Identification of variants in pleiotropic genes causing "isolated" premature ovarian insufficiency: implications for medical practice

Adult-onset vanishing white matter disease due to a novel compound heterozygous EIF2B2 mutation: a case report and brief review

BACKGROUND AND OBJECTIVES

Vanishing white matter disease (VWMD) is an autosomal recessive leukoencephalopathy caused by mutations in the EIF2B1-5 genes, typically rare in adulthood. We present a case of adult-onset VWMD with a novel EIF2B2 mutation.

METHODS

We collected the patient's clinical data, cerebrospinal fluid (CSF) results, laboratory tests, imaging features, genetic analysis, and follow-up data over a 4-year period.

RESULTS

A 40-year-old male patient presented with difficulty walking and leg pain. Neurological examination revealed acalculia, slow reaction times, and ataxia. Magnetic resonance imaging (MRI) scans showed diffuse, symmetric lesions with cerebrospinal fluid-like signals predominantly in the subcortical, periventricular, and cerebellar white matter. Genetic testing identified a compound heterozygous mutation in EIF2B2, consisting of a novel nonsense mutation (c.378 T > G, p.Tyr126*) and a reported missense mutation (c.818A > G, p.Lys273Arg) (NM_014239.4).

DISCUSSIONS

This report highlights the diverse phenotypic manifestations of VWMD and underscores the importance of considering EIF2B2 mutations in adult male patients with bilaterally symmetric hyperintensities in white matter and slowly progressive symptoms.

The impact of immunity on the risk of coronary artery disease: insights from a multiomics study

BACKGROUND

Immune inflammation is intricately associated with coronary artery disease (CAD) progression, necessitating the pursuit of more efficacious therapeutic strategies. This study aimed to uncover potential therapeutic targets for CAD and myocardial infarction (MI) by elucidating the causal connection between regulatory immune-related genes (RIRGs) and these disorders.

METHODOLOGY

We performed summary data-based Mendelian randomization analysis to assess the therapeutic targets linked to expression quantitative trait loci and methylation quantitative trait loci of RIRGs in relation to CAD and MI. Independent validation cohorts and datasets from coronary artery and left ventricular heart tissue were analyzed. To strengthen causal inference, colocalization analysis and PhenoScanner phenotype scans were employed.

RESULTS

Utilizing multiomics integration, we pinpointed EIF2B2, FCHO1, and DDT as CAD risk genes. Notably, EIF2B2 and FCHO1 displayed significant associations with MI. High EIF2B2 expression, regulated by cg16144293, heightened CAD and MI risk at rs175438. In contrast, enhanced FCHO1 expression, modulated by cg18329931, reduced CAD and MI risk at rs13382133. DDT upregulation influenced by cg11060661 and cg09664220 was associated with decreased CAD risk at rs5760120. Colocalization analysis firmly established these relationships.

CONCLUSION

EIF2B2, FCHO1, and DDT represent risk loci for CAD progression within RIRGs. Our identification of these genes enhances understanding of CAD pathogenesis and directs future drug development efforts.

Defects in meiosis I contribute to the genesis of androgenetic hydatidiform moles

To identify novel genes responsible for recurrent hydatidiform moles (HMs), we performed exome sequencing on 75 unrelated patients who were negative for mutations in the known genes. We identified biallelic deleterious variants in 6 genes, FOXL2, MAJIN, KASH5, SYCP2, MEIOB, and HFM1, in patients with androgenetic HMs, including a familial case of 3 affected members. Five of these genes are essential for meiosis I, and their deficiencies lead to premature ovarian insufficiency. Advanced maternal age is the strongest risk factor for sporadic androgenetic HM, which affects 1 in every 600 pregnancies. We studied Hfm1-/- female mice and found that these mice lost all their oocytes before puberty but retained some at younger ages. Oocytes from Hfm1-/- mice initiated meiotic maturation and extruded the first polar bodies in culture; however, their meiotic spindles were often positioned parallel, instead of perpendicular, to the ooplasmic membrane at telophase I, and some oocytes extruded the entire spindle with all the chromosomes into the polar bodies at metaphase II, a mechanism we previously reported in Mei1-/- oocytes. The occurrence of a common mechanism in two mouse models argues in favor of its plausibility at the origin of androgenetic HM formation in humans.

Primary ovarian insufficiency: update on clinical and genetic findings

Primary ovarian insufficiency (POI) is a disorder of insufficient ovarian follicle function before the age of 40 years with an estimated prevalence of 3.7% worldwide. Its relevance is emerging due to the increasing number of women desiring conception late or beyond the third decade of their lives. POI clinical presentation is extremely heterogeneous with a possible exordium as primary amenorrhea due to ovarian dysgenesis or with a secondary amenorrhea due to different congenital or acquired abnormalities. POI significantly impacts non only on the fertility prospect of the affected women but also on their general, psychological, sexual quality of life, and, furthermore, on their long-term bone, cardiovascular, and cognitive health. In several cases the underlying cause of POI remains unknown and, thus, these forms are still classified as idiopathic. However, we now know the age of menopause is an inheritable trait and POI has a strong genetic background. This is confirmed by the existence of several candidate genes, experimental and natural models. The most common genetic contributors to POI are the X chromosome-linked defects. Moreover, the variable expressivity of POI defect suggests it can be considered as a multifactorial or oligogenic defect. Here, we present an updated review on clinical findings and on the principal X-linked and autosomal genes involved in syndromic and non-syndromic forms of POI. We also provide current information on the management of the premature hypoestrogenic state as well as on fertility preservation in subjects at risk of POI.

