Synaptonemal Complex in Human Biology and Disease

The synaptonemal complex (SC) is a meiosis-specific multiprotein complex that forms between homologous chromosomes during prophase of meiosis I. Upon assembly, the SC mediates the synapses of the homologous chromosomes, leading to the formation of bivalents, and physically supports the formation of programmed double-strand breaks (DSBs) and their subsequent repair and maturation into crossovers (COs), which are essential for genome haploidization. Defects in the assembly of the SC or in the function of the associated meiotic recombination machinery can lead to meiotic arrest and human infertility. The majority of proteins and complexes involved in these processes are exclusively expressed during meiosis or harbor meiosis-specific subunits, although some have dual functions in somatic DNA repair and meiosis. Consistent with their functions, aberrant expression and malfunctioning of these genes have been associated with cancer development. In this review, we focus on the significance of the SC and their meiotic-associated proteins in human fertility, as well as how human genetic variants encoding for these proteins affect the meiotic process and contribute to infertility and cancer development.

A minimal genome design to maximally guarantee fertile inter-subspecific hybrid rice

Hybrid rice has made considerable contributions to achieve the ambitious goal of food security for the world's population. Hybrid rice from indica/xian and japonica/geng subspecies shows much higher heterosis and is thereby an important innovation in promoting rice production in the next decade. However, such inter-subspecific hybrid rice has long suffered from serious hybrid sterility, which is a major challenge that needs to be addressed. In this study, we performed a genome design strategy to produce fertile inter-subspecific hybrid by creation of wide compatibility varieties that are able to overcome hybrid sterility. Based on combined genetic analyses in two indica-japonica crosses, we determined that four hybrid sterility loci, S5, f5, pf12 and Sc, are the major QTLs controlling inter-subspecific hybrid sterility and thus the minimal targets that can be manipulated for breeding sub-specific hybrid rice. We then cloned the pf12 locus, one of the most effective loci for hybrid male sterility, by map-based cloning, and showed that artificial disruption of pf12A gene at this locus could successfully rescue hybrid fertility. We further dissected the genetic basis of wide compatibility using three pairwise crosses from a wide-compatibility variety Dular and representative indica and japonica varieties. On this basis, we constructed and assembled different combinations of naturally compatible alleles of four loci, S5, Sc, pf12, and f5, and found that the improved lines could fully recover pollen and embryo sac fertility in test-crossed F₁s, thereby completely fulfilling the demands of inter-subspecific hybrid spikelet fertility in agricultural production. This breeding scheme would facilitate redesign of future inter-subspecific hybrid rice with a higher yield potential.

Effects of adverse fertility-related factors on mitochondrial DNA in the oocyte: a comprehensive review

The decline of oocyte quality has profound impacts on fertilization, implantation, embryonic development, and the genetic quality of future generations. One factor that is often ignored but is involved in the decline of oocyte quality is mitochondrial DNA (mtDNA) abnormalities. Abnormalities in mtDNA affect the energy production of mitochondria, the dynamic balance of the mitochondrial network, and the pathogenesis of mtDNA diseases in offspring. In this review, we have detailed the characteristics of mtDNA in oocytes and the maternal inheritance of mtDNA. Next, we summarized the mtDNA abnormalities in oocytes derived from aging, diabetes, obesity, and assisted reproductive technology (ART) in an attempt to further elucidate the possible mechanisms underlying the decline in oocyte health. Because multiple infertility factors are often involved when an individual is infertile, a comprehensive understanding of the individual effects of each infertility-related factor on mtDNA is necessary. Herein, we consider the influence of infertility-related factors on the mtDNA of the oocyte as a collective perspective for the first time, providing a supplementary angle and reference for multi-directional improvement strategies of oocyte quality in the future. In addition, we highlight the importance of studying ART-derived mitochondrial abnormalities during every ART procedure.

