MCM8 interacts with DDX5 to promote R-loop resolution.

MCM8 has emerged as a core gene in reproductive aging and is crucial for meiotic homologous recombination repair. It also safeguards genome stability by coordinating the replication stress response during mitosis, but its function in mitotic germ cells remains elusive. Here we found that disabling MCM8 in mice resulted in proliferation defects of primordial germ cells (PGCs) and ultimately impaired fertility. We further demonstrated that MCM8 interacted with two known helicases DDX5 and DHX9, and loss of MCM8 led to R-loop accumulation by reducing the retention of these helicases at R-loops, thus inducing genome instability. Cells expressing premature ovarian insufficiency-causative mutants of MCM8 with decreased interaction with DDX5 displayed increased R-loop levels. These results show MCM8 interacts with R-loop-resolving factors to prevent R-loop-induced DNA damage, which may contribute to the maintenance of genome integrity of PGCs and reproductive reserve establishment. Our findings thus reveal an essential role for MCM8 in PGC development and improve our understanding of reproductive aging caused by genome instability in mitotic germ cells.

Transcription-replication conflicts in primordial germ cells necessitate the Fanconi anemia pathway to safeguard genome stability.

Preserving a high degree of genome integrity and stability in germ cells is of utmost importance for reproduction and species propagation. However, the regulatory mechanisms of maintaining genome stability in the developing primordial germ cells (PGCs), in which rapid proliferation is coupled with global hypertranscription, remain largely unknown. Here, we find that mouse PGCs encounter a constitutively high frequency of transcription-replication conflicts (TRCs), which lead to R-loop accumulation and impose endogenous replication stress on PGCs. We further demonstrate that the Fanconi anemia (FA) pathway is activated by TRCs and has a central role in the coordination between replication and transcription in the rapidly proliferating PGCs, as disabling the FA pathway leads to TRC and R-loop accumulation, replication fork destabilization, increased DNA damage, dramatic loss of mitotically dividing mouse PGCs, and consequent sterility of both sexes. Overall, our findings uncover the unique source and resolving mechanism of endogenous replication stress during PGC proliferation, provide a biological explanation for reproductive defects in individuals with FA, and improve our understanding of the monitoring strategies for genome stability during germ cell development.

DNA repair protein FANCD2 has both ubiquitination-dependent and ubiquitination-independent functions during germ cell development.

When DNA interstrand crosslink lesions occur, a core complex of Fanconi anemia proteins promotes the ubiquitination of FANCD2 and FANCI, which recruit downstream factors to repair the lesion. However, FANCD2 maintains genome stability not only through its ubiquitination-dependent but also its ubiquitination-independent functions in various DNA damage response pathways. Increasing evidence suggests that FANCD2 is essential for fertility, but its ubiquitination-dependent and ubiquitination-independent roles during germ cell development are not well characterized. In this study, we analyzed germ cell development in Fancd2 KO and ubiquitination-deficient mutant (Fancd2K559R/K559R) mice. We showed that in the embryonic stage, both the ubiquitination-dependent and ubiquitination-independent functions of FANCD2 were required for the expansion of primordial germ cells and establishment of the reproductive reserve by reducing transcription-replication conflicts and thus maintaining genome stability in primordial germ cells. Furthermore, we found that during meiosis in spermatogenesis, FANCD2 promoted chromosome synapsis and regulated crossover formation independently of its ubiquitination, but that both ubiquitinated and nonubiquitinated FANCD2 functioned in programmed double strand break repair. Finally, we revealed that on meiotic XY chromosomes, H3K4me2 accumulation required ubiquitination-independent functionality of FANCD2, while the regulation of H3K9me2 and H3K9me3 depended on FANCD2 ubiquitination. Taken together, our findings suggest that FANCD2 has distinct functions that are both dependent on and independent of its ubiquitination during germ cell development.

Novel compound heterozygous variants in FANCI cause premature ovarian insufficiency.

