Meiotic Recombination Defects and Premature Ovarian Insufficiency

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.

The crosstalk between telomeres and DNA repair mechanisms: an overview to mammalian somatic cells, germ cells, and preimplantation embryos

Telomeres are located at the ends of linear chromosomes and play a critical role in maintaining genomic stability by preventing premature activation of DNA repair mechanisms. Because of exposure to various genotoxic agents, telomeres can undergo shortening and genetic changes. In mammalian cells, the basic DNA repair mechanisms, including base excision repair, nucleotide excision repair, double-strand break repair, and mismatch repair, function in repairing potential damages in telomeres. If these damages are not repaired correctly in time, the unfavorable results such as apoptosis, cell cycle arrest, and cancerous transition may occur. During lifespan, mammalian somatic cells, male and female germ cells, and preimplantation embryos experience a number of telomeric damages. Herein, we comprehensively reviewed the crosstalk between telomeres and the DNA repair mechanisms in the somatic cells, germ cells, and embryos. Infertility development resulting from possible defects in this crosstalk is also discussed in the light of existing studies.

Improving diagnostic precision in primary ovarian insufficiency using comprehensive genetic and autoantibody testing

STUDY QUESTION

Is it possible to find the cause of primary ovarian insufficiency (POI) in more women by extensive screening?

SUMMARY ANSWER

Adding next generation sequencing techniques including a POI-associated gene panel, extended whole exome sequencing data, as well as specific autoantibody assays to the recommended diagnostic investigations increased the determination of a potential etiological diagnosis of POI from 11% to 41%.

WHAT IS KNOWN ALREADY

POI affects ∼1% of women. Clinical presentations and pathogenic mechanisms are heterogeneous and include genetic, autoimmune, and environmental factors, but the underlying etiology remains unknown in the majority of cases.

STUDY DESIGN, SIZE, DURATION

Prospective cross-sectional study of 100 women with newly diagnosed POI of unknown cause consecutively referred to Haukeland University Hospital, Bergen, Norway, January 2019 to December 2021.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In addition to standard recommended diagnostic investigations including screening for chromosomal anomalies and premutations in the fragile X mental retardation 1 gene (FMR1) we used whole exome sequencing, including targeted analysis of 103 ovarian-related genes, and assays of autoantibodies against steroid cell antigens.

MAIN RESULTS AND THE ROLE OF CHANCE

We identified chromosomal aberrations in 8%, FMR1 premutations in 3%, genetic variants related to POI in 16%, and autoimmune POI in 3%. Furthermore in 11% we identified POI associated genetic Variants of unknown signifcance (VUS). A homozygous pathogenic variant in the ZSWIM7 gene (NM_001042697.2) was found in two women, corroborating this as a novel cause of monogenic POI. No associations between phenotypes and genotypes were found.

LIMITATIONS, REASONS FOR CAUTION

Use of candidate genetic and autoimmune markers limit the possibility to discover new markers. To further investigate the genetic variants, family studies would have been useful. We found a relatively high proportion of genetic variants in women from Africa and lack of genetic diversity in the genomic databases can impact diagnostic accuracy.

WIDER IMPLICATIONS OF THE FINDINGS

Since no specific clinical or biochemical markers predicted the underlying cause of POI discussion of which tests should be part of diagnostic screening in clinical practice remains open. New technology has altered the availability and effectiveness of genetic testing, and cost-effectiveness analyses are required to aid sustainable diagnostics.

STUDY FUNDING/COMPETING INTEREST(S)

The study was supported by grants and fellowships from Stiftelsen Kristian Gerhard Jebsen, the Novonordisk Foundation, the Norwegian Research Council, University of Bergen, and the Regional Health Authorities of Western Norway. The authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

NCT04082169.