Expecting more: the case for incorporating fertility services into comprehensive sickle cell disease care

Assisted reproductive technologies (ART) are not yet systematically available to people with sickle cell disease or their parents. Fertility care for these groups requires addressing sickle cell disease-associated infertility risks, fertility preservation options, pregnancy possibilities and outcomes, and, when needed, infertility treatment. People with a chance of having a child with sickle cell disease can use in-vitro fertilisation with preimplantation genetic testing to conceive a child unaffected by sickle cell disease. Also, parents of children with sickle cell disease can use this technology to identify embryos to become potential future matched sibling donors for stem cell transplant. In the USA, disparities in fertility care for the sickle cell disease community are especially stark. Universal screening of newborn babies' identifies sickle cell disease and sickle cell trait, guidelines direct preconception genetic carrier screening, and standard-of-care fertility preserving options exist. However, potentially transformative treatments and cures for patients with sickle cell disease are not used due to iatrogenic infertility concerns. In diversely resourced care settings, obstacles to providing fertility care to people affected by sickle cell disease persist. In this Viewpoint, we contend that fertility care should be incorporated into the comprehensive care model for sickle cell disease, supporting alignment of treatment goals with reproductive life plans and delivering on the promise of individualised high-quality care for people with sickle cell disease and their families. We consider the obligation to provide fertility care in light of medical evidence, with acknowledgment of formidable obstacles to optimising care, and powerful historical and ethical considerations.

BRCA, infertility, and fertility preservation: a review for counseling

BRCA mutations as a triggering factor in breast cancer have been reported to result in fertility problems and oocyte aging in young patients with cancer diagnosis. These patients are concerned about fertility problems and family planning before undergoing treatment modalities that may result in infertility. In this review, we conducted analysis of the literature on the association between BRCA mutations and infertility, possible fertility preservation options, and their safety and tried to gather results from different disciplines and points of view on the matter. Our aim is to provide a general summary of recent studies to provide further insight on the matter for counseling BRCA mutation carriers on fertility preservation methods and their implications.

Reproductive genomics of the mouse: implications for human fertility and infertility

Genetic analyses of mammalian gametogenesis and fertility have the potential to inform about two important and interrelated clinical areas: infertility and contraception. Here, we address the genetics and genomics underlying gamete formation, productivity and function in the context of reproductive success in mammalian systems, primarily mouse and human. Although much is known about the specific genes and proteins required for meiotic processes and sperm function, we know relatively little about other gametic determinants of overall fertility, such as regulation of gamete numbers, duration of gamete production, and gamete selection and function in fertilization. As fertility is not a binary trait, attention is now appropriately focused on the oligogenic, quantitative aspects of reproduction. Multiparent mouse populations, created by complex crossing strategies, exhibit genetic diversity similar to human populations and will be valuable resources for genetic discovery, helping to overcome current limitations to our knowledge of mammalian reproductive genetics. Finally, we discuss how what we know about the genomics of reproduction can ultimately be brought to the clinic, informing our concepts of human fertility and infertility, and improving assisted reproductive technologies.

Profiling the male germline genome to unravel its reproductive potential

OBJECTIVE

To identify specific germline mutations related to sperm reproductive competence, in couples with unexplained infertility.

DESIGN

In this retrospective study, couples were divided according to whether they had successful intracytoplasmic sperm injection outcomes (fertile) or not (infertile). Ancillary sperm function tests were performed on ejaculates, and whole exome sequencing was performed on spermatozoal DNA. Sperm aneuploidy and gene mutation profiles were compared between the 2 cohorts as well as according to the specific reasons for reproductive failure.

SETTING

Center for reproductive medicine at a major academic medical center.

PATIENT(S)

Thirty-one couples with negative infertility workups and normal semen parameters.

INTERVENTION(S)

Couples with mutations on fertilization- or embryo development-related genes were subsequently treated by assisted gamete treatment or microfluidics, respectively.

MAIN OUTCOME MEASURE(S)

Intracytoplasmic sperm injection cycle outcomes including fertilization, clinical pregnancy, and delivery rates.