Biallelic FANCA variants detected in sisters with isolated premature ovarian insufficiency

Premature ovarian insufficiency is a common form of female infertility affecting up to 4% of women and characterised by amenorrhea with elevated gonadotropin before the age of 40. Oocytes require controlled DNA breakage and repair for homologous recombination and the maintenance of oocyte integrity. Biallelic disruption of the DNA damage repair gene, Fanconi anemia complementation group A (FANCA), is a common cause of Fanconi anaemia, a syndrome characterised by bone marrow failure, cancer predisposition, physical anomalies and POI. There is ongoing dispute about the role of heterozygous FANCA variants in POI pathogenesis, with insufficient evidence supporting causation. Here, we have identified biallelic FANCA variants in French sisters presenting with POI, including a novel missense variant of uncertain significance and a likely pathogenic deletion that initially evaded detection. Functional studies indicated no discernible effect on DNA damage sensitivity in patient lymphoblasts. These novel FANCA variants add evidence that heterozygous loss of one allele is insufficient to cause DNA damage sensitivity and POI. We propose that intragenic deletions, that are relatively common in FANCA, may be missed without careful analysis, and could explain the presumed causation of heterozygous variants. Accurate variant curation is critical to optimise patient care and outcomes.

Ovarioleukodystrophy Due to EIF2B Genes: Systematic Review and Case Report

Leukodystrophies comprise a spectrum of genetic disorders affecting white matter (WM) formation in the central nervous system (CNS), of which vanishing white matter disease (VWMD) is one. VWMD presents with progressive neurological deterioration and a variety of manifestations. Ovarioleukodystrophy, a subtype of VWMD, exhibits a distinctive clinical profile encompassing both CNS WM alterations and ovarian dysfunction. Variants in genes of the eukaryotic translation initiation factor 2B (EIF2B) complex affect the full form and are implicated in VWMD, including ovarioleukodystrophy. This work aimed to systematically review all published cases of ovarioleukodystrophy associated with variants in the EIF2B1-5 gene complex based on the first case identified in a Mexican population. We performed a systematic review according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines of published cases of ovarioleukodystrophy associated with the EIF2B gene complex, including a newly identified case from Mexico. We identified 207 publications using PUBMED, SCOPUS, and PMC databases. One hundred fifty-one publications were eliminated due to duplicates, titles, abstracts, or other reasons, while 56 publications were revised, of which 29 were eliminated because they dealt with other genes or non-human research, and 27 reports were assessed for eligibility. Finally, 14 reports describing ovarian involvement, neuroimaging, and molecular variants were included. Our review identified 20 cases worldwide, with a median age of onset of 19 years. Clinical features included WM involvement, ovarian abnormalities, gait disturbances, epilepsy, cognitive and language impairment, and other neurological manifestations. Neuroimaging showed characteristic WM changes, highlighting the importance of MRI in diagnosis. Missense variants predominated among the identified genetic mutations, especially in the EIF2B4 and EIF2B5 genes. Ovarioleukodystrophy is an ultra-rare disorder with a wide range of clinical manifestations and ovarian changes. Gynecological evaluation is crucial in suspected cases of ovarioleukodystrophy, as ovarian manifestations may precede neurological symptoms. The role of MRI is crucial in the diagnostic approach to this entity. Continued collaborative efforts are essential to elucidate genotype-phenotype correlations, improve clinical management, and promote therapeutic advances for this rare disorder.

Pharmacogenomic studies of fertility outcomes in pediatric cancer survivors - A systematic review

For the same age, sex, and dosage, there can be significant variation in fertility outcomes in childhood cancer survivors. Genetics may explain this variation. This study aims to: (i) review the genetic contributions to infertility, (ii) search for pharmacogenomic studies looking at interactions of cancer treatment, genetic predisposition and fertility-related outcomes. Systematic searches in MEDLINE Ovid, Embase Classic+Embase, and PubMed were conducted using the following selection criteria: (i) pediatric, adolescent, and young adult cancer survivors, below 25 years old at the time of diagnosis, (ii) fertility outcome measures after cancer therapy, (iii) genetic considerations. Studies were excluded if they were (i) conducted in animal models, (ii) were not published in English, (iii) editorial letters, (iv) theses. Articles were screened in Covidence by at least two independent reviewers, followed by data extraction and a risk of bias assessment using the Quality in Prognostic Studies tool. Eight articles were reviewed with a total of 29 genes. Outcome measures included sperm concentration, azoospermia, AMH levels, assessment of premature menopause, ever being pregnant or siring a pregnancy. Three studies included replication cohorts, which attempted replication of SNP findings for NPY2R, BRSK1, FANCI, CYP2C19, CYP3A4, and CYP2B6. Six studies were rated with a high risk of bias. Differing methods may explain a lack of replication, and small cohorts may have contributed to few significant findings. Larger, prospective longitudinal studies with an unbiased genome-wide focus will be important to replicate significant results, which can be applied clinically.