Premature ovarian insufficiency (POI) is a common reproductive aging disorder due to a dramatic decline of ovarian function before 40 years of age. Accumulating evidence reveals that genetic defects, particularly those related to DNA damage response, are a crucial contributing factor to POI. We have demonstrated that the functional Fanconi anemia (FA) pathway maintains the rapid proliferation of primordial germ cells to establish a sufficient reproductive reserve by counteracting replication stress, but the clinical implications of this function in human ovarian function remain to be established. Here, we screened the FANCI gene, which encodes a key component for FA pathway activation, in our whole-exome sequencing database of 1030 patients with idiopathic POI, and identified two pairs of novel compound heterozygous variants, c.[97C > T];[1865C > T] and c.[158-2A > G];[c.959A > G], in two POI patients, respectively. The missense variants did not alter FANCI protein expression and nuclear localization, apart from the variant c.158-2A > G causing abnormal splicing and leading to a truncated mutant p.(S54Pfs*5). Furthermore, the four variants all diminished FANCD2 ubiquitination levels and increased DNA damage under replication stress, suggesting that the FANCI variants impaired FA pathway activation and replication stress response. This study first links replication stress response defects with the pathogenesis of human POI, providing a new insight into the essential roles of the FA genes in ovarian function.

UBE2T resolves transcription-replication conflicts and protects common fragile sites in primordial germ cells.

The proper development of primordial germ cells (PGCs) is an essential prerequisite for gametogenesis and mammalian fertility. The Fanconi anemia (FA) pathway functions in maintaining the development of PGCs. FANCT/UBE2T serves as an E2 ubiquitin-conjugating enzyme that ubiquitylates the FANCD2-FANCI complex to activate the FA pathway, but its role in the development of PGCs is not clear. In this study, we found that Ube2t knockout mice showed defects in PGC proliferation, leading to severe loss of germ cells after birth. Deletion of UBE2T exacerbated DNA damage and triggered the activation of the p53 pathway. We further demonstrated that UBE2T counteracted transcription-replication conflicts by resolving R-loops and stabilizing replication forks, and also protected common fragile sites by resolving R-loops in large genes and promoting mitotic DNA synthesis to maintain the genome stability of PGCs. Overall, these results provide new insights into the function and regulatory mechanisms of the FA pathway ensuring normal development of PGCs.

FAAP100 is required for the resolution of transcription-replication conflicts in primordial germ cells.

BACKGROUND: The maintenance of genome stability in primordial germ cells (PGCs) is crucial for the faithful transmission of genetic information and the establishment of reproductive reserve. Numerous studies in recent decades have linked the Fanconi anemia (FA) pathway with fertility, particularly PGC development. However, the role of FAAP100, an essential component of the FA core complex, in germ cell development is unexplored. RESULTS: We find that FAAP100 plays an essential role in R-loop resolution and replication fork protection to counteract transcription-replication conflicts (TRCs) during mouse PGC proliferation. FAAP100 deletion leads to FA pathway inactivation, increases TRCs as well as cotranscriptional R-loops, and contributes to the collapse of replication forks and the generation of DNA damage. Then, the activated p53 signaling pathway triggers PGC proliferation defects, ultimately resulting in insufficient establishment of reproductive reserve in both sexes of mice. CONCLUSIONS: Our findings suggest that FAAP100 is required for the resolution of TRCs in PGCs to safeguard their genome stability.

Homozygous missense variant in MEIOSIN causes premature ovarian insufficiency.