RESULT(S)

Sperm aneuploidy was lower in the fertile group (4.0% vs. 8.4%). Spermatozoa from both cohorts displayed mutations associated with sperm-egg fusion (ADAM3A) and acrosomal development (SPACA1), regardless of reproductive outcome. The infertile cohort was then categorized according to the reasons for reproductive failure: absent fertilization, poor early embryo development, implantation failure, or pregnancy loss. Spermatozoa from the fertilization failure subgroup (n = 4) had negligible PLCζ presence (10% ± 9%) and gene mutations (PLCZ1, PIWIL1, ADAM15) indicating a sperm-related oocyte-activating deficiency. These couples were successfully treated by assisted gamete treatment in their subsequent cycles. Spermatozoa from the poor early embryo development subgroup (n = 5) had abnormal centrosomes (45.9% ± 5%), and displayed mutations impacting centrosome integrity (HAUS1) and spindle/microtubular stabilization (KIF4A, XRN1). Microfluidic sperm processing subsequently yielded a term pregnancy. Spermatozoa from the implantation failure subgroup (n = 7) also had abnormal centrosomes (53.1% ± 13%) and carried mutations affecting embryonic implantation (IL9R) and microtubule and centrosomal integrity (MAP1S, SUPT5H, PLK4), whereas those from the pregnancy loss subgroup (n = 5) displayed mutations on genes involved in trophoblast development (NLRP7), cell cycle regulation (MARK4, TRIP13, DAB2IP, KIF1C), and recurrent miscarriage (TP53).

CONCLUSION(S)

By assessing the sperm genome, we identified specific germline mutations related to various reproductive processes. This information may clarify elusive factors underlying reproductive competence and enhance treatment for couples with unexplained infertility.

Risk of genetic and epigenetic alteration in children conceived following ART: Is it time to return to nature whenever possible?

Assisted reproductive technology may influence epigenetic signature as the procedures coincide with the extensive epigenetic modification occurring from fertilization to embryo implantation. However, it is still unclear to what extent ART alters the embryo epigenome. In vivo fertilization occurs in the fallopian tube, where a specific and natural environment enables the embryo's healthy development. During this dynamic period, major waves of epigenetic reprogramming, crucial for the normal fate of the embryo, take place. Over the past decade, concerns relating to the raised incidence of epigenetic anomalies and imprinting following ART have been raised by several authors. Epigenetic reprogramming is particularly susceptible to environmental conditions during the periconceptional period; therefore, unphysiological conditions, including ovarian stimulation, in vitro fertilization, embryo culture, cryopreservation of gametes and embryos, parental lifestyle, and underlying infertility, have the potential to contribute to epigenetic dysregulation independently or collectively. This review critically appraises the evidence relating to the association between ART and genetic and epigenetic modifications that may be transmitted to the offspring.

ATAC-seq and RNA-seq analysis unravel the mechanism of sex differentiation and infertility in sex reversal chicken

BACKGROUND

Sex determination and differentiation are complex and delicate processes. In female chickens, the process of sex differentiation is sensitive and prone to be affected by the administration of aromatase inhibitors, which result in chicken sex reversal and infertility. However, the molecular mechanisms underlying sex differentiation and infertility in chicken sex reversal remain unclear. Therefore, we established a sex-reversed chicken flock by injecting an aromatase inhibitor, fadrozole, and constructed relatively high-resolution profiles of the gene expression and chromatin accessibility of embryonic gonads.

RESULTS

We revealed that fadrozole affected the transcriptional activities of several genes, such as DMRT1, SOX9, FOXL2, and CYP19A1, related to sex determination and differentiation, and the expression of a set of gonadal development-related genes, such as FGFR3 and TOX3, by regulating nearby open chromatin regions in sex-reversed chicken embryos. After sexual maturity, the sex-reversed chickens were confirmed to be infertile, and the possible causes of this infertility were further investigated. We found that the structure of the gonads and sperm were greatly deformed, and we identified several promising genes related to spermatogenesis and infertility, such as SPEF2, DNAI1, and TACR3, through RNA-seq.

CONCLUSIONS

This study provides clear insights into the exploration of potential molecular basis underlying sex differentiation and infertility in sex-reversed chickens and lays a foundation for further research into the sex development of birds.