A Human Homozygous HELQ Missense Variant Does Not Cause Premature Ovarian Insufficiency in a Mouse Model

Disruption of meiosis and DNA repair genes is associated with female fertility disorders like premature ovarian insufficiency (POI). In this study, we identified a homozygous missense variant in the HELQ gene (c.596 A>C; p.Gln199Pro) through whole exome sequencing in a POI patient, a condition associated with disrupted ovarian function and female infertility. HELQ, an enzyme involved in DNA repair, plays a crucial role in repairing DNA cross-links and has been linked to germ cell maintenance, fertility, and tumour suppression in mice. To explore the potential association of the HELQ variant with POI, we used CRISPR/Cas9 to create a knock-in mouse model harbouring the equivalent of the human HELQ variant identified in the POI patient. Surprisingly, Helq knock-in mice showed no discernible phenotype, with fertility levels, histological features, and follicle development similar to wild-type mice. Despite the lack of observable effects in mice, the potential role of HELQ in human fertility, especially in the context of POI, should not be dismissed. Larger studies encompassing diverse ethnic populations and alternative functional approaches will be necessary to further examine the role of HELQ in POI. Our results underscore the potential uncertainties associated with genomic variants and the limitations of in vivo animal modelling.

DNA double-strand break genetic variants in patients with premature ovarian insufficiency

Premature ovarian insufficiency (POI) is a clinically heterogeneous disease that may seriously affect the physical and mental health of women of reproductive age. POI primarily manifests as ovarian function decline and endocrine disorders in women prior to age 40 and is an established cause of female infertility. It is crucial to elucidate the causative factors of POI, not only to expand the understanding of ovarian physiology, but also to provide genetic counselling and fertility guidance to affected patients. Factors leading to POI are multifaceted with genetic factors accounting for 7% to 30%. In recent years, an increasing number of DNA damage-repair-related genes have been linked with the occurrence of POI. Among them, DNA double-strand breaks (DSBs), one of the most damaging to DNA, and its main repair methods including homologous recombination (HR) and non-homologous end joining (NHEJ) are of particular interest. Numerous genes are known to be involved in the regulation of programmed DSB formation and damage repair. The abnormal expression of several genes have been shown to trigger defects in the overall repair pathway and induce POI and other diseases. This review summarises the DSB-related genes that may contribute to the development of POI and their potential regulatory mechanisms, which will help to further establish role of DSB in the pathogenesis of POI and provide theoretical guidance for the study of the pathogenesis and clinical treatment of this disease.

LARS2 variants can present as premature ovarian insufficiency in the absence of overt hearing loss

Premature ovarian insufficiency (POI) affects 1 in 100 women and is a leading cause of female infertility. There are over 80 genes in which variants can cause POI, with these explaining only a minority of cases. Whole exome sequencing (WES) can be a useful tool for POI patient management, allowing clinical care to be personalized to underlying cause. We performed WES to investigate two French sisters, whose only clinical complaint was POI. Surprisingly, they shared one known and one novel likely pathogenic variant in the Perrault syndrome gene, LARS2. Using amino-acylation studies, we established that the novel missense variant significantly impairs LARS2 function. Perrault syndrome is characterized by sensorineural hearing loss in addition to POI. This molecular diagnosis alerted the sisters to the significance of their difficulty in following conversation. Subsequent audiology assessment revealed a mild bilateral hearing loss. We describe the first cases presenting with perceived isolated POI and causative variants in a Perrault syndrome gene. Our study expands the phenotypic spectrum associated with LARS2 variants and highlights the clinical benefit of having a genetic diagnosis, with prediction of potential co-morbidity and prompt and appropriate medical care, in this case by an audiologist for early detection of hearing loss.

Next-generation sequencing of 500 POI patients identified novel responsible monogenic and oligogenic variants

BACKGROUND

Premature ovarian insufficiency refers to the loss of ovarian function before 40 years of age. The etiology is heterogeneous, and genetic factors account for 20-25% of cases. However, how to transform genetic findings to clinical molecular diagnose remains a challenge. To identify potential causative variations for POI, a next generation sequencing panel with 28 known causative genes of POI was designed, and a large cohort of 500 Chinese Han patients was screened directly. Pathogenic evaluation of the identified variants and the phenotype analysis were performed according to monogenic or oligogenic variants.

RESULTS

A total of 14.4% (72/500) of the patients carried 61 pathogenic or likely pathogenic variants in 19 of the genes in the panel. Interestingly, 58 variants (95.1%, 58/61) were firstly identified in patients with POI. FOXL2 harbored the highest occurrence frequency (3.2%, 16/500), among whom presented with isolated ovarian insufficiency instead of blepharophimosis-ptosis-epicanthus inversus syndrome. Moreover, luciferase reporter assay confirmed variant p.R349G, which account for 2.6% of POI cases, impaired the transcriptional repressive effect of FOXL2 on CYP17A1. The novel compound heterozygous variants in NOBOX and MSH4 were confirmed by pedigree haplotype analysis, and digenic heterozygous variants in MSH4 and MSH5 were firstly identified. Furthermore, nine patients (1.8%, 9/500) with digenic or multigenic pathogenic variants presented with delayed menarche, early onset of POI and high prevalence of primary amenorrhea compared with those with monogenic variation(s).

CONCLUSIONS

The genetic architecture of POI has been enriched through the targeted gene panel in a large cohort of patients with POI. Specific variants in pleiotropic genes may result in isolated POI rather than syndromic POI, whereas oligogenic defects might have cumulative deleterious effects on the severity of POI phenotype.

