 years of age. POI may be due to abnormal follicle stock formation, increased follicular atresia, impaired recruitment of dominant follicles, blocked follicular maturation or rapid depletion of the follicular stock. It remains idiopathic in most cases but the existence of familial cases shows that it can have a genetic origin. Next generation sequencing (NGS) strategies have allowed the identification of new genes involved in the etiology of POI. Here, I briefly describe some studies demonstrating that pathogenic variants in ‘DNA repair and meiotic genes’ underlie POI. Some of the examples show the power of the combination of classical genetics and NGS in the discovery of novel ‘POI genes’.

Ovarian tissue cryopreservation: Low usage rates and high live-birth rate after transplantation

Introduction

The likelihood of survival after cancer treatment among young women with cancer has increased considerably, quality of life after treatment has drawn more attention. However, in young fertile women, fertility preservation is an important issue with regard to quality of life. One of the options of fertility preservation is ovarian tissue cryopreservation. The purpose of this follow‐up study is to present our clinical experiences and evaluate the long‐term follow up of ovarian cryopreservation to improve future patient selection.

Material and methods

From July 2002 to December 2015 at the Leiden University Hospital, the Netherlands, 69 young women underwent ovarian tissue cryopreservation when they were at risk of iatrogenic premature ovarian insufficiency. Follow‐up data with regard to ovarian function were obtained until October 2018, from medical records and questionnaires.

Results

Of the 69 women in whom ovarian tissue cryopreservation was performed, 12 died (15.9%), 57 were approached to participate, of which 6 were lost to follow up. The indications for ovarian tissue cryopreservation were malignant (81.1%) and benign (18.9%) diseases in which gonadotoxic treatment was scheduled. In total, twenty women (39.2%) are known to have premature ovarian insufficiency due to gonadotoxic treatment. Fifteen women conceived spontaneously, and delivered 25 babies. In this cohort, the usage rate of autotransplantation is 8.7% (7/69). In total, nine autotransplantations of cryopreserved ovarian tissue were performed in seven patients (of which 1 ovarian tissue cryopreservation was performed in another hospital) after which 6 babies were born to four women, giving a live‐birth rate of 57%.

Conclusions

Ovarian tissue cryopreservation followed by autotransplantation is an effective method to restore fertility (live‐birth rate of 57%). The usage rate of 8.7% (6/69) indicates that more knowledge about the risk of premature ovarian insufficiency after gonadotoxic treatment is needed to be able to offer ovarian tissue cryopreservation more selectively.

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.

A review of the reproductive consequences of consanguinity

BACKGROUND

Consanguinity is the close union, sexual relationship or marriage between persons who have common biological ancestors usually up to about 2nd cousins. Contrary to general opinion consanguinity is quite common and is practiced worldwide. It is an important topic as while rates of consanguineous unions in certain society have decreased over time, rates have remained stable or increased in other societies with rates as high as 80.6% in some communities. Our aim was to conduct a review looking at general aspects of consanguinity and any published reproductive outcomes in literature. We also looked at possible future directions that could be relevant in the management of the consanguineous couple to help improve reproductive outcomes.

METHOD

We conducted a PUBMED, CINAHL, Web of Knowledge and Google Scholar search looking at articles on consanguinity. Consanguinity articles related to pregnancy and reproduction were searched using additional filters looking at our specific areas of interest. All relevant publications up to March 2015 were reviewed. Additional search for relevant articles pertaining to pre implantation genetic diagnosis for future directions in the management of the consanguineous couple was done. Most publications were found in books, on line articles and journals. Most were retrospective, population or cohort studies.

RESULT

Consanguinity is practiced by up to 10% of the world's population with rates ranging from 80.6% in certain provinces in the Middle East to less than 1% in western societies. It predates Islam and has been practiced since Old Testament times. The most commonly cited reason for consanguinity is sociocultural and socioeconomic although it is also more common in certain religions. In areas where rates of Consanguinity are reducing urban migration and increasing education rates are thought to be contributory. Congenital malformations have long been established to be higher in consanguineous couples above the background rate (4.5% Vs 1%).Due to "Founder effect" or a common ancestor, Consanguinity is most commonly associated with Inborn errors of metabolism most of which are autosomal recessive. Consanguinity increases the incidence of multifactorial disorders such as diabetes, cardiovascular disorders, obesity and certain types of cancers. These may in turn affect reproductive outcomes. It may also affect fertility rates. Pregnancy outcomes like increased pregnancy wastages and preterm labor have been reported with consanguinity. Other studies produced conflicting evidence on its effect regarding outcomes like hypertensive disorders of pregnancy and Intrauterine growth restriction.