Genetic variation in P-element dysgenic sterility is associated with double-strand break repair and alternative splicing of TE transcripts

The germline mobilization of transposable elements (TEs) by small RNA mediated silencing pathways is conserved across eukaryotes and critical for ensuring the integrity of gamete genomes. However, genomes are recurrently invaded by novel TEs through horizontal transfer. These invading TEs are not targeted by host small RNAs, and their unregulated activity can cause DNA damage in germline cells and ultimately lead to sterility. Here we use hybrid dysgenesis-a sterility syndrome of Drosophila caused by transposition of invading P-element DNA transposons-to uncover host genetic variants that modulate dysgenic sterility. Using a panel of highly recombinant inbred lines of Drosophila melanogaster, we identified two linked quantitative trait loci (QTL) that determine the severity of dysgenic sterility in young and old females, respectively. We show that ovaries of fertile genotypes exhibit increased expression of splicing factors that suppress the production of transposase encoding transcripts, which likely reduces the transposition rate and associated DNA damage. We also show that fertile alleles are associated with decreased sensitivity to double-stranded breaks and enhanced DNA repair, explaining their ability to withstand high germline transposition rates. Together, our work reveals a diversity of mechanisms whereby host genotype modulates the cost of an invading TE, and points to genetic variants that were likely beneficial during the P-element invasion.

Successful Live Twin Birth through IVF/ICSI from a Couple with an Infertile Father with Pericentric Inversion of Chromosome 9 (p12q13): A Case with a High Aneuploidy Rate

Evidence suggests that the pericentric inversion of chromosome 9 (inv(9)) does not affect the aneuploidy rate (38.5%) after IVF. Herein, we report a successful live female twin birth through IVF/ICSI with a high aneuploidy rate from a couple within which the infertile father has inv(9)(p12q13). A couple (a 34-year-old male and a 35-year-old female) was referred to our clinic due to infertility. The wife has a child with her previous husband. Results from the infertility workup of both parents were normal. Karyotyping revealed that the inv(9)(p12q13) of the father was the only cytogenetic abnormality. Preimplantation genetic testing for aneuploidies (PGT-A) after IVF/ICSI revealed a high aneuploidy rate (77%; 10/13). Two euploid blastocysts were transferred, resulting in a successful live female twin birth. The presented case highlights the possibility that inv(9)(p12q13) in males may impact the fertility and euploidy rate. PGT-A facilitates the selection of qualified blastocysts for the optimization of live-birth outcomes.

Delayed puberty, gonadotropin abnormalities and subfertility in male Padi2/Padi4 double knockout mice

BACKGROUND

Peptidylarginine deiminase enzymes (PADs) convert arginine residues to citrulline in a process called citrullination or deimination. Recently, two PADs, PAD2 and PAD4, have been linked to hormone signaling in vitro and the goal of this study was to test for links between PAD2/PAD4 and hormone signaling in vivo.

METHODS

Preliminary analysis of Padi2 and Padi4 single knockout (SKO) mice did not find any overt reproductive defects and we predicted that this was likely due to genetic compensation. To test this hypothesis, we created a Padi2/Padi4 double knockout (DKO) mouse model and tested these mice along with wild-type FVB/NJ (WT) and both strains of SKO mice for a range of reproductive defects.

RESULTS

Controlled breeding trials found that male DKO mice appeared to take longer to have their first litter than WT controls. This tendency was maintained when these mice were mated to either DKO or WT females. Additionally, unsexed 2-day old DKO pups and male DKO weanlings both weighed significantly less than their WT counterparts, took significantly longer than WT males to reach puberty, and had consistently lower serum testosterone levels. Furthermore, 90-day old adult DKO males had smaller testes than WT males with increased rates of germ cell apoptosis.

CONCLUSIONS

The Padi2/Padi4 DKO mouse model provides a new tool for investigating PAD function and outcomes from our studies provide the first in vivo evidence linking PADs with hormone signaling.

IL-22 regulates endometrial regeneration by enhancing tight junctions and orchestrating extracellular matrix