BCAS2 regulates oocyte meiotic prophase I by participating in mRNA alternative splicing

Oocyte meiotic prophase I (MI) is an important event in female reproduction. Breast cancer amplified sequence 2 (BCAS2) is a component of the spliceosome. Previous reports have shown that BCAS2 is critical in male germ cell meiosis, oocyte development, and early embryo genome integrity. However, the role of BCAS2 in oocyte meiosis has not been reported. We used Stra8-GFPCre mice to knock out Bcas2 in oocytes during the pachytene phase. The results of fertility tests showed that Bcas2 conditional knockout (cKO) in oocytes results in infertility in female mice. Morphological analysis showed that the number of primordial follicles in the ovaries of 2-month-old (M) mice was significantly reduced and that follicle development was blocked. Further analysis showed that the number of primordial follicles decreased and that follicle development was slowed in 7-day postpartum (dpp) ovaries. Moreover, primordial follicles undergo apoptosis, and DNA damage cannot be repaired in primary follicle oocytes. Meiosis was abnormal; some oocytes could not reach the diplotene stage, and more oocytes could not develop to the dictyotene stage. Alternative splicing (AS) analysis revealed abnormal AS of deleted in azoospermia like (Dazl) and diaphanous related formin 2 (Diaph2) oogenesis-related genes in cKO mouse ovaries, and the process of AS was involved by CDC5L and PRP19.

Emerging trends and research priorities in premature ovarian insufficiency genes: a bibliometric and visualization study

PURPOSE

To illustrate the results achieved by genes in premature ovarian insufficiency (POI) and collaborations in the field, and to explore key themes and future directions.

METHODS

Articles and reviews related to POI genes published between 1990 and 2022 were retrieved from the Web of Science core collection (WoSCC) for the total bibliometric analysis. Tools were analyzed for publication, country, institution, journal, authors, reference, keywords, subject categories, funding agencies, and research hotspots using a bibliometric online analysis platform, Bibliographic Co-occurrence Matrix Builder (BICOMB), CiteSpace V, and VOSviewer.

RESULTS

A total of 2,232 papers were included in this study. Articles were published in 52 countries, with the United States publishing the most, followed by China. A total of 308 institutions contributed to relevant publications. Shandong University published the most papers. Qin Y's team published the most relevant papers. Human reproduction and fertility and sterility are the two journals with the most papers. X-chromosome abnormalities, transcription factor mutations, and FMR1 genes are the directions of more POI, and DNA repair is the keyword of the research frontier in recent years.

CONCLUSIONS

This study summarizes the relevant literature on POI gene research for the first time and analyzes the current hotspots and future trends in this field. The findings can further reveal the etiology, diagnosis, and treatment of POI, which is beneficial for researchers to grasp the genetic dynamics of POI women.

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.

Research progress of the Fanconi anemia pathway and premature ovarian insufficiency†

The Fanconi anemia pathway is a key pathway involved in the repair of deoxyribonucleic acidinterstrand crosslinking damage, which chiefly includes the following four modules: lesion recognition, Fanconi anemia core complex recruitment, FANCD2-FANCI complex monoubiquitination, and downstream events (nucleolytic incision, translesion synthesis, and homologous recombination). Mutations or deletions of multiple Fanconi anemia genes in this pathway can damage the interstrand crosslinking repair pathway and disrupt primordial germ cell development and oocyte meiosis, thereby leading to abnormal follicular development. Premature ovarian insufficiency is a gynecological clinical syndrome characterized by amenorrhea and decreased fertility due to decreased oocyte pool, accelerated follicle atresia, and loss of ovarian function in women <40 years old. Furthermore, in recent years, several studies have detected mutations in the Fanconi anemia gene in patients with premature ovarian insufficiency. In addition, some patients with Fanconi anemia exhibit symptoms of premature ovarian insufficiency and infertility. The Fanconi anemia pathway and premature ovarian insufficiency are closely associated.