STUDY QUESTION: Are variants of genes involved in meiosis initiation responsible for premature ovarian insufficiency (POI)? SUMMARY ANSWER: A MEIOSIN variant participates in the pathogenesis of human POI by impairing meiosis due to insufficient transcriptional activation of essential meiotic genes. WHAT IS KNOWN ALREADY: Meiosis is the key event for the establishment of the ovarian reserve, and several gene defects impairing meiotic homologous recombination have been found to contribute to the pathogenesis of POI. Although STRA8 and MEIOISN variants have been found to associate with POI in a recent study, the condition of other meiosis initiation genes is unknown and direct evidence of variants participating in the pathogenesis of POI is still lacking. STUDY DESIGN, SIZE, DURATION: This was a retrospective genetic study. An in-house whole exome sequencing (WES) database of 1030 idiopathic POI patients was screened for variations of meiosis initiation genes. PARTICIPANTS/MATERIALS, SETTING, METHODS: Homozygous or compound heterozygous variations of genes involved in meiosis initiation were screened in the in-house WES database. The pathogenicity of the variation was verified by in vitro experiments, including protein structure prediction and dual-luciferase reporter assay. The effect of the variant on ovarian function and meiosis was demonstrated through histological analyses in a point mutation mouse model. MAIN RESULTS AND THE ROLE OF CHANCE: One homozygous variant in MEIOSIN (c.1735C>T, p.R579W) and one in STRA8 (c.258 + 1G>A), which initiates meiosis via the retinoic acid-dependent pathway, were identified in a patient with idiopathic POI respectively. The STRA8 variation has been reported in the recently published work. For the MEIOSIN variation, the dual-luciferase reporter assay revealed that the variant adversely affected the transcriptional function of MEIOSIN in upregulating meiotic genes. Furthermore, knock-in mice with the homologous mutation confirmed that the variation impacted the meiotic prophase I program and accelerated oocyte depletion. Moreover, the variant p.R579W localizing in the high-mobility group (HMG) box domain disrupted the nuclear localization of the MEIOSIN protein but was dispensable for the cell-cycle switch of oocytes, suggesting a unique role of the MEIOSIN HMG box domain in meiosis initiation. LIMITATIONS, REASONS FOR CAUTION: Further studies are needed to explore the role of other meiosis initiation genes in the pathogenesis of POI. WIDER IMPLICATIONS OF THE FINDINGS: The MEIOSIN variant was verified to cause POI by impaired transcriptional regulation of meiotic genes and was inherited by a recessive mode. The function of HMG box domain in MEIOSIN protein was also expanded by this study. Although causative variations in meiotic initiation genes are rare in POI, our study confirmed the pathogenicity of a MEIOSIN variant and elucidated another mechanism of human infertility. STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the National Key Research & Developmental Program of China (2022YFC2703800, 2022YFC2703000), National Natural Science Foundation for Distinguished Young Scholars (82125014), National Natural Science Foundation of China (32070847, 32170867, 82071609), Basic Science Center Program of NSFC (31988101), Natural Science Foundation of Shandong Province for Grand Basic Projects (ZR2021ZD33), Natural Science Foundation of Shandong Province for Excellent Young Scholars (ZR2022YQ69), Taishan Scholars Program for Young Experts of Shandong Province (tsqn202211371), and Qilu Young Scholars Program of Shandong University. The authors declare no conflict of interest. TRIAL REGISTRATION NUMBER: N/A.

Long noncoding RNA HCP5 participates in premature ovarian insufficiency by transcriptionally regulating MSH5 and DNA damage repair via YB1.

The genetic etiology of premature ovarian insufficiency (POI) has been well established to date, however, the role of long noncoding RNAs (lncRNAs) in POI is largely unknown. In this study, we identified a down-expressed lncRNA HCP5 in granulosa cells (GCs) from biochemical POI (bPOI) patients, which impaired DNA damage repair and promoted apoptosis of GCs. Mechanistically, we discovered that HCP5 stabilized the interaction between YB1 and its partner ILF2, which could mediate YB1 transferring into the nucleus of GCs. HCP5 silencing affected the localization of YB1 into nucleus and reduced the binding of YB1 to the promoter of MSH5 gene, thereby diminishing MSH5 expression. Taken together, we identified that the decreased expression of HCP5 in bPOI contributed to dysfunctional GCs by regulating MSH5 transcription and DNA damage repair via the interaction with YB1, providing a novel epigenetic mechanism for POI pathogenesis.

FANCL gene mutations in premature ovarian insufficiency.

The Fanconi anemia (FA) pathway is mainly involved in DNA interstrand crosslinks (ICLs) repair in the genome. Several FA genes, including FANCD1/BRCA2, FANCM, and FANCU/XRCC2, have been identified as causative genes for premature ovary insufficiency (POI). Fanconi anemia group L protein (FANCL) cooperates with FANCT/UBE2T to ubiquitinate the FANCI-D2 dimer, which is a crucial event in the process of ICLs repair. Fancl-knockout mice phenocopy human POI, but the role of FANCL mutations in POI pathogenesis has not been confirmed. In the present work, potentially pathogenic mutations in the FANCL gene were screened in 200 Chinese patients with idiopathic POI and in 200 matched controls. Two novel heterozygous frameshift mutations, c.1048_1051delGTCT (p.Gln350Valfs*18) and c.739dupA (p.Met247Asnfs*4), were identified in the FANCL gene in POI patients but not in controls. Wild-type FANCL protein was predominantly localized in the nuclei, while both mutant FANCL proteins were retained in the cytoplasm. In addition, the FANCL variants exhibited impaired ubiquitin-ligase activity and compromised DNA repair ability after mitomycin C treatment. Furthermore, the FANCL variants were deleterious and might be associated with haploinsufficiency. Our results show that FANCL mutations are potentially causative for POI by disrupting DNA damage repair processes.

MicroRNA-127-5p impairs function of granulosa cells via HMGB2 gene in premature ovarian insufficiency.

