Xue Jiao

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.

Novel variants in the SOHLH2 gene are implicated in human premature ovarian failure

OBJECTIVE To determine whether variants in the SOHLH2 gene contribute to human premature ovarian failure (POF) in different ethnicities. DESIGN Case-control genetic study. SETTING University hospitals. PATIENT(S) Chinese (364 cases) and Serbian (197 cases) women with nonsyndromic POF and ethnically matched controls. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Variation analysis of the SOHLH2 gene. RESULT(S) Eleven novel heterozygous variants were identified in cohorts of POF but were absent in matched controls. These included the nonsynonymous variants p.Glu79Lys (n = 2 cases), p.Glu105Gly, and p.Thr321Pro, which were found among four Chinese POF cases, and p.Leu120Phe (n = 3 cases) and p.Leu204Phe, which were found among four Serbian women. Protein alignments reveal that p.Glu79Lys and p.Glu105Gly involve amino acids highly conserved among mammals, both of which are predicted to be deleterious. The c.-210G>T found in the Chinese POF cohort lies in the core promoter region, which is enriched with transcription factor binding sites and CpG islands. In the Serbian cohort, the variant most likely to have a deleterious effect is c.530+6T>G, which is predicted to affect RNA splicing and result in nonsense mediated decay of transcripts. The other variants are less likely to be deleterious. Disturbing the expression, transactivation or homo-/ heterodimerization of the SOHLH2 protein could result in ovarian failure. Overall, four of the 11 novel variants seem plausible explanations for POF; the other seven variants are less likely but cannot be categorically excluded. CONCLUSION(S) Our identification of novel variants in the SOHLH2 gene, in women with POF of both Chinese and Serbian origin, strongly suggests an important role for SOHLH2 in human POF etiology.

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.

Novel NR5A1 missense mutation in premature ovarian failure: detection in han chinese indicates causation in different ethnic groups.

Background The etiology of most premature ovarian failure (POF) cases is usually elusive. Although genetic causes clearly exist and a likely susceptible region of 8q22.3 has been discovered, no predominant explanation exists for POF. More recently, evidences have indicated that mutations in NR5A1 gene could be causative for POF. We therefore screened for mutations in the NR5A1 gene in a large cohort of Chinese women with non-syndromic POF. Methods Mutation screening of NR5A1 gene was performed in 400 Han Chinese women with well-defined 46,XX idiopathic non-syndromic POF and 400 controls. Subsequently, functional characterization of the novel mutation identified was evaluated in vitro. Results A novel heterozygous missense mutation [c.13T>G (p.Tyr5Asp)] in NR5A1 was identified in 1 of 384 patients (0.26%). This mutation impaired transcriptional activation on Amh, Inhibin-a, Cyp11a1 and Cyp19a1 gene, as shown by transactivation assays. However, no dominant negative effect was observed, nor was there impact on protein expression and nuclear localization. Conclusions This novel mutation p.Tyr5Asp, in a novel non-domain region, is presumed to result in haploinsufficiency. Irrespectively, perturbation in NR5A1 is not a common explanation for POF in Chinese.

Mutations in MSH5 in primary ovarian insufficiency

Abstract Primary ovarian insufficiency (POI) is a genetically heterogeneous disorder that occurs in familial or sporadic fashion. Through whole exome sequencing in a Chinese pedigree with POI, we identified a novel homozygous missense mutation (ENST00000375755: c.1459G > T, p.D487Y) in the MSH5 gene in two sisters with POI. The homologous mutation in mice resulted in atrophic ovaries without oocytes, and in vitro functional study revealed that mutant MSH5 impaired DNA homologous recombination repair. From sanger sequencing of MSH5 in 200 sporadic POI patients, we identified three heterozygous mutations (ENST00000375755: c.1057C > A, p.L353M; c.1459G > T, p.D487Y and c.2107 A > G, p.I703V). Considering the heterozygous p.D487Y carrier in the POI pedigree was fertile, the causality of the three heterozygous mutations in POI need more evidence. Our studies confirmed that perturbation of genes involved in DNA damage repair could lead to non-syndromic POI. The underlying mechanism-inability to repair DNA damage-will receive increasing attention with respect to POI.

FMR1 premutation is an uncommon explanation for premature ovarian failure in Han Chinese.