Ovarian aging: mechanisms and intervention strategies

Ovarian reserve is essential for fertility and influences healthy aging in women. Advanced maternal age correlates with the progressive loss of both the quantity and quality of oocytes. The molecular mechanisms and various contributing factors underlying ovarian aging have been uncovered. In this review, we highlight some of critical factors that impact oocyte quantity and quality during aging. Germ cell and follicle reserve at birth determines reproductive lifespan and timing the menopause in female mammals. Accelerated diminishing ovarian reserve leads to premature ovarian aging or insufficiency. Poor oocyte quality with increasing age could result from chromosomal cohesion deterioration and misaligned chromosomes, telomere shortening, DNA damage and associated genetic mutations, oxidative stress, mitochondrial dysfunction and epigenetic alteration. We also discuss the intervention strategies to delay ovarian aging. Both the efficacy of senotherapies by antioxidants against reproductive aging and mitochondrial therapy are discussed. Functional oocytes and ovarioids could be rejuvenated from pluripotent stem cells or somatic cells. We propose directions for future interventions. As couples increasingly begin delaying parenthood in life worldwide, understanding the molecular mechanisms during female reproductive aging and potential intervention strategies could benefit women in making earlier choices about their reproductive health.

Premature Ovarian Insufficiency in CLPB Deficiency: Transcriptomic, Proteomic and Phenotypic Insights

CONTEXT

Premature ovarian insufficiency (POI) is a common form of female infertility that usually presents as an isolated condition but can be part of various genetic syndromes. Early diagnosis and treatment of POI can minimize comorbidity and improve health outcomes.

OBJECTIVE

We aimed to determine the genetic cause of syndromic POI, intellectual disability, neutropenia, and cataracts.

METHODS

We performed whole-exome sequencing (WES) followed by functional validation via RT-PCR, RNAseq, and quantitative proteomics, as well as clinical update of previously reported patients with variants in the caseinolytic peptidase B (CLPB) gene.

RESULTS

We identified causative variants in CLPB, encoding a mitochondrial disaggregase. Variants in this gene are known to cause an autosomal recessive syndrome involving 3-methylglutaconic aciduria, neurological dysfunction, cataracts, and neutropenia that is often fatal in childhood; however, there is likely a reporting bias toward severe cases. Using RNAseq and quantitative proteomics we validated causation and gained insight into genotype:phenotype correlation. Clinical follow-up of patients with CLPB deficiency who survived to adulthood identified POI and infertility as a common postpubertal ailment.

CONCLUSION

A novel splicing variant is associated with CLPB deficiency in an individual who survived to adulthood. POI is a common feature of postpubertal female individuals with CLPB deficiency. Patients with CLPB deficiency should be referred to pediatric gynecologists/endocrinologists for prompt POI diagnosis and hormone replacement therapy to minimize associated comorbidities.

Genomic testing in premature ovarian insufficiency: proceed with caution

Genomic testing has potential to transform outcomes for women with infertility conditions, such as premature ovarian insufficiency (POI), with growing calls for widespread diagnostic use. The current research literature, however, often uses poor variant curation leading to inflated diagnostic claims and fails to address the complexities of genomic testing for this condition. Without careful execution of the transition from research to the clinic, there is danger of inaccurate diagnoses and poor appreciation of broader implications of testing. This Forum outlines the benefits of genomic testing for POI and raises often-overlooked concerns.

Bilateral Ovarian Germ Cell Tumor in a 46,XX Female with Nijmegen Breakage Syndrome and Hypergonadotropic Hypogonadism

Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disease, affecting mainly patients of Slavic origin. It is caused by a defect in the NBN gene, resulting in defective nibrin protein formation. This leads to chromosomal instability, which predisposes to cancer, with lymphoid malignancies predominating. Nibrin is also involved in gonadal development and its disfunction in females with NBS frequently results in a pure gonadal dysgenesis (PGD) causing hypergonadotropic hypogonadism. However, only a few ovarian tumors in NBS patients have been reported to date. We describe the first case of a girl with NBS with PGD, who developed metachronous bilateral ovarian germ cell tumors (dysgerminoma and gonadoblastoma). Pathogenesis of PGD, neoplastic transformation and therapeutic approach in females with NBS are discussed.

WT1, NR0B1, NR5A1, LHX9, ZFP92, ZNF275, INSL3, and NRIP1 Genetic Variants in Patients with Premature Ovarian Insufficiency in a Mexican Cohort

Premature ovarian insufficiency (POI) is one of the main causes of female premature infertility. POI is a genetically heterogeneous disorder with a complex molecular etiology; as such, the genetic causes remain unknown in the majority of patients. Therefore, this study aimed to identify mutations and characterize the associated molecular contribution of gonadogenesis-determinant genes to POI. Genomic assays, including PCR-SSCP and Sanger sequencing, followed by in silico analyses were used to investigate the underpinnings of ovarian deficiency in 11 women affected by POI. Large deletions and nucleotide insertions and duplications were excluded by PCR. Thirteen genetic variants were identified in the WT1 (c.213G>T, c.609T>C, c.873A>G, c.1122G>A), NR0B1 (c.353C>T, c.425G>A), NR5A1 (c.437G>C, IVS4-20C>T), LHX9 (IVS2-12G>C, IVS3+13C>T, c.741T>C), ZNF275 (c.969C>T), and NRIP1 (c.3403C>T) genes. Seven novel genetic variants and five unpublished substitutions were identified. No genetic aberrations were detected in the ZFP92 and INSL3 genes. Each variant was genotyped using PCR-SSCP in 100 POI-free subjects, and their allelic frequencies were similar to the patients. These analyses indicated that allelic variation in the WT1, NR0B1, NR5A1, LHX9, ZFP92, ZNF275, INSL3, and NRIP1 genes may be a non-disease-causing change or may not contribute significantly to the genetics underlying POI disorders. Findings support the polygenic nature of this clinical disorder, with the SNVs identified representing only a probable contribution to the variability of the human genome.