The uterine endometrium uniquely regenerates after menses, postpartum, or after breaks in the uterine layer integrity throughout women’s lives. Direct cell–cell contacts ensured by tight and adherens junctions play an important role in endometrial integrity. Any changes in these junctions can alter the endometrial permeability of the uterus and have an impact on the regeneration of uterine layers. Interleukin 22 (IL-22) is a cytokine that is recognized for its role in epithelial regeneration. Moreover, it is crucial in controlling the inflammatory response in mucosal tissues. Here, we studied the role of IL-22 in endometrial recovery after inflammation-triggered abortion. Fecundity of mice was studied in consecutive matings of the same animals after lipopolysaccharide (LPS) (10 µg per mouse)-triggered abortion. The fecundity rate after the second mating was substantially different between IL-22 knockout (IL-22^−/−) (9.1%) and wild-type (WT) (71.4%) mice (p < 0.05), while there was no difference between the groups in the initial mating, suggesting that IL-22 deficiency might be associated with secondary infertility. A considerable difference was observed between IL-22^−/− and WT mice in the uterine clearance following LPS-triggered abortion. Gross examination of the uteri of IL-22^−/− mice revealed non-viable fetuses retained inside the horns (delayed clearance). In contrast, all WT mice had completed abortion with total clearance after LPS exposure. We also discovered that IL-22 deficiency is associated with a decreased expression of tight junctions (claudin-2 and claudin-10) and cell surface pathogen protectors (mucin-1). Moreover, IL-22 has a role in the remodeling of the uterine tissue in the inflammatory environment by regulating epithelial–mesenchymal transition markers called E- and N-cadherin. Therefore, IL-22 contributes to the proper regeneration of endometrial layers after inflammation-triggered abortion. Thus, it might have a practical significance to be utilized as a treatment option postpartum (enhanced regeneration function) and in secondary infertility caused by inflammation (enhanced barrier/protector function).

Epigenetic regulation and T-cell responses in endometriosis – something other than autoimmunity

Endometriosis is defined as the presence of endometrial-like glands and stroma located outside the uterine cavity. This common, estrogen dependent, inflammatory condition affects up to 15% of reproductive-aged women and is a well-recognized cause of chronic pelvic pain and infertility. Despite the still unknown etiology of endometriosis, much evidence suggests the participation of epigenetic mechanisms in the disease etiopathogenesis. The main rationale is based on the fact that heritable phenotype changes that do not involve alterations in the DNA sequence are common triggers for hormonal, immunological, and inflammatory disorders, which play a key role in the formation of endometriotic foci. Epigenetic mechanisms regulating T-cell responses, including DNA methylation and posttranslational histone modifications, deserve attention because tissue-resident T lymphocytes work in concert with organ structural cells to generate appropriate immune responses and are functionally shaped by organ-specific environmental conditions. Thus, a failure to precisely regulate immune cell transcription may result in compromised immunological integrity of the organ with an increased risk of inflammatory disorders. The coexistence of endometriosis and autoimmunity is a well-known occurrence. Recent research results indicate regulatory T-cell (Treg) alterations in endometriosis, and an increased number of highly active Tregs and macrophages have been found in peritoneal fluid from women with endometriosis. Elimination of the regulatory function of T cells and an imbalance between T helper cells of the Th1 and Th2 types have been reported in the endometria of women with endometriosis-associated infertility. This review aims to present the state of the art in recognition epigenetic reprogramming of T cells as the key factor in the pathophysiology of endometriosis in the context of T-cell-related autoimmunity. The new potential therapeutic approaches based on epigenetic modulation and/or adoptive transfer of T cells will also be outlined.

Smoking and infertility: multivariable regression and Mendelian randomization analyses in the Norwegian Mother, Father and Child Cohort Study

OBJECTIVE

To investigate the association between smoking and infertility.

DESIGN

Prospective study.

SETTING

Nationwide cohort.

PATIENTS

28,606 women and 27,096 men with questionnaire and genotype information from the Norwegian Mother, Father, and Child Cohort Study.

INTERVENTION

Self-reported information on smoking (having ever smoked [both sexes], age at initiation [women only], cessation [women only], and cigarettes/week in current smokers [both sexes]) was gathered. Genetically predetermined levels or likelihood of presenting these traits were estimated for Mendelian randomization.

MAIN OUTCOME MEASURE

Infertility (time-to-pregnancy ≥12 months).