CONCLUSION

Consanguinity continues to be practiced worldwide and in some countries rates are increasing. The main reason for the practice appears to be sociocultural and socioeconomic although religious beliefs is a contributory factor. The most significant effects on reproductive outcomes are mostly due to autosomal recessive inherited conditions and inborn errors of metabolism. It also significantly increases the inheritance of certain multifactorial disorders like diabetes which may indirectly affect reproductive outcomes. In the future with the completion of the study of the whole human Genome and current advances in Pre implantation Genetic diagnosis and screening it may be possible to mitigate some of the adverse reproductive outcomes associated with consanguinity.

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.

Premature Ovarian Insufficiency: An Adolescent Series

STUDY OBJECTIVE

To study the presentation and causes of premature ovarian insufficiency (POI) in adolescents.

DESIGN

Retrospective notes review.

SETTING

Tertiary referral outpatient clinic for pediatric and adolescent gynecology.

PARTICIPANTS

Adolescents with POI.

INTERVENTIONS

Standard POI evaluation.

MAIN OUTCOME MEASURES

Age and clinical symptoms at presentation, causative factors for POI, if identified.

RESULTS

We identified 22 girls with POI, with a mean age of 15.6 years. Eight of them presented with delayed puberty, 3 with primary amenorrhea, and the remainder presented with either irregular bleeding (n = 9) or secondary amenorrhea (n = 2). For those who presented with delayed puberty, only 3 were found to have a sex chromosome abnormality. A clear cause for the POI was identified in 3 further cases.

CONCLUSION

Although POI in adolescents traditionally is associated with primary amenorrhea and delayed puberty, a proportion of girls will present with irregular bleeding that might be mistaken for expected menstrual disturbances of puberty, thus delaying the diagnosis. We identified a clear cause for POI in 6 cases. Although there were no familial cases of POI, it remains a possibility that genetic reasons might be involved in the pathogenesis.

Mutation analysis of NANOS3 in Brazilian women with primary ovarian failure

OBJECTIVES:

Primary ovarian failure is a rare disorder, and approximately 90% of cases are of unknown etiology. The aim of this study was to search for mutations in NANOS3, a gene that was recently related to the etiology of primary ovarian failure, in a group of Brazilian women.

METHODS:

We screened for NANOS3 DNA variants in 30 consecutive women who were previously diagnosed with primary ovarian failure, of unknown etiology and compared the results with those from 185 women with normal fertility. The NANOS3 gene was amplified by polymerase chain reaction using pairs of specific primers and then sequenced. The resulting sequences were compared with control sequences available in the National Center for Biotechnology and Information database.

RESULTS:

No mutations in NANOS3 were found in primary ovarian failure patients, but four previously described polymorphisms were identified at a similar frequency in the control and primary ovarian failure groups.

CONCLUSIONS:

Mutations in NANOS3 were not associated with primary ovarian failure in the present cohort.

Ovarian Physiology and GWAS: Biobanks, Biology, and Beyond

Ovarian function is central to female fertility, and several genome-wide association studies (GWAS) have been carried out to elucidate the genetic background of traits and disorders that reflect and affect ovarian physiology. While GWAS have been successful in reporting numerous genetic associations and highlighting involved pathways relevant to reproductive aging, for ovarian disorders, such as premature ovarian insufficiency and polycystic ovary syndrome, research has lagged behind due to insufficient study sample size. Novel approaches to study design and analysis methods that help to fit GWAS findings into biological context will improve our knowledge about genetics governing ovarian function in fertility and disease, and provide input for clinical tools and better patient management.

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).

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.

Genetics of primary ovarian insufficiency: a review

Primary ovarian insufficiency is one of the main causes of female infertility owing to an abnormal ovarian reserve. Its relevance has increased in more recent years due to the fact that age of motherhood is being delayed in developed countries, with the risk of having either primary ovarian insufficiency or less chances of pregnancy when women consider the option of having their first baby. Several exogenous factors can lead to this event, such us viral infections, metabolomic dysfunction, autoimmune diseases, and environmental or iatrogenic factors, although in most cases the mechanism that leads to the disorder is unknown. Genetic factors represent the most commonly identified cause and the impact of sex chromosome abnormalities (e.g., Turner syndrome or X structural abnormalities), autosomal and X-linked mutations on the genesis of primary ovarian insufficiency has also been well described. Yet in most cases, the genetic origin remains unknown and there are multiple candidate genes. This review aims to collect all the genetic abnormalities and genes associated with syndromic and non syndromic primary ovarian insufficiency that have been published in the literature to date using the candidate-gene approach and a genome-wide analysis.