Whole-exome sequencing reveals new potential genes and variants in patients with premature ovarian insufficiency

PURPOSE

Premature ovarian insufficiency (POI) is a heterogeneous disorder characterized by the cessation of menstrual cycles before the age of 40 years due to the depletion or dysfunction of the ovarian follicles. POI is a highly heterogeneous disease in terms of etiology. The aim of this study is to reveal the genetic etiology in POI patients.

METHODS

A total of 35 patients (mean age: 27.2 years) from 28 different families diagnosed with POI were included in the study. Karyotype, FMR1 premutation analysis, single nucleotide polymorphism (SNP) array, and whole-exome sequencing (WES) were conducted to determine the genetic etiology of patients.

RESULTS

A total of 35 patients with POI were first evaluated by karyotype analysis, and chromosomal anomaly was detected in three (8.5%) and FMR1 premutation was detected in six patients (17%) from two different families. A total of 29 patients without FMR1 premutation were included in the SNP array analysis, and one patient had a 337-kb deletion in the chromosome 6q26 region including PARK2 gene, which was thought to be associated with POI. Twenty-nine cases included in SNP array analysis were evaluated simultaneously with WES analysis, and genetic variant was detected in 55.1% (16/29).

CONCLUSION

In the present study, rare novel variants were identified in genes known to be associated with POI, which contribute to the mutation spectrum. The effects of detected novel genes and variations on different pathways such as gonadal development, meiosis and DNA repair, or metabolism need to be investigated by experimental studies. Molecular etiology allows accurate genetic counseling to the patient and family as well as fertility planning.

Meiotic genes in premature ovarian insufficiency: variants in HROB and REC8 as likely genetic causes

Premature ovarian insufficiency (POI), affecting 1 in 100 women, is characterised by loss of ovarian function associated with elevated gonadotropin, before the age of 40. In addition to infertility, patients face increased risk of comorbidities such as heart disease, osteoporosis, cancer and/or early mortality. We used whole exome sequencing to identify the genetic cause of POI in seven women. Each had biallelic candidate variants in genes with a primary role in DNA damage repair and/or meiosis. This includes two genes, REC8 and HROB, not previously associated with autosomal recessive POI. REC8 encodes a component of the cohesin complex and HROB encodes a factor that recruits MCM8/9 for DNA damage repair. In silico analyses, combined with concordant mouse model phenotypes support these as new genetic causes of POI. We also identified novel variants in MCM8, NUP107, STAG3 and HFM1 and a known variant in POF1B. Our study highlights the pivotal role of meiosis in ovarian function. We identify novel variants, consolidate the pathogenicity of variants previously considered of unknown significance, and propose HROB and REC8 variants as new genetic causes while exploring their link to pathogenesis.

Genetics of ovarian insufficiency and defects of folliculogenesis

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

Targeted whole exome sequencing and Drosophila modelling to unveil the molecular basis of primary ovarian insufficiency

STUDY QUESTION

Can a targeted whole exome sequencing (WES) on a cohort of women showing a primary ovarian insufficiency (POI) phenotype at a young age, combined with a study of copy number variations, identify variants in candidate genes confirming their deleterious effect on ovarian function?

SUMMARY ANSWER

This integrated approach has proved effective in identifying novel candidate genes unveiling mechanisms involved in POI pathogenesis.

WHAT IS KNOWN ALREADY

POI, a condition occurring in 1% of women under 40 years of age, affects women’s fertility leading to a premature loss of ovarian reserve. The genetic causes of POI are highly heterogeneous and several determinants contributing to its prominent oligogenic inheritance pattern still need to be elucidated.

STUDY DESIGN, SIZE, DURATION

WES screening for pathogenic variants of 41 Italian women with non-syndromic primary and early secondary amenorrhoea occurring before age 25 was replicated on another 60 POI patients, including 35 French and 25 American women, to reveal statistically significant shared variants.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The Italian POI patients’ DNA were processed by targeted WES including 542 RefSeq genes expressed or functioning during distinct reproductive or ovarian processes (e.g. DNA repair, meiosis, oocyte maturation, folliculogenesis and menopause). Extremely rare variants were filtered and selected by means of a Fisher Exact test using several publicly available datasets. A case-control Burden test was applied to highlight the most significant genes using two ad-hoc control female cohorts. To support the obtained data, the identified genes were screened on a novel cohort of 60 Caucasian POI patients and the same case-control analysis was carried out. Comparative analysis of the human identified genes was performed on mouse and Drosophila melanogaster by analysing the orthologous genes in their ovarian phenotype, and two of the selected genes were fruit fly modelled to explore their role in fertility.

MAIN RESULTS AND THE ROLE OF CHANCE

The filtering steps applied to search for extremely rare pathogenic variants in the Italian cohort revealed 64 validated single-nucleotide variants/Indels in 59 genes in 30 out of 41 screened women. Burden test analysis highlighted 13 ovarian genes as being the most enriched and significant. To validate these findings, filtering steps and Burden analysis on the second cohort of Caucasian patients yielded 11 significantly enriched genes. Among them, AFP, DMRT3, MOV10, FYN and MYC were significant in both patient cohorts and hence were considered strong candidates for POI. Mouse and Drosophila comparative analysis evaluated a conserved role through the evolution of several candidates, and functional studies using a Drosophila model, when applicable, supported the conserved role of the MOV10 armitage and DMRT3 dmrt93B orthologues in female fertility.

LARGE SCALE DATA

The datasets for the Italian cohort generated during the current study are publicly available at ClinVar database (http://www.ncbi.nlm.nih.gov/clinvar/): accession numbers SCV001364312 to SCV001364375.