Pathogenic bi-allelic variants of meiotic ZMM complex gene SPO16 in premature ovarian insufficiency

Premature ovarian insufficiency (POI) is a heterogeneous disease affecting the physical and mental health of millions of women worldwide. The contribution of genetic factors in the pathogenesis of POI has increased, with quite a few of causative genes involved in meiosis. ZMM proteins are a group of conserved proteins participating in meiotic synapsis and crossover maturation. Here, by screening the variations of ZMM genes in our in-house WES database of 1030 idiopathic POI patients, one novel homozygous variation in SPO16 (c.160 + 8A > G) was firstly identified in one patient. The variation was verified to disturb mRNA splicing by minigene assay, produced a non-functional SPO16 protein, and was classified as pathogenetic according to American College of Medical Genetics guideline. During meiotic prophase I, SHOC1 binds to branched DNA and recruits SPO16 and other ZMM proteins to facilitate crossover formation. Together with our recent identified bi-allelic variations of SHOC1 in a published work, this study highlighted the essential roles of ZMM genes in the maintenance of ovarian function and expanded the POI gene spectrum.

Loss of function of FIGNL1, a DNA damage response gene, causes human ovarian dysgenesis

Ovarian dysgenesis (OD), an XX disorder of sex development, presents with primary amenorrhea, hypergonadotrophic hypogonadism, and infertility. In an Ashkenazi Jewish patient with OD, whole exome sequencing identified compound heterozygous frameshifts in FIGNL1, a DNA damage response (DDR) gene: c.189del and c.1519_1523del. Chromosomal breakage was significantly increased in patient cells, both spontaneously, and following mitomycin C exposure. Transfection of DYK-tagged FIGNL1 constructs in HEK293 cells showed no detectable protein in FIGNL1c.189del and truncation with reduced expression in FIGNL1c.1519_1523del (64% of wild-type [WT], P = .003). FIGNL1 forms nuclear foci increased by phleomycin treatment (20.6 ± 1.6 vs 14.8 ± 2.4, P = .02). However, mutant constructs showed reduced DYK-FIGNL1 foci formation in non-treated cells (0.8 ± 0.9 and 5.6 ± 1.5 vs 14.8 ± 2.4 in DYK-FIGNL1WT, P < .001) and no increase with phleomycin treatment. In conclusion, FIGNL1 loss of function is a newly characterized OD gene, highlighting the DDR pathway's role in ovarian development and maintenance and suggesting chromosomal breakage as an assessment tool in XX-DSD patients.

Fance deficiency inhibits primordial germ cell proliferation associated with transcription-replication conflicts accumulate and DNA repair defects

Fanconi anemia (FA) gene mutations are critical components in the genetic etiology of premature ovarian insufficiency (POI). Fance-/- mice detected meiotic arrest of primordial germ cells (PGCs) as early as embryonic day (E) 13.5 and exhibited decreased ovarian reserve after birth. However, the mechanism of Fance defect leading to dysgenesis of PGCs is unclear. We aimed to explore the effect of Fance defects on mitotic proliferation of PGCs. Combined with transcriptomic sequencing and validation, we examined the effect of Fance defects on cell cycle, transcription-replication conflicts (TRCs), and multiple DNA repair pathways in PGCs during active DNA replication at E11.5 and E12.5. Results showed Fance defects cause decreased numbers of PGCs during rapid mitosis at E11.5 and E12.5. Mitotic cell cycle progression of Fance-/- PGCs was blocked at E11.5 and E12.5, shown by decreased cell proportions in S and G2 phases and increased cell proportions in M phase. RNA-seq suggested the mechanisms involved in DNA replication and repair. We found Fance-/- PGCs accumulate TRCs during active DNA replication at E11.5 and E12.5. Fance-/- PGCs down-regulate multiple DNA repair pathways at E11.5 and E12.5 including the FA pathway, homologous recombination (HR) pathway, and base excision repair (BER) pathway. In conclusion, Fance defect impaired the mitotic proliferation of PGCs leading to rapidly decreased numbers and abnormal cell cycle distribution. Proliferation inhibition of Fance-/- PGCs was associated with accumulated TRCs and down-regulation of FA, HR, BER pathways. These provided a theoretical basis for identifying the inherited etiology and guiding potential fertility management for POI.