Distinct microRNA (miRNA) profiles have been reported in premature ovarian insufficiency (POI), but their functional relevance in POI is not yet clearly stated. In this study, aberrant expressions of miR-127-5p and high mobility group box 2 (HMGB2) were observed by microarrays in granulosa cells (GCs) from biochemical POI (bPOI) women and further confirmed by a quantitative reverse-transcription polymerase chain reaction. Immortalized human granulosa cell line and mouse primary ovarian GCs were used for functional validation. Orthotopic mouse model was established to examine the role of miR-127-5p in vivo. Finally, the expression of miR-127-5p was measured in the plasma of bPOI women. The receiver operating characteristic curve analysis was performed to determine the indicative role of miR-127-5p for ovarian reserve. Results showed the upregulation of miR-127-5p was identified in GCs from bPOI patients. It inhibited GCs proliferation and impaired DNA damage repair capacity through targeting HMGB2, which was significantly downregulated in GCs from the same cohort of cases. miR-127-5p was confirmed to attenuate DNA repair capability via HMGB2 in mouse ovary in vivo. Intriguingly, the upexpression of miR-127-5p was also detected in plasma of bPOI individuals, suggesting that miR-127-5p could be a promising indicator for bPOI. Taken together, our results discovered the deleterious effects of miR-127-5p on GCs function and its predictive value in POI process. The target gene HMGB2 could be considered as a new candidate for POI. This study highlights the importance of DNA repair capacity for ovarian function and sheds light on the epigenetic mechanism in the pathogenicity of POI.

Variation analysis of tousled like kinase 1 gene in patients with sporadic premature ovarian insufficiency.

Tousled like kinase 1 (TLK1), a member of DNA repair family, participates in the regulation of chromatin assembly and is associated with early menopause and premature ovarian insufficiency (POI) in European women. However, whether the sequence variant in the TLK1 gene was causative for POI is still elusive. Here we performed direct sequencing of the TLK1 gene in 192 patients with sporadic POI. All exons and exon-intron boundaries of TLK1 were amplified and sequenced. Six known single-nucleotide polymorphisms were identified in POI, including rs149844334, rs11553951, rs757600673, rs2277339, rs113416007 and rs17283147. No novel variant was identified, which indicates that sequence variants in the coding region of TLK1 might be uncommon in Chinese women with POI. The role of TLK1 in POI pathogenesis needs to be further explored in larger cohorts from Chinese and other ethnic populations.

Variation analysis of SOX8 gene in Chinese men with non-obstructive azoospermia or oligozoospermia.

Sox8, encoding a SRY-related HMG box transcription factor, is essential in Sertoli cells for germ cell differentiation via regulation of integrity of the blood-testis barrier (BTB) as well as Sertoli-germ cell adhesion. Inactivation of Sox8 gene in mice causes postnatal progressive spermatogenic failure, resulting in male infertility. This study aims to investigate whether variants of SOX8 contribute to pathogenesis of idiopathic non-obstructive azoospermia (NOA) or oligozoospermia. A case-control genetic study was conducted in which all exons and exon-intron boundaries of SOX8 gene were screened in 190 NOA and 139 oligozoospermia cases by Sanger sequencing. The detected variants were examined in 284 normospermic controls. Nine known single-nucleotide polymorphisms (SNPs) of SOX8 gene were identified, and four of them exist simultaneously in oligo/azoospermia patients. A comparison of allele/genotype frequencies of these variants showed no significant difference between oligo/azoospermia cases and controls. The results indicate that deleterious variants in SOX8 gene may not be a common cause for oligo/azoospermia in Chinese men. Considering ethnic diversity, SOX8 could not be ruled out as a candidate gene for male infertility. The role of SOX8-mediated Sertoli cell function and BTB integrity played in the pathogenesis of male infertility needs to be further explored in other populations.

A novel FOXL2 mutation in two infertile patients with blepharophimosis-ptosis-epicanthus inversus syndrome.

BACKGROUND: Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is a rare, autosomal dominant disease. There are two clinical types of BPES: type I patients have eyelid abnormalities accompanied by infertility in affected females, while type II patients only display eyelid malformations. Previous studies have reported that the forkhead box L2 (FOXL2) gene mutations cause BPES. PURPOSE: To identify plausible FOXL2 mutation in a Chinese family with BPES and infertility METHODS: Mutational screening of FOXL2 was performed in the affected members and 223 controls. Functional characterization of the novel mutation identified was carried out in vitro by luciferase reporter assay and subcellular localization experiment. RESULTS: A novel heterozygous mutation c.188 T > A (p.I63N) in FOXL2 was identified in two BPES patients in this family. The mutation abolished the transcriptional repression of FOXL2 on the promoters of CYP19A1 and CCND2 genes, as shown by luciferase reporter assays. However, no dominant-negative effect was observed for the mutation, and it did not impact FOXL2 protein nuclear localization and distribution. CONCLUSIONS: The mutation c.188 T > A (p.I63N) in FOXL2 might be causative for BPES and infertility in this family and further amplified the spectrum of FOXL2 mutations.