RESULTS

Having ever smoked was unrelated to infertility in women or men. Higher smoking intensity in women was associated with greater infertility odds (+1 standard deviation [SD, 48 cigarettes/week]: odds ratio [OR]crude, 1.19; 95% confidence interval [CI] 1.11-1.28; ORadjusted 1.12; 95% CI, 1.03-1.21), also after adjusting for the partner's tobacco use. Later smoking initiation (+1 SD [3.2 years]: ORcrude, 0.94; 95% CI, 0.88-0.99; ORadjusted 0.89; 95% CI, 0.84-0.95) and smoking cessation (vs. not quitting: ORcrude, 0.83; 95% CI, 0.75-0.91; ORadjusted, 0.83; 95% CI, 0.75-0.93) were linked to decreased infertility in women. Nevertheless, Mendelian randomization results were not directionally consistent for smoking intensity and cessation and were estimated imprecisely in the 2-sample approach. In men, greater smoking intensity was not robustly associated with infertility in multivariable regression and Mendelian randomization.

CONCLUSIONS

We did not find robust evidence of an effect of smoking on infertility. This may be due to a true lack of effect, weak genetic instruments, or other kinds of confounding.

Discovery of a novel mitochondrial DNA molecule associated with tetrad pollen sterility in potato

BACKGROUND

Tetrad sterility in potato is caused by a specific cytoplasm, called TSC_sto, derived from the Mexican wild tetraploid species Solanum stoloniferum. Different S. stoloniferum accessions crossed as females with S. tuberosum resulted in 12 fertile hybrids and 27 sterile hybrids exhibiting tetrad sterility.

RESULTS

Whole-mitochondrial-genome sequencing was performed for two fertile hybrids and three hybrids exhibiting tetrad sterility. Two to seven contigs, with the total assembly lengths ranging from 462,716 to 535,375 bp, were assembled for each hybrid. Unlike for the reference mitochondrial genome (cv. Désirée), two different recombinant-type contigs (RC-I and RC-II) were identified. RC-I featured by the rpl5-ψrps14 gene joined to the nad6 gene, generating a novel intergenic region. Using a PCR marker (P-3), we found that this intergenic region occurred exclusively in interspecific hybrids exhibiting tetrad sterility and in their parental S. stoloniferum accessions. A part of this intergenic sequence was expressed in the pollen. From a large survey in which P-3 was applied to 129 accessions of 27 mostly Mexican wild species, RC-I was found in diploid S. verrucosum and polyploid species. From eight accessions of S. verrucosum used as females, 92 interspecific hybrids were generated, in which only those carrying RC-I exhibited tetrad sterility.

CONCLUSIONS

RC-I was clearly associated with tetrad sterility, and the RC-I-specific intergenic region likely contains a causal factor of tetrad sterility.

Loss of mouse Y chromosome gene Zfy1 and Zfy2 leads to spermatogenesis impairment, sperm defects, and infertility

Using mice with Y chromosome deficiencies and supplementing Zfy transgenes, we, and others, have previously shown that the loss of Y chromosome Zfy1 and Zfy2 genes is associated with infertility and spermiogenic defects and that the addition of Zfy transgenes rescues these defects. In these past studies, the absence of Zfy was linked to the loss of other Y chromosome genes, which might have contributed to spermiogenic phenotypes. Here, we used CRISPR/Cas9 to specifically remove open reading frame of Zfy1, Zfy2, or both Zfy1 and Zfy2, and generated Zfy knockout (KO) and double knockout (DKO) mice. Zfy1 KO and Zfy2 KO mice were both fertile, but the latter had decreased litters size and sperm number, and sperm headshape abnormalities. Zfy DKO males were infertile and displayed severe spermatogenesis defects. Postmeiotic arrest largely prevented production of sperm and the few sperm that were produced all displayed gross headshape abnormalities and structural defects within head and tail. Infertility of Zfy DKO mice could be overcome by injection of spermatids or sperm directly to oocytes, and the resulting male offspring had the same spermiogenic phenotype as their fathers. The study is the first describing detailed phenotypic characterization of mice with the complete Zfy gene loss. It provides evidence supporting that the presence of at least one Zfy homolog is essential for male fertility and development of normal sperm functional in unassisted fertilization. The data also show that while the loss of Zfy1 is benign, the loss of Zfy2 is mildly detrimental for spermatogenesis.

Racial and Ethnic Variation in Genetic Susceptibility: Are Disparities in Infertility Prevalence and Outcomes more than Black and White?