Background In premature ovarian failure (POF), cessation of menstruation occurs before the expected age of menopause. Approximately 1% of women are affected. FMR1 premutation was reported to be responsible for up to 3.3%–6.7% of sporadic POF and 13% of familial cases in Caucasians, while the data was absent in Chinese population. Therefore, the impact of FMR1 CGG repeat on ovarian reserve is needed to be investigated in large Chinese cohort. Methods The number of FMR1 CGG repeat was determined in 379 Han Chinese women with well-defined 46, XX non-syndromic sporadic POF and 402 controls. The age of menopause onset in respect to CGG repeats was further analyzed. Results The frequency of FMR1 premutation in Han Chinese POF was only 0.5% (2/379), although it was higher than that in matched controls (0%, 0/402), it was much lower than that reported in Caucasian with POF (3.3%–6.7%). The prevalence of intermediate FMR1 (41–54) was not increased significantly in sporadic POF than that in controls (2.9% vs. 1.7%, P = 0.343). However, POF patients more often carried a single additional CGG repeat in a single allele than did fertile women (allele-1: 29.7 vs. 28.8, P<0.001; allele-2: 32.6 vs. 31.5, P<0.001). POF patients with both alleles of CGG repeats outside (below or above) the normal range (26–34) showed an earlier age of cessation of menses than those with two alleles within normal range (hom-high/high vs. norm: 20.4±4.8 vs. 24.7±6.4, p<0.01; hom-low/high vs. norm: 18.7±1.7 vs. 24.7±6.4, p<0.01). Conclusions FMR1 premutation seems to be an uncommon explanation for POF in Han Chinese. However, having both alleles with CGG repeats outside the normal range might still adversely affect ovarian aging.

Premature Ovarian Insufficiency: Phenotypic Characterization Within Different Etiologies

Context Premature ovarian insufficiency (POI) is highly heterogeneous, both in phenotype and etiology. They are not yet clearly stated and correlated. Objective To characterize clinical presentations of a large, well-phenotyped cohort of women with POI, and correlate phenotypes with etiologies to draw a comprehensive clinical picture of POI. Design, Patients, Interventions, and Main Outcome Measures In this retrospective study, a total of 955 Chinese women with overt POI between 2006 and 2015 were systemically evaluated and analyzed. The phenotypic features, including menstrual characteristics, hormone profiles, ovarian ultrasonography/biopsy, pregnancy/family history, and genetic/autoimmune/iatrogenic etiologies were assessed and further compared within different subgroups. Results Among 955 women with POI, 85.97% presented with secondary amenorrhea (SA) and 14.03% with primary amenorrhea (PA). PA represented the most severe ovarian dysfunction and more chromosomal aberrations than SA. The decline of ovarian function in patients with SA progressed quickly. They had shortened reproductive periods (approximately 10 years) and developed amenorrhea within 1 to 2 years after menstrual irregularity. The ovaries were invisible or small, and the presence of follicles (28.43%) was correlated with other good reproductive indicators. Familial patients (12.25%) manifested better ovarian status and fewer chromosomal aberrations than sporadic patients. The etiologies consisted of genetic (13.15%), autoimmune (12.04%), and iatrogenic (7.29%), approximately 68% remaining idiopathic. There were significant differences among different etiologies, with the genetic group representing the most severe phenotype. Conclusion Our results regarding distinct phenotypic characteristics and association with different etiologies further confirmed the high heterogeneity of POI. Additional longitudinal clinical studies and pathogenesis research are warranted.

Identification of patients with primary ovarian insufficiency caused by autoimmunity

Autoimmune pathogenesis is responsible for a subset of primary ovarian insufficiency (POI) cases. The significance of autoantibodies for POI, however, remains unclear. A total of 250 women with idiopathic POI and 256 age-matched healthy women were enrolled. The presence in serum of adrenal cortex autoantibody (AAA), detected by indirect immunofluorescence and non-organ-specific antibodies, including antinuclear antibody, anti-cardiolipin antibody, and anti-double stranded DNA antibody, detected by enzyme-linked immunosorbent assay, was compared. Ovarian biopsy was carried out for histology assessment. Adrenal function was followed-up in 15 women with POI who were positive for AAA. Higher frequency of positive AAA was observed in women with POI (19.2%) compared with controls (5.9%, P < 0.01). No difference in anti-cardiolipin antibody, antinuclear antibody and anti-double stranded DNA antibody was found between the two groups. Ovarian biopsies in 13 women with POI (six AAA positive and seven negative) showed atrophic ovaries devoid of follicles. One out of fifteen women positive for AAA had symptoms of adrenal insufficiency 3 years after POI diagnosis. Significantly higher positive frequency of AAA in POI patients suggests the role of autoimmune disturbance in pathogenesis. Therefore, AAA may serve as a biomarker for ovarian autoimmunity.

