Zi-Jiang Chen

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.

Age-specific serum antimüllerian hormone levels in women with and without polycystic ovary syndrome

OBJECTIVE To determine the serum antimüllerian hormone (AMH) reference values in Chinese women with and without polycystic ovary syndrome (PCOS), and the associations of AMH with clinical or biochemical characteristics. DESIGN Retrospective study. SETTING Academic institutions. PATIENT(S) Totals of 1,896 infertile control women and 304 women with PCOS. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Serum basal AMH levels and clinical, endocrine, and metabolic parameters. RESULT(S) In the same age group, serum AMH levels were higher in PCOS women than those without PCOS. AMH levels were not significantly related to indices of insulin resistance or metabolic-related variables in both groups. In the infertile control group, AMH increased with antral follicle count (AFC) and LH and decreased with age, body mass index (BMI), and FSH. In the PCOS group, AMH levels showed positive correlations with LH, AFC, and T and negative correlations with BMI. The median AMH levels were 2.35 ng/mL for ages 20-31 years, 1.58 ng/mL for ages 32-34 years, 1.30 ng/mL for ages 35-37 years, 0.96 ng/mL for ages 38-40 years, 1.05 ng/mL for ages 41-43 years, and 0.67 ng/mL for ages>43 years in the control group and 4.38 ng/mL for ages 20-31 years, 3.47 ng/mL for ages 32-34 years, and 3.30 ng/mL for ages 35-37 years in the PCOS group. CONCLUSION(S) This study determined reference values of serum AMH in Chinese women with and without PCOS. Elevated serum AMH levels do not affect the risk of insulin resistance or metabolic syndrome.

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.

Association Study between Polycystic Ovarian Syndrome and the Susceptibility Genes Polymorphisms in Hui Chinese Women

Introduction Polycystic ovary syndrome (PCOS) is one of the most common endocrine-metabolic disorders. Evidence of familial aggregation analysis and different clinical traits among different regions and ethnicities indicated that the pathogenesis of PCOS is associated with multiple genetic and environmental factors. Our previous research had identified three susceptibility loci (rs2479106, DENND1A; rs13405728, LHCGR; rs13429458, THADA) for PCOS in Han Chinese women. The overall aim of this study was to investigate the relationship between three susceptibility gene polymorphisms and PCOS in Hui ethnic women. Methods 151 patients with PCOS (case group) and 99 healthy women (control group) were recruited from the Reproductive Medicine Center of the General Hospital of Ningxia Medical University. Clinical data and serum hormone characteristics of case and control groups were collected and analyzed. The three susceptibility single-nucleotide polymorphisms have been replicated in both case and control groups. Gene polymorphisms were detected by direct sequencing after polymerase chain reaction. Results The Body Mass Index, LH, LH/FSH ratio and total testosterone were significantly elevated in PCOS patients compared to control group (P<0.05). The frequencies of genotype and allele in rs13405728 were significantly different between the PCOS and the control groups (P<0.05). Of the SNP rs13405728, the PCOS cases with TT genotype stayed at a higher level of total testosterone, TG and LDL than those with the CC and CT genotypes. In contrary, there was no statistical difference between the two groups for SNP rs13429458 and rs2479106 (P>0.05). Conclusion The present study suggested that the SNP rs13405728 in the LHCGR gene was associated with PCOS in Hui ethnic women, and its TT genotype characterized with higher level of TT, TG and LDL.

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.

Melatonin levels in follicular fluid as markers for IVF outcomes and predicting ovarian reserve

Good-quality oocytes are critical for the success of in vitro fertilization (IVF), but, to date, there is no marker of ovarian reserve available that can accurately predict oocyte quality. Melatonin exerts its antioxidant actions as a strong radical scavenger that might affect oocyte quality directly as it is the most potent antioxidant in follicular fluid. To investigate the precise role of endogenous melatonin in IVF outcomes, we recruited 61 women undergoing treatment cycles of IVF or intracytoplasmic sperm injection (ICSI) procedures and classified them into three groups according to their response to ovarian stimulation. Follicular fluid was collected to assess melatonin levels using a direct RIA method. We found good correlations between melatonin levels in follicular fluid with age, anti-Müllerian hormone (AMH) and baseline follicle-stimulating hormone (bFSH), all of which have been used to predict ovarian reserve. Furthermore, as melatonin levels correlated to IVF outcomes, higher numbers of oocytes were collected from patients with higher melatonin levels and consequently the number of oocytes fertilized, zygotes cleaved, top quality embryos on D3, blastocysts obtained and embryos suitable for transplantation was higher. The blastocyst rate increased in concert with the melatonin levels across the gradient between the poor response group and the high response group. These results demonstrated that the melatonin levels in follicular fluid is associated with both the quantity and quality of oocytes and can predict IVF outcomes as well making them highly relevant biochemical markers of ovarian reserve.

Bisphenol A and Ovarian Reserve among Infertile Women with Polycystic Ovarian Syndrome

To better understand possible effects of bisphenol A (BPA) exposure on ovarian reserve in women with polycystic ovary syndrome (PCOS), we measured creatinine adjusted urinary BPA (BPA_Cre) concentrations and used regression models to evaluate the association between urinary BPA level and antral follicle count (AFC), antimullerian hormone (AMH), day-3 follicle stimulating hormone levels (FSH) and inhibin B (INHB) in 268 infertile women diagnosed with PCOS. BPA was detected in all women with a median concentration of 2.35 ng/mL (the 25th and 75th percentiles of 1.47 ng/mL and 3.95 ng/mL). A unit increase in BPA_Cre was associated with a significant decrease of 0.34 in AFC (β = −0.34, 95% CI = −0.60, −0.08; p = 0.01). Likewise, BPA was negatively associated with AMH and day-3 FSH levels, but neither of them reached statistical significance. No association was observed between BPA and INHB. Our results suggest that in women with PCOS, BPA may affect ovarian follicles and, therefore, reduce ovarian reserve.