Race, as a social construct without a clear genetic underpinning, is frequently referenced in medicine as predictor of multiple diseases including that of infertility. The authors will discuss how systematic racism can have downstream consequences ranging from overt physician bias to use of medical algorithms that may potentiate the same disparities they attempt to narrow. Then, the authors explore the utility and pragmatic use of genetic ancestry to estimate disease prevalence, instead of racial categories. Finally, the authors explore how health inequities, rooted in systematic racism, can influence disease heritability effectively advocating for research to disentangle the contributions of racism to genetic susceptibility in infertility.

Impaired leptin signaling causes subfertility in female zebrafish

Reproduction is an energetically costly event across vertebrates and tightly linked to nutritional status and energy reserves. In mammals, the hormone leptin is considered as a link between energy homeostasis and reproduction. However, its role in fish reproduction is still unclear. In this study, we investigated the possible role of leptin in the regulation of reproduction in zebrafish, using a loss of function leptin receptor (lepr) strain. Impaired leptin signaling resulted in severe reproductive deficiencies in female zebrafish. lepr mutant females laid significantly fewer eggs, with low fertilization rates compared to wild-type females. Folliculogenesis was not affected, but oocyte maturation and ovulation were disrupted in lepr mutants. Interestingly, the expression of luteinizing hormone beta (lhb) in the pituitary was significantly lower in mutant females. Analysis of candidate genes in the ovaries and isolated fully grown follicles revealed differential expression of genes involved in steroidogenesis, oocyte maturation and ovulation in the mutants, which are known to be regulated by LH signaling. Moreover, subfertility in lepr mutants could be partially restored by administration of human chorionic gonadotropin. In conclusion, our results show that leptin deficiency does not affect early stages of follicular development, but leptin might be essential in later steps, such as in oocyte maturation and ovulation. To our knowledge, this is the first time that leptin is associated to reproductive deficiencies in zebrafish.

Genome-Wide Differential DNA Methylomes Provide Insights into the Infertility of Triploid Oysters

Chromosomal incompatibility and gene expression changes would affect the development of polyploid gonad and gamete formation. The role of epigenetics like DNA methylation in reproductive development is fully demonstrated in diploid animals. The lack of polyploid species and the infertility of polyploid animals, especially the odd ploidy, limit the study of epigenetic regulation mechanism of polyploid reproduction. Fertile and infertile individuals exist in triploid Pacific oyster Crassostrea gigas, which provide an interesting model for studies on the effect of epigenetic regulation on gonadal development. The whole genome single base resolution DNA methylomes in gonads of triploid females α (F-3nα), triploid females β (F-3nβ), triploid males α (M-3nα), triploid hermaphrodite predominantly males (HPM-3n), diploid females (F-2n), and diploid males (M-2n) were generated by using bisulfite-sequencing. The overall DNA methylation profiles in gene regions and transposable regions of fertile and infertile triploid oysters were consistent with those of diploid oysters. The DNA methylation level of CG context decreased in infertile triploid oysters, with more hypomethylated than hypermethylated regions, and the opposite is true in fertile triploid oysters. Genes harbored with differentially methylated regions (DMRs) in infertile triploids were mainly related to the metabolism pathways and the signal pathways. Correlation analysis indicated that the expression of gene transcriptions was generally positively associated with DNA methylation in gene body regions, and DMRs in infertile triploid oysters played significant roles in gonadal development as a possible critical epigenetic regulator of gonadal development gene transcriptional activity. These findings indicate a potential relationship between DNA methylation variability and gene expression plasticity in newly formed polyploidy. As far as we know, this is the first study revealing the epigenetic regulation of gonadal development in invertebrates based on fertile and infertile models, meanwhile providing a new mentality to explore the regulatory mechanisms of infertility in triploids.