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.

SRSF1 regulates primordial follicle formation and number determination during meiotic prophase I

BACKGROUND

Ovarian folliculogenesis is a tightly regulated process leading to the formation of functional oocytes and involving successive quality control mechanisms that monitor chromosomal DNA integrity and meiotic recombination. A number of factors and mechanisms have been suggested to be involved in folliculogenesis and associated with premature ovarian insufficiency, including abnormal alternative splicing (AS) of pre-mRNAs. Serine/arginine-rich splicing factor 1 (SRSF1; previously SF2/ASF) is a pivotal posttranscriptional regulator of gene expression in various biological processes. However, the physiological roles and mechanism of SRSF1 action in mouse early-stage oocytes remain elusive. Here, we show that SRSF1 is essential for primordial follicle formation and number determination during meiotic prophase I.

RESULTS

The conditional knockout (cKO) of Srsf1 in mouse oocytes impairs primordial follicle formation and leads to primary ovarian insufficiency (POI). Oocyte-specific genes that regulate primordial follicle formation (e.g., Lhx8, Nobox, Sohlh1, Sohlh2, Figla, Kit, Jag1, and Rac1) are suppressed in newborn Stra8-GFPCre Srsf1^Fl/Fl mouse ovaries. However, meiotic defects are the leading cause of abnormal primordial follicle formation. Immunofluorescence analyses suggest that failed synapsis and an inability to undergo recombination result in fewer homologous DNA crossovers (COs) in the Srsf1 cKO mouse ovaries. Moreover, SRSF1 directly binds and regulates the expression of the POI-related genes Six6os1 and Msh5 via AS to implement the meiotic prophase I program.

CONCLUSIONS

Altogether, our data reveal the critical role of an SRSF1-mediated posttranscriptional regulatory mechanism in the mouse oocyte meiotic prophase I program, providing a framework to elucidate the molecular mechanisms of the posttranscriptional network underlying primordial follicle formation.

Management of a Girl With Delayed Puberty and Elevated Gonadotropins

A girl presenting with delayed puberty and elevated gonadotropins may have a range of conditions such as Turner syndrome (TS), primary ovarian insufficiency (POI), and 46,XY disorders of sexual development (DSD). An organized and measured approach to investigation can help reach a timely diagnosis. Management of young people often requires specialist multidisciplinary input to address the endocrine and nonendocrine features of these complex conditions, as well as the psychological challenges posed by their diagnosis. Next-generation sequencing within the research setting has revealed several genetic causes of POI and 46,XY DSD, which may further facilitate an individualized approach to care of these young people in the future. Pubertal induction is required in many and the timing of this may need to be balanced with other issues specific to the condition (eg, allowing time for information-sharing in 46,XY DSD, optimizing growth in TS). Shared decision-making and sign-posting to relevant support groups from the outset can help empower young people and their families to manage these conditions. We describe 3 clinical vignettes of girls presenting with delayed puberty and hypergonadotropic amenorrhea and discuss their clinical management in the context of current literature and guidelines.

Mouse oocytes carrying metacentric Robertsonian chromosomes have fewer crossover sites and higher aneuploidy rates than oocytes carrying acrocentric chromosomes alone