Mutations in MSH5 in primary ovarian insufficiency.

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.

Variation analysis of theTMEM150B gene in Chinese women with premature ovarian insufficiency.

RESEARCH QUESTION: The TMEM150B gene, which promotes cell survival under stress conditions by modulating autophagy, is closely associated with age at natural menopause, early menopause and premature ovarian insufficiency (POI) in European women. However, whether gene variants of TMEM150B contribute to the pathogenesis of POI needs to be determined. DESIGN: A case-control genetic study in 408 Han Chinese women with non-syndromic POI, in which all exons and exon-intron boundaries of the TMEM150B gene were screened by Sanger sequencing; the results were analysed by statistics and bioinformatics. RESULTS: Two novel variants located in the 3' untranslated region of the TMEM150B gene were identified, but bioinformation analyses showed that neither was potentially disease-causing. Six known single-nucleotide polymorphisms (SNP) were found, and they were not potentially causative for POI. The intronic SNP rs11668344 was also detected in the POI patients; no significant differences were found in either genotype or allele frequencies compared with the control population. CONCLUSION: The results suggest that the perturbations in the TMEM150B gene are not a common explanation for POI in Chinese women. The role of autophagy in the pathogenic mechanism of POI needs further exploration.

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.

Analysis of CDK2 mutations in Chinese men with non-obstructive azoospermia who underwent testis biopsy.

To examine whether mutations of the CDK2 gene exist in Chinese men with non-obstructive azoospermia (NOA) with different histopathology, we recruited 175 Chinese men with idiopathic NOA who underwent testis biopsy, including hypospermatogenesis, germ cell maturation arrest and Sertoli cell only syndrome. Genomic DNA was extracted from peripheral blood samples. Subsequently, the seven exons of the CDK2 gene were amplified using polymerase chain reaction with specific primers, respectively. The polymerase chain reaction products were sequenced on an automated sequencer. We identified four known single nucleotide polymorphisms: c.324G>A in exon 1; c.363T>C in exon 2; c.*570G>A; and c.*1160G>C in the 3' UTR of the CDK2 gene. Comparison of the genotype and allele frequencies showed no significant differences between NOA cases and controls for the four single nucleotide polymorphisms. Furthermore, no significant differences were found between each pathological group and control group, respectively. The results indicate that mutations in the coding sequence of the CDK2 gene may not be responsible for idiopathic NOA in Chinese men. Future studies in large cohorts of different ethnic populations are warranted to establish whether associations exist between the CDK2 gene and NOA.

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.

Variation analysis of PUM1 gene in Chinese women with primary ovarian insufficiency.

Accumulating evidence has indicated that the genes involved in meiosis are highly correlated with ovarian function. Pumilio 1 (PUM1) is a RNA-binding protein which is involved in the meiotic process. It has been reported that the Pum1 knockout female mice displayed subfertility due to the decrease in primordial follicle pool. The aim of our study is to investigate whether variants of the PUM1 gene are responsible for primary ovarian insufficiency (POI) in Chinese women. We analyzed coding sequence and untranslated regions of the PUM1 gene in 196 Han Chinese women with non-syndromic POI and 192 controls. Seven novel variants were identified, but one of them was synonymous and six were intronic. Besides, seven known single-nucleotide polymorphisms (SNPs) were found, and there were no significant differences in genotype and allele frequencies of the SNPs between patients and controls. The results suggest that the variants in PUM1 may not contribute to POI in Han Chinese women.

Variation analysis of PRIM1 gene in Chinese patients with primary ovarian insufficiency.

Insights into common genetic susceptibility between primary ovarian insufficiency (POI) and natural or early menopause have delivered an innovative way of assessing the genetic mechanisms involved in POI. PRIM1 plays a crucial role in DNA replication by synthesizing RNA primers for Okazaki fragments. It is closely associated with age at natural menopause, early menopause and POI in European women. In this study, we aimed to investigate whether mutations in PRIM1 contribute to POI in Chinese women. All exons and exon-intron boundaries of PRIM1 gene were sequenced in 192 Han Chinese women with non-syndromic POI. No plausible mutations were identified. The results suggest that the perturbations in PRIM1 gene are not a common explanation for POI in Chinese women.