Chloroplast Genes Are Involved in The Male-Sterility of K-Type CMS in Wheat

The utilization of crop heterosis can greatly improve crop yield. The sterile line is vital for the heterosis utilization of wheat (Triticum aestivum L.). The chloroplast genomes of two sterile lines and one maintainer were sequenced using second-generation high-throughput technology and assembled. The nonsynonymous mutated genes among the three varieties were identified, the expressed difference was further analyzed by qPCR, and finally, the function of the differentially expressed genes was analyzed by the barley stripe mosaic virus-induced gene silencing (BSMV-VIGS) method. A total of 16 genes containing 31 nonsynonymous mutations between K519A and 519B were identified. There were no base mutations in the protein-encoding genes between K519A and YS3038. The chloroplast genomes of 519B and K519A were closely related to the Triticum genus and Aegilops genus, respectively. The gene expression levels of the six selected genes with nonsynonymous mutation sites for K519A compared to 519B were mostly downregulated at the binucleate and trinucleate stages of pollen development. The seed setting rates of atpB-silenced or ndhH-silenced 519B plants by BSMV-VIGS method were significantly reduced. It can be concluded that atpB and the ndhH are likely to be involved in the reproductive transformation of 519B.

Gene mutations associated with fertilization failure after in vitro fertilization/intracytoplasmic sperm injection

Fertilization failure during assisted reproductive technologies (ART) is often unpredictable, as this failure is encountered only after in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) have been performed. The etiology of fertilization failure remains elusive. More and more mutations of genes are found to be involved in human fertilization failure in infertile patients as high throughput sequencing techniques are becoming widely applied. In this review, the mutations of nine important genes expressed in sperm or oocytes, PLCZ1, ACTL7A, ACTL9, DNAH17, WEE2, TUBB8, NLRP5, ZP2, and TLE6, were summarized and discussed. These abnormalities mainly have shown Mendelian patterns of inheritance, including dominant and recessive inheritance, although de novo mutations were present in some cases. The review revealed the crucial roles of each reported gene in the fertilization process and summarized all known mutations and their corresponding phenotypes. The review suggested the mutations might become promising targets for precision treatments in reproductive medicine. Moreover, our work will provide some helpful clues for genetic counseling, risk prediction, and optimizing clinical treatments for human infertility by supplying the useful and timely information on the genetic causes leading to fertilization failure.

Aborting meiosis allows recombination in sterile diploid yeast hybrids

Hybrids between diverged lineages contain novel genetic combinations but an impaired meiosis often makes them evolutionary dead ends. Here, we explore to what extent an aborted meiosis followed by a return-to-growth (RTG) promotes recombination across a panel of 20 Saccharomyces cerevisiae and S. paradoxus diploid hybrids with different genomic structures and levels of sterility. Genome analyses of 275 clones reveal that RTG promotes recombination and generates extensive regions of loss-of-heterozygosity in sterile hybrids with either a defective meiosis or a heavily rearranged karyotype, whereas RTG recombination is reduced by high sequence divergence between parental subgenomes. The RTG recombination preferentially arises in regions with low local heterozygosity and near meiotic recombination hotspots. The loss-of-heterozygosity has a profound impact on sexual and asexual fitness, and enables genetic mapping of phenotypic differences in sterile lineages where linkage analysis would fail. We propose that RTG gives sterile yeast hybrids access to a natural route for genome recombination and adaptation.

Loss of basigin expression in uterine cells leads to subfertility in female mice†

Basigin (BSG) is a transmembrane glycoprotein involved in cell proliferation, angiogenesis, and tissue remodeling. BSG has been shown to be essential for male and female reproduction although little is known about its role in normal uterine function. To study the potential function of BSG in the female reproductive tract, we generated mice with conditional knockout of Bsg in uterine cells using progesterone receptor-Cre and hypothesized that BSG is required for normal pregnancy in mice. Fertility study data showed that the conditional knockout mice had significantly reduced fertility compared to controls. Ovarian function of the conditional knockout mice appeared normal with no difference in the number of superovulated oocytes collected or in serum progesterone levels between the conditional knockout and the control mice. Uterine tissues collected at various times of gestation showed increased abnormalities in implantation, decidualization, placentation, and parturition in the conditional knockout mice. Uterine cross sections on Day 5 of pregnancy showed implantation failure and abnormal uterine epithelial differentiation in a large proportion of the conditional knockout mice. There was a compromised decidual response to artificial decidualization stimuli and decreased mRNA and protein levels for decidualization genes in the uteri of the conditional knockout mice. We also observed altered protein expression of monocarboxylate transporter 1 (MCT1), as well as impaired angiogenesis in the conditional knockout uteri compared to the controls. These results support that BSG is required for successful pregnancy through its functions in implantation and decidualization.