Meiotic homologous recombination during fetal development dictates proper chromosome segregation in adult mammalian oocytes. Successful homologous synapsis and recombination during Meiotic Prophase I (MPI) depends on telomere-led chromosome movement along the nuclear envelope. In mice, all chromosomes are acrocentric, while other mammalian species carry a mixture of acrocentric and metacentric chromosomes. Such differences in telomeric structures may explain the exceptionally low aneuploidy rates in mice. Here, we tested whether the presence of metacentric chromosomes carrying Robertsonian translocations (RbT) affects the rate of homologous recombination or aneuploidy. We found a delay in MPI progression in RbT-carrier vs. wild-type (WT) fetal ovaries. Furthermore, resolution of distal telomere clusters, associated with synapsis initiation, was delayed and centromeric telomere clusters persisted until later MPI substages in RbT-carrier oocytes compared to WT oocytes. When chromosomes fully synapsed, higher percentages of RbT-carrier oocytes harbored at least one chromosome pair lacking MLH1 foci, which indicate crossover sites, compared to WT oocytes. Aneuploidy rates in ovulated eggs were also higher in RbT-carrier females than in WT females. In conclusion, the presence of metacentric chromosomes among acrocentric chromosomes in mouse oocytes delays MPI progression and reduces the efficiency of homologous crossover, resulting in a higher frequency of aneuploidy.

MEIOK21 regulates oocyte quantity and quality via modulating meiotic recombination

The reproductive life span of females is largely determined by the number and quality of oocytes. Previously, we identified MEIOK21 as a meiotic recombination regulator required for male fertility. Here, we characterize the important roles of MEIOK21 in regulating female meiosis and oocyte number and quality. MEIOK21 localizes at recombination sites as a component of recombination bridges in oogenesis like in spermatogenesis. Meiok21^-/- female mice show subfertility. Consistently, the size of the primordial follicle pool in Meiok21^-/- females is only ~40% of wild-type females because a great number of oocytes with defects in meiotic recombination and/or synapsis are eliminated. Furthermore, the numbers of primordial and growing follicles show a more marked decrease in an age-dependent manner compared with wild-type females. Further analysis shows Meiok21^-/- oocytes also have reduced rates of germinal vesicle breakdown and the first polar body extrusion when cultured in vitro, indicating poor oocyte quality. Additionally, Meiok21^-/- oocytes have more chromosomes bearing a single distally localized crossover (chiasmata), suggesting a possible defect in crossover maturation. Taken together, our findings indicate critical roles for MEIOK21 in ensuring the number and quality of oocytes in the follicles.

Fancb deficiency causes premature ovarian insufficiency in mice†

FANCB protein is a major component of the Fanconi anemia (FA) core complex and plays important role in hematopoiesis and germ cell development. Deletion of Fancb gene causes the defect of primordial germ cells (PGCs) development and infertility in male mice. However, it remains unknown whether Fancb is required for female germ cell development. In this study, we found that the fertility of Fancb knockout male mice in C57/ICR mixed backgrounds was not affected. Female Fancb-/- mice were obtained by crossing Fancb+/- females with Fancb-/Y males. The number of PGCs was dramatically decreased in Fancb-/- females. Very few oocytes were observed after birth and primordial follicle pool was completely depleted at 6 weeks of age in Fancb-/- females. However, the remained oocytes from Fancb-/- mice were normal in fertilization and embryonic development from 2-cell to blastocyst stage. We also found that Fancb and Fancl double knockout males were also fertile and the number of sperm in epididymis was not reduced comparable to that of Fancb-/- and Fancl-/- single knockout mice. Taken together, these results demonstrated that Fancb is also essential for female germ cell development. Inactivation of Fancb causes massive germ cell loss and infertility in adult females. We also found that Fancb and Fancl do not act synergistically in regulating germ cell development.

Prdm9 deficiency of rat oocytes causes synapsis among non-homologous chromosomes and aneuploidy