Molecular Genetics of Premature Ovarian Insufficiency

Premature ovarian insufficiency (POI) is highly heterogeneous in genetic etiology. Yet identifying causative genes has been challenging with candidate gene approaches. Recent approaches using next generation sequencing (NGS), especially whole exome sequencing (WES), in large POI pedigrees have identified new causatives and proposed relevant candidates, mainly enriched in DNA damage repair, homologous recombination, and meiosis. In the near future, NGS or whole genome sequencing will help better define genes involved in intricate regulatory networks. The research into miRNA and age at menopause represents an emerging field that will help unveil the molecular mechanisms underlying pathogenesis of POI. Shedding light on the genetic architecture is important in interpreting pathogenesis of POI, and will facilitate risk prediction for POI.

CAV1 regulates primordial follicle formation via the Notch2 signalling pathway and is associated with premature ovarian insufficiency in humans

STUDY QUESTION What is the function of CAV1 in folliculogenesis and female reproduction? SUMMARY ANSWER CAV1 regulates germline cyst breakdown and primordial follicle (PF) formation in mice, and CAV1 mutation may be related to premature ovarian insufficiency (POI). WHAT IS KNOWN ALREADY Pre-granulosa cells are essential for the establishment of the PF pool, which determines female fertility and reproductive lifespan. Cav1 participates in vascularization in fetal mouse ovaries. However, the role of CAV1 in early folliculogenesis and POI pathogenesis remains unclear. STUDY DESIGN, SIZE, DURATION Cav1 function was investigated in mice and Human Embryonic Kidney 293 cells. Ovaries (six per group) were randomly assigned to Cav1-vivo-morpholino, control and control-morpholino groups, and all experiments were repeated at least three times. To investigate CAV1 mutations in women, 200 Chinese women with POI and 200 control individuals with regular menstrual cycles and normal endocrine profiles were recruited from the Center for Reproductive Medicine of Shandong University between September 2012 and December 2013. PARTICIPANTS/MATERIALS, SETTING, METHODS Wild-type CD1 mice, Lgr5-EGFP-ires-CreERT2 (Lgr5-KI) reporter mice and Human Embryonic Kidney 293 cells were used for these experiments. Protein expression was detected by Western blot, and quantitative RT-PCR was used to detect gene expression. The expression pattern of CAV1 in mouse ovaries and the phenotype of Cav1 deficiency in mice were detected by immunofluorescence. Pre-granulosa cell proliferation in ovaries was detected by bromodeoxyuridine (BrdU) assay and immunofluorescence. The coding region of the CAV1 gene was sequenced in 200 women with POI and 200 controls. The functional effect of the novel mutation c.142 G > C (p.Glu48Gln) was investigated by Cell Counting Kit-8 (CCK8) assays and Western blot. MAIN RESULTS AND THE ROLE OF CHANCE We confirmed that Cav1 deficiency in mouse ovary induced by CAV1-vivo-morpholino resulted in more multi-oocyte follicles than in the control and control-morpholino groups (P < 0.01). Suppression of Cav1 decreased Leucine rich repeat containing G protein coupled receptor 5 (Lgr5)-positive cell proliferation (P < 0.01) and reduced the number of Lgr5 and Forkhead box L2 (Foxl2) double-positive cells (P < 0.01). Furthermore, suppression of Cav1 inhibited ovarian epithelial Lgr5-positive cell proliferation and differentiation through the Notch2 signalling pathway. Two of the POI women carried novel CAV1 mutations (c.45 C > G synonymous and c.142 G > C [Glu48Gln]). The deleterious effect of p.Glu48Gln was corroborated by showing that it adversely affected the function of CAV1 in cell proliferation and NOTCH2 expression in HEK293FT cells. LARGE-SCALE DATA N/A. LIMITATIONS, REASONS FOR CAUTION The novel Glu48Gln mutation was only detected in one of 200 POI patients and we were unable to investigate its effects in the ovary. WIDER IMPLICATIONS OF THE FINDINGS The identification of CAV1 as a potentially causative gene for POI provides a theoretical basis to devise treatments for POI in women. STUDY FUNDING/COMPETING INTEREST(S) This work was supported by the National Basic Research Program of China (973 Programs: 2012CB944700; 2013CB945501; 2013CB911400; 2014CB943202), the National Key Research and Development Program of China (2016YFC1000604, 2017YFC1001301), the State Key Program of National Natural Science Foundation of China (81430029), and the National Natural Science Foundation of China (31571540, 81522018, 81471509, 81601245, 81701406, 81571406). The authors declare no competing financial interests.