LIMITATIONS, REASONS FOR CAUTION

This is a targeted WES analysis hunting variants in candidate genes previously identified by different genomic approaches. For most of the investigated sporadic cases, we could not track the parental inheritance, due to unavailability of the parents’ DNA samples; in addition, we might have overlooked additional rare variants in novel candidate POI genes extracted from the exome data. On the contrary, we might have considered some inherited variants whose clinical significance is uncertain and might not be causative for the patients’ phenotype. Additionally, as regards the Drosophila model, it will be extremely important in the future to have more mutants or RNAi strains available for each candidate gene in order to validate their role in POI pathogenesis.

WIDER IMPLICATIONS OF THE FINDINGS

The genomic, statistical, comparative and functional approaches integrated in our study convincingly support the extremely heterogeneous oligogenic nature of POI, and confirm the maintenance across the evolution of some key genes safeguarding fertility and successful reproduction. Two principal classes of genes were identified: (i) genes primarily involved in meiosis, namely in synaptonemal complex formation, asymmetric division and oocyte maturation and (ii) genes safeguarding cell maintenance (piRNA and DNA repair pathways).

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Italian Ministry of Health grants ‘Ricerca Corrente’ (08C621_2016 and 08C924_2019) provided to IRCCS Istituto Auxologico Italiano, and by ‘Piano Sostegno alla Ricerca’ (PSR2020_FINELLI_LINEA_B) provided by the University of Milan; M.P.B. was supported by Telethon-Italy (grant number GG14181). There are no conflicts of interest.

Compound heterozygous null mutations of NOBOX in sisters with delayed puberty and primary amenorrhea

Background

Premature ovarian insufficiency (POI) is a heterogeneous clinical syndrome defined by a premature loss of ovarian function that associates menstrual disturbances and hypergonatropic hypogonadism. POI is a major cause of female infertility affecting 1% of women before the age of 40 and up to 0.01% before the age of 20. The etiology of POI may be iatrogenic, auto‐immune or genetic but remains however undetermined in a large majority of cases. An underlying genetic etiology has to be searched in idiopathic cases, particularly in the context of a family history of POI.

Methods

Whole exome sequencing (WES) was performed in trio in a Belgian patient presenting POI and in her two parents. The patient presented delayed puberty and primary amenorrhea with hypergonadotropic hypogonadism.

Results

WES identified two novel compound heterozygous truncating mutations in the Newborn oogenesis homeobox (NOBOX) gene, c.826C>T (p.(Arg276Ter)) and c.1421del (p.(Gly474AlafsTer76)). Both mutations were confirmed by Sanger sequencing in the proband's sister who presented the same phenotype. Both variants were pathogenic and very likely responsible for the severe POI in this family.

Conclusion

We report here for the first time compound heterozygous truncating mutations of NOBOX in outbred patients, generalizing biallelic NOBOX null mutations as a cause of severe POI with primary amenorrhea. In addition, our findings also suggest that NOBOX haploinsufficiency is tolerated.

Searching for female reproductive aging and longevity biomarkers

Female reproductive aging is, in a way, a biological phenomenon that develops along canonical molecular pathways; however, it has particular features. Recent studies revealed complexity of the interconnections between reproductive aging and aging of other systems, and even suggested a cause-effect uncertainty between them. It was also shown that reproductive aging can impact aging processes in an organism at the level of cells, tissues, organs, and systems. Women at the end of their reproductive lives are characterized by the accelerated incidence of age-related diseases. Timing of the onset of menarche and menopause and variability in the duration of reproductive life carry a latent social risk: not having enough information about the reproductive potential, women keep on postponing childbirth. Identification and use of the most accurate and sensitive aging biomarkers enable the prediction of menopause timing and quantification of the true biological and reproductive ages of an organism. We discuss current views on reproductive aging and peculiarities of using available biomarkers of aging. We also consider latest advances in the search for potential genetic markers of reproductive aging. Finally, we posit the importance of determining the female biological age and highlight potential research directions in this area.

Premature Ovarian Insufficiency: Past, Present, and Future

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

Meiosis interrupted: the genetics of female infertility via meiotic failure

Idiopathic or 'unexplained' infertility represents as many as 30% of infertility cases worldwide. Conception, implantation, and term delivery of developmentally healthy infants require chromosomally normal (euploid) eggs and sperm. The crux of euploid egg production is error-free meiosis. Pathologic genetic variants dysregulate meiotic processes that occur during prophase I, meiotic resumption, chromosome segregation, and in cell cycle regulation. This dysregulation can result in chromosomally abnormal (aneuploid) eggs. In turn, egg aneuploidy leads to a broad range of clinical infertility phenotypes, including primary ovarian insufficiency and early menopause, egg fertilization failure and embryonic developmental arrest, or recurrent pregnancy loss. Therefore, maternal genetic variants are emerging as infertility biomarkers, which could allow informed reproductive decision-making. Here, we select and deeply examine human genetic variants that likely cause dysregulation of critical meiotic processes in 14 female infertility-associated genes: SYCP3, SYCE1, TRIP13, PSMC3IP, DMC1, MCM8, MCM9, STAG3, PATL2, TUBB8, CEP120, AURKB, AURKC, andWEE2. We discuss the function of each gene in meiosis, explore genotype-phenotype relationships, and delineate the frequencies of infertility-associated variants.