Aneuploidy (abnormal chromosome number) accompanies reduced ovarian function in humans and mice, but the reasons behind this concomitance remain underexplored. Some variants in the human gene encoding histone-3-lysine-4,36-trimethyltransferase PRDM9 are associated with aneuploidy, and other variants with ovarian function reduced by premature ovarian failure (POF), but no link between POF and aneuploidy has been revealed. SHR/OlaIpcv rat females lacking PRDM9 manifest POF-a reduced follicle number, litter size, and reproductive age. Here, we explored this model to test how POF relates to oocyte euploidy. The mutant rat females displayed increased oocyte aneuploidy and embryonic death of their offspring compared to controls. Because rat PRDM9 positions meiotic DNA breaks, we investigated the repair of these breaks. Fertile control rodents carry pachytene oocytes with synapsed homologous chromosomes and repaired breaks, while sterile Prdm9-deficient mice carry pachytene-like oocytes with many persisting breaks and asynapsed chromosomes. However, most PRDM9-lacking rat oocytes displayed a few persisting breaks and non-homologous synapsis (NHS). HORMAD2 protein serves as a barrier to sister-chromatid repair and a signal for the synapsis and DNA repair checkpoints. NHS but not asynapsis was associated with HORMAD2 levels similar to the levels on rat pachytene chromosomes with homologous synapsis. NHS was accompanied by crossing-over decreased below the minimum that is essential for euploidy. We argue that the increased mutant rat aneuploidy is due to NHS, which allows some oocytes to pass meiotic checkpoints without one crossing-over per chromosomal pair, leading to segregation errors, and thereby NHS links POF to aneuploidy.

Pathogenic Variants in ZSWIM7 Cause Primary Ovarian Insufficiency

CONTEXT

Primary ovarian insufficiency (POI) is a genetically heterogeneous condition associated with infertility and an increased risk of comorbidities. An increased number of genes implicated in DNA damage response pathways has been associated with POI as well as predisposition to cancers.

OBJECTIVE

We sought to identify and characterize patients affected by POI caused by pathogenic variants in genes involved in DNA damage response during meiosis.

SETTING

Study subjects were recruited at academic centers.

PATIENTS OR OTHER PARTICIPANTS

Individuals with a diagnosis of POI and their family members were enrolled for genetic analysis. Clinical findings, family history, and peripheral blood samples were collected.

RESEARCH DESIGN

Exome sequencing was performed on the study participants and their family members (when available). Protein conservation analysis and in silico modeling were used to obtain the structural model of the detected variants in the ZSWIM7 gene.

MAIN OUTCOME MEASURE(S)

Rare deleterious variants in known and candidate genes associated with POI.

RESULTS

Homozygous deleterious variants in the ZSWIM7 gene were identified in 2 unrelated patients with amenorrhea, an absence of puberty, and prepubertal ovaries and uterus. Observed variants were shown to alter the ZSWIM7 DNA-binding region, possibly affecting its function.

CONCLUSIONS

Our study highlights the pivotal role of the ZSWIM7 gene involved in DNA damage response during meiosis on ovarian development and function. Characterization of patients with defects in DNA repair genes has important diagnostic and prognostic consequences for clinical management and reproductive decisions.

Loss of atm in Zebrafish as a Model of Ataxia–Telangiectasia Syndrome

Ataxia–telangiectasia mutated (ATM) is a key DNA damage signaling kinase that is mutated in humans with ataxia–telangiectasia (A-T) syndrome. This syndrome is characterized by neurodegeneration, immune abnormality, cancer predisposition, and premature aging. To better understand the function of ATM in vivo, we engineered a viable zebrafish model with a mutated atm gene. Zebrafish atm loss-of-function mutants show characteristic features of A-T-like motor disturbance, including coordination disorders, immunodeficiency, and tumorigenesis. The immunological disorder of atm homozygote fish is linked to the developmental blockade of hematopoiesis, which occurs at the adulthood stage and results in a decrease in infection defense but, with little effect on wound healing. Malignant neoplasms found in atm mutant fish were mainly nerve sheath tumors and myeloid leukemia, which rarely occur in A-T patients or Atm−/− mice. These results underscore the importance of atm during immune cell development. This zebrafish A-T model opens up a pathway to an improved understanding of the molecular basis of tumorigenesis in A-T and the cellular role of atm.