STAG3 is a strong candidate gene for male infertility

Oligo- and azoospermia are severe forms of male infertility. However, known genetic factors account only for a small fraction of the cases. Recently, whole-exome sequencing in a large consanguineous family with inherited premature ovarian failure (POF) identified a homozygous frameshift mutation in the STAG3 gene leading to a premature stop codon. STAG3 encodes a meiosis-specific subunit of the cohesin complex, a large proteinaceous ring with DNA-entrapping ability that ensures sister chromatid cohesion and enables correct synapsis and segregation of homologous chromosomes during meiosis. The pathogenicity of the STAG3 mutations was functionally validated with a loss-of-function mouse model for STAG3 in oogenesis. However, and since none of the male members of this family was homozygous for the mutant allele, we only could hypothesized its putative involvement in male infertility. In this report, we show that male mice devoid of Stag3 display a severe meiotic phenotype that includes a meiotic arrest at zygonema-like shortening of their chromosome axial elements/lateral elements, partial loss of centromeric cohesion at early prophase and maintenance of the ability to initiate but not complete RAD51- and DMC1-mediated double-strand break repair, demonstrating that STAG3 is a crucial cohesin subunit in mammalian gametogenesis and supporting our proposal that STAG3 is a strong candidate gene for human male infertility.

Mutant cohesin in premature ovarian failure

Premature ovarian failure is a major cause of female infertility. The genetic causes of this disorder remain unknown in most patients. Using whole-exome sequence analysis of a large consanguineous family with inherited premature ovarian failure, we identified a homozygous 1-bp deletion inducing a frameshift mutation in STAG3 on chromosome 7. STAG3 encodes a meiosis-specific subunit of the cohesin ring, which ensures correct sister chromatid cohesion. Female mice devoid of Stag3 are sterile, and their fetal oocytes are arrested at early prophase I, leading to oocyte depletion at 1 week of age.

Genetic analysis of BMP4 gene in Chinese Han female population with premature ovarian insufficiency

The bone morphogenetic protein 4 (BMP4) gene is related to development of female reproductive organs in animal models. However, to date, there has been no consensus on the relationship between mutations in BMP4 and premature ovarian insufficiency (POI) in human beings. To analyze variations in BMP4 in Chinese women with POI, we sequenced two coding regions of BMP4 in 99 Han Chinese women with POI after DNA extraction and amplification by polymerase chain reaction (PCR). We found no any mutation in the BMP4 coding regions. Only one SNP rs17563 was detected among women with POI. However, the allele frequency of rs17563 presented no significant differences between POI patients and the international HapMap Project data for CHB and CHD. Our findings suggest that the BMP4 gene may not represent a risk factor in the development of POI among Chinese Han women.

[Premature ovarian failures]

Premature ovarian failure (POF) is clinically suspected by amenorrhea and confirmed by an elevated FSH serum level above 40 mUI/L (even 20 mUI/L) twice, in a woman before the age of 40. Prevalence of POF is between 1 to 2% in women. In 90% of cases, no aetiology is identified. Obvious causes are chemotherapy, pelvic radiotherapy, ovarian surgery and diethylstilbestrol exposure in utero. A karyotype should be performed as Turner Syndrome is the most frequent genetic cause of POF. Some X abnormalities such as X deletion or X autosome translocation can be found. FMR1 pre-mutation (fragile X syndrome) should be searched for, even though no cases of mental retardation are known, in the family. Other genetic abnormalities can be suggested by associated symptoms (i.e.: FOXL2, SF1 mutations). Auto-immune aetiology can be suspected if other auto-immune features are present, however, there are no reliable auto-antibodies to confirm auto-immunity in POF. Treatment of POF is based on hormonal replacement therapy in order to avoid estrogen deficiency, suppress vasomotor symptoms and avoid bone loss as well as cardiovascular risk. Estrogens should be associated with progesterone or a progestin, at least up to the age of 51. Patients with POF should be informed that spontaneous pregnancies may occur (in 5% of cases). In case of desire of pregnancy, the patient should be oriented to a specialized unit for in vitro fertilization with oocyte donation. Psychological support is essential and should be part of the treatment. POF is associated with an increased risk of emotional distress and depression. No preventive treatment of POF is available so far.