Isoform-Specific Roles of Mutant p63 in Human Diseases

Simple Summary

The protein p63 belongs to the family of the p53 tumor suppressor. Mouse models have, however, shown that it is not a classical tumor suppressor but instead involved in developmental processes. Mutations in the p63 gene cause several developmental defects in human patients characterized by limb deformation, cleft lip/palate, and ectodermal dysplasia due to p63’s role as a master regulator of epidermal development. In addition, p63 plays a key role as a quality control factor in oocytes and p63 mutations can result either in compromised genetic quality control or premature cell death of all oocytes.

Abstract

The p63 gene encodes a master regulator of epidermal commitment, development, and differentiation. Heterozygous mutations in the DNA binding domain cause Ectrodactyly, Ectodermal Dysplasia, characterized by limb deformation, cleft lip/palate, and ectodermal dysplasia while mutations in in the C-terminal domain of the α-isoform cause Ankyloblepharon-Ectodermal defects-Cleft lip/palate (AEC) syndrome, a life-threatening disorder characterized by skin fragility, severe, long-lasting skin erosions, and cleft lip/palate. The molecular disease mechanisms of these syndromes have recently become elucidated and have enhanced our understanding of the role of p63 in epidermal development. Here we review the molecular cause and functional consequences of these p63-mutations for skin development and discuss the consequences of p63 mutations for female fertility.

The p63 C-terminus is essential for murine oocyte integrity

The transcription factor p63 mediates distinct cellular responses, primarily regulating epithelial and oocyte biology. In addition to the two amino terminal isoforms, TAp63 and ΔNp63, the 3'-end of p63 mRNA undergoes tissue-specific alternative splicing that leads to several isoforms, including p63α, p63β and p63γ. To investigate in vivo how the different isoforms fulfil distinct functions at the cellular and developmental levels, we developed a mouse model replacing the p63α with p63β by deletion of exon 13 in the Trp63 gene. Here, we report that whereas in two organs physiologically expressing p63α, such as thymus and skin, no abnormalities are detected, total infertility is evident in heterozygous female mice. A sharp reduction in the number of primary oocytes during the first week after birth occurs as a consequence of the enhanced expression of the pro-apoptotic transcriptional targets Puma and Noxa by the tetrameric, constitutively active, TAp63β isoform. Hence, these mice show a condition of ovary dysfunction, resembling human primary ovary insufficiency. Our results show that the p63 C-terminus is essential in TAp63α-expressing primary oocytes to control cell death in vivo, expanding the current understanding of human primary ovarian insufficiency.

DNA Damaged Induced Cell Death in Oocytes

The production of haploid gametes through meiosis is central to the principle of sexual reproduction. The genetic diversity is further enhanced by exchange of genetic material between homologous chromosomes by the crossover mechanism. This mechanism not only requires correct pairing of homologous chromosomes but also efficient repair of the induced DNA double-strand breaks. Oocytes have evolved a unique quality control system that eliminates cells if chromosomes do not correctly align or if DNA repair is not possible. Central to this monitoring system that is conserved from nematodes and fruit fly to humans is the p53 protein family, and in vertebrates in particular p63. In mammals, oocytes are stored for a long time in the prophase of meiosis I which, in humans, can last more than 50 years. During the entire time of this arrest phase, the DNA damage checkpoint remains active. The treatment of female cancer patients with DNA damaging irradiation or chemotherapeutics activates this checkpoint and results in elimination of the oocyte pool causing premature menopause and infertility. Here, we review the molecular mechanisms of this quality control system and discuss potential therapeutic intervention for the preservation of the oocyte pool during chemotherapy.

Whole-exome sequencing in patients with premature ovarian insufficiency: early detection and early intervention

Background

The loss of ovarian function in women, referred to as premature ovarian insufficiency (POI), is associated with a series of concomitant diseases. POI is genetically heterogeneous, and in most cases, the etiology is unknown.

Methods

Whole-exome sequencing (WES) was performed on DNA samples obtained from patients with POI, and Sanger sequencing was used to validate the detected potentially pathogenic variants. An in silico analysis was carried out to predict the pathogenicity of the variants.

Results

We recruited 24 patients with POI and identified variants in POI-related genes in 14 patients, including bi-allelic mutations in DNAH6, HFM1, EIF2B2, BNC, and LRPPRC and heterozygous variants in BNC1, EIF2B4, FOXL2, MCM9, FANCA, ATM, EIF2B3, and GHR. No variants in the above genes were detected in the WES data obtained from 29 women in a control group without POI. Determining a clear genetic etiology could significantly increase patient compliance with appropriate intervention strategies.

Conclusions

Our study confirmed that POI is a genetically heterogeneous condition and that whole-exome sequencing is a powerful tool for determining its genetic etiology. The results of this study will aid researchers and clinicians in genetic counseling and suggests the potential of WES for the detection of POI and thus early interventions for patients with POI.

A missense in HSF2BP causing primary ovarian insufficiency affects meiotic recombination by its novel interactor C19ORF57/BRME1

Primary Ovarian Insufficiency (POI) is a major cause of infertility, but its etiology remains poorly understood. Using whole-exome sequencing in a family with three cases of POI, we identified the candidate missense variant S167L in HSF2BP, an essential meiotic gene. Functional analysis of the HSF2BP-S167L variant in mouse showed that it behaves as a hypomorphic allele compared to a new loss-of-function (knock-out) mouse model. Hsf2bpS167L/S167L females show reduced fertility with smaller litter sizes. To obtain mechanistic insights, we identified C19ORF57/BRME1 as a strong interactor and stabilizer of HSF2BP and showed that the BRME1/HSF2BP protein complex co-immunoprecipitates with BRCA2, RAD51, RPA and PALB2. Meiocytes bearing the HSF2BP-S167L variant showed a strongly decreased staining of both HSF2BP and BRME1 at the recombination nodules and a reduced number of the foci formed by the recombinases RAD51/DMC1, thus leading to a lower frequency of crossovers. Our results provide insights into the molecular mechanism of HSF2BP-S167L in human ovarian insufficiency and sub(in)fertility.