Premature ovarian insufficiency

The natural lifespan of the ovary is occasionally interrupted by pathological processes; some are known, but many are unknown. Premature ovarian insufficiency (POI) can be a devastating diagnosis for an adolescent or for someone who has yet to start a family. Common causes of POI include genetic and chromosomal defects, autoimmune damage, and cancer treatments. Knowledge of the pathogenesis of this condition and an awareness of contemporary hormone replacement and fertility options are required to design a multidisciplinary therapeutic approach comprising reproductive medicine, endocrinology, clinical psychology, and assisted fertility expertise.

Mesenchymal Stem Cells in Premature Ovarian Insufficiency: Mechanisms and Prospects

Premature ovarian insufficiency (POI) is a complex endocrine disease that severely affects the physiological and reproductive functions of females. The current conventional clinical treatment methods for POI are characterized by several side effects, and most do not effectively restore the physiological functions of the ovaries. Transplantation of mesenchymal stem cells (MSCs) is a promising regenerative medicine approach, which has received significant attention in the management of POI with high efficacy. Associated pre-clinical and clinical trials are also proceeding orderly. However, the therapeutic mechanisms underlying the MSCs-based treatment are complex and have not been fully elucidated. In brief, proliferation, apoptosis, immunization, autophagy, oxidative stress, and fibrosis of ovarian cells are modulated through paracrine effects after migration of MSCs to the injured ovary. This review summarizes therapeutic mechanisms of MSCs-based treatments in POI and explores their therapeutic potential in clinical practice. Therefore, this review will provide a theoretical basis for further research and clinical application of MSCs in POI.

Human Umbilical Cord Mesenchymal Stem Cell-Derived Exosomes Improve Ovarian Function and Proliferation of Premature Ovarian Insufficiency by Regulating the Hippo Signaling Pathway

BACKGROUND

Premature ovarian insufficiency (POI) is associated with severe physical damage and psychological burden on women. Transplantation of exosomes is an encouraging regenerative medicine method, which has the potential for restoring ovarian functions on POI with high efficiency. This study aims at evaluating the therapeutic efficacy of human umbilical cord mesenchymal stem cell-derived exosomes (hUCMSC-Exos) on ovarian dysfunction of POI and the role of Hippo pathway in this exosome-mediated treatment.

METHODS

POI mice models were established through intraperitoneal injection of cyclophosphamide. Subsequently, transplantation of hUCMSC-Exos was conducted to administer POI mice. Ovaries and plasma of these mice models were harvested after two weeks of treatment. Ovarian morphology and follicle number were assessed by hematoxylin and eosin staining. Moreover, ELISA was used to detect hormone levels, which are related to ovarian function in serum. To assess the recovery of reproductive ability, we recorded the rate of pregnancy, the amount of offspring, and the time of birth in different groups. To explore the underlying mechanisms of exosome-mediated treatment for ovarian function recovery, the proliferation of ovarian cells in vivo was detected by immunohistochemistry and immunofluorescence staining. Additionally, we conducted EdU and CCK-8 assays to assess the proliferative ability of ovarian granulosa cells (GCs) that were cultured in vitro. Western blot analysis was conducted to estimate the proteins levels of Hippo- and proliferation-associated molecules in vivo and in vitro.

RESULTS

After transplantation of hUCMSC-Exos, the ovarian function-related hormone levels and the number of ovarian follicles returned to nearly normal degrees. Meanwhile, there was a significant improvement in reproductive outcomes after exosomal treatment. Furthermore, the improvement of ovarian function and proliferation was associated with the regulation of Hippo pathway. In vitro, co-culture with exosomes significantly elevated the proliferation of ovarian GCs by regulating Hippo pathway. However, the positive effects on the proliferation of GCs were significantly depressed when key Hippo pathway molecule was inhibited.

CONCLUSION

This study suggested that hUCMSC-Exos promoted ovarian functions and proliferation by regulating the Hippo pathway. Therefore, exosomal transplantation could be a promising and efficient clinical therapy for POI in the near future.