Novel inactivating follicle-stimulating hormone receptor mutations in a patient with premature ovarian insufficiency identified by next-generation sequencing gene panel analysis

Objective

To find the genetic etiology of premature ovarian insufficiency (POI) in a patient with primary amenorrhea and hypergonadotropic hypogonadism.

Design

Case report.

Setting

University hospital.

Patient(s)

A Belgian woman aged 32 years with POI at the age of 17, her parents, and her sister whose POI was diagnosed at age 29.

Intervention(s)

Analysis of a panel of 31 genes implicated in POI (POIGP) using next-generation sequencing (NGS), Sanger sequencing, and in vitro functional study.

Main Outcome Measure(s)

Gene variants, family mutational segregation, and in vitro functional impact of the mutant proteins.

Result(s)

The analysis of the gene panel using NGS identified the presence of two novel follicle-stimulating hormone receptor (FSHR) missense mutations at a compound heterozygous state in the affected patient: c.646 G>A, p.Gly216Arg, and c.1313C>T, p.Thr438Ile. Sanger sequencing showed the presence of each mutation at heterozygous state in the patient’s parents and at heterozygous compound state in the affected sister. Both substituted amino acids (Gly216 and Thr438) were conserved in FSHR of several vertebrate species as well as in other glycoproteins receptors (TSHR and LHCGHR), suggesting a potentially important role in glycoprotein receptor function. An in vitro functional study showed similar results for both variants with more than 90% reduction of their cell surface expression and a 55% reduction of their FSH-induced cyclic adenosine 3′:5′ monophosphate (cAMP) production compared with the wild-type FSHR.

Conclusion(s)

The analysis of a gene panel of 31 genes implicated in POI allowed us to identify two novel partially inactivating mutations of FSHR that are likely responsible for the POI phenotype of the proband and of her affected sister.

Genetics of Primary Ovarian Insufficiency in the Next-Generation Sequencing Era

Primary ovarian insufficiency (POI) is characterized by amenorrhea, increased follicle-stimulating hormone (FSH) levels, and hypoestrogenism, leading to infertility before the age of 40 years. Elucidating the cause of POI is a key point for diagnosing and treating affected women. Here, we review the genetic etiology of POI, highlighting new genes identified in the last few years using next-generation sequencing (NGS) approaches. We searched the MEDLINE/PubMed, Cochrane, and Web of Science databases for articles published in or translated to English. Several genes were found to be associated with POI genetic etiology in humans and animal models (SPIDR, BMPR2, MSH4, MSH5, GJA4, FANCM, POLR2C, MRPS22, KHDRBS1, BNC1, WDR62, ATG7/ATG9, BRCA2, NOTCH2, POLR3H, and TP63). The heterogeneity of POI etiology has been revealed to be remarkable in the NGS era, and discoveries have indicated that meiosis and DNA repair play key roles in POI development.

DNA repair functional analyses of NBN hypomorphic variants associated with NBN-related infertility

Nijmegen breakage syndrome caused by biallelic pathogenic variants of the DNA-damage response gene NBN, is characterized by severe microcephaly, cancer proneness, infertility, and karyotype abnormalities. We previously reported NBN variants in siblings suffering from fertility defects. Here, we identify a new founder NBN variant (c.442A>G, p.(Thr148Ala)) in Lebanese patients associated with isolated infertility. Functional analyses explored preserved or altered functions correlated with their remarkably mild phenotype. Transcript and protein analyses supported the use of an alternative transcript with in-frame skipping of exons 4-5, leading to p84-NBN protein with a preserved forkhead-associated (FHA) domain. The level of NBN was dramatically reduced and the MRN complex delocalized to the cytoplasm. Interestingly, ataxia-elangiectasia mutated (ATM) also shifted from the nucleus to the cytoplasm, suggesting some interaction between ATM and the MRN complex at a steady state. The ATM pathway activation, attenuated in typical patients with NBS, appeared normal under camptothecin treatment in these new NBN-related infertile patients. Cell cycle checkpoint defect was present in these atypical patients, although to a lesser extent than in typical patients with NBS. In conclusion, we report three new NBN-related infertile patients and we suggest that preserved FHA domain could be responsible for the mild phenotype and intermediate DNA-damage response defects.

Functional evidence implicating NOTCH2 missense mutations in primary ovarian insufficiency etiology

Primary ovarian insufficiency (POI) is a frequently occurring disease affecting women under 40 years old. Recently, we have analyzed unrelated POI women via whole exome sequencing (WES) and identified NOTCH2 mutations underlying possible functional effects. The present study involved reanalyzing of WES assays. We used in the KGN granulosa-like cell model, a synthetic gene reporter construct driving luciferase gene expression to assess the functional effects of five NOTCH2 mutations identified in POI patients. We found that NOTCH2-p.Ser1804Leu, p.Ala2316Val, and p.Pro2359Ala mutations had a functional impact on the protein's transcriptional activity. The results have demonstrated for the first time that NOTCH2 mutations contribute to POI etiology. We therefore recommend sequencing NOTCH2's open reading frame in large panels of POI patients to establish an accurate genotype-phenotype correlation. We cannot rule out the fact that patients affected by Alagille syndrome carrying NOTCH2 mutations may suffer ovarian dysfunction.