Gamete Production Research Articles

Evidence of Sexual Reproduction in Out-Planted Coral Colonies

Intervention techniques to restore coral communities have become an important management tool to help recover and rehabilitate damaged reefs. The direct transplantation of healthy coral fragments is the most common method; however, there is controversy in the long-term success, as using coral clones may diminish the genetic diversity of the coral population. Genetic recombination can be achieved when the coral colony produces gametes and eventually reproduces; therefore, it is important to provide evidence that restored colonies produce gametes as their naturally recruited counterparts with similar colony size (age). Natural and restored Pocillopora coral colonies of the same size range (between 40 and 50 cm in diameter) were tagged and sampled during the rainy season to determine gamete maturation. Our results show no differences in the reproductive activity among colonies: natural and restored coral colonies matured gametes from June to October, with a peak in sexually active coral colonies in July. Also, gamete malformation was not observed. During the gamete production period, the area’s temperature ranged from 27.9 to 30.02 °C. The results’ evidence that coral colonies formed through active restoration contribute not only to the increase in live coral cover as seen in previous studies but potentially contribute in the medium term (>5 years after out-planting) to the production of larvae and local and subsidiary recruitment, since they exhibit the same reproductive patterns as their naturally formed counterparts and no differences in the reproductive activity among coral colonies. Therefore, long-term coral restoration projects contribute to maintaining the live coral cover and the genetic diversity in the region, eventually rehabilitating the coral community.

Metabolic regulation of proteome stability via N-terminal acetylation controls male germline stem cell differentiation and reproduction

The molecular mechanisms connecting cellular metabolism with differentiation remain poorly understood. Here, we find that metabolic signals contribute to stem cell differentiation and germline homeostasis during Drosophila melanogaster spermatogenesis. We discovered that external citrate, originating outside the gonad, fuels the production of Acetyl-coenzyme A by germline ATP-citrate lyase (dACLY). We show that this pathway is essential during the final spermatogenic stages, where a high Acetyl-coenzyme A level promotes NatB-dependent N-terminal protein acetylation. Using genetic and biochemical experiments, we establish that N-terminal acetylation shields key target proteins, essential for spermatid differentiation, from proteasomal degradation by the ubiquitin ligase dUBR1. Our work uncovers crosstalk between metabolism and proteome stability that is mediated via protein post-translational modification. We propose that this system coordinates the metabolic state of the organism with gamete production. More broadly, modulation of proteome turnover by circulating metabolites may be a conserved regulatory mechanism to control cell functions.

Frequency, morbidity and equity - the case for increased research on male fertility.

Currently, most men with infertility cannot be given an aetiology, which reflects a lack of knowledge around gamete production and how it is affected by genetics and the environment. A failure to recognize the burden of male infertility and its potential as a biomarker for systemic illness exists. The absence of such knowledge results in patients generally being treated as a uniform group, for whom the strategy is to bypass the causality using medically assisted reproduction (MAR)techniques. In doing so, opportunities to prevent co-morbidity are missed and the burden of MAR is shifted to the woman. To advance understanding of men's reproductive health, longitudinal and multi-national centres for data and sample collection are essential. Such programmes must enable an integrated view of the consequences of genetics, epigenetics and environmental factors on fertility and offspring health. Definition and possible amelioration of the consequences of MAR for conceived children are needed. Inherent in this statement is the necessity to promote fertility restoration and/or use the least invasive MAR strategy available. To achieve this aim, protocols must be rigorously tested and the move towards personalized medicine encouraged. Equally, education of the public, governments and clinicians on the frequency and consequences of infertility is needed. Health options, including male contraceptives, must be expanded, and the opportunities encompassed in such investment understood. The pressing questions related to male reproductive health, spanning the spectrum of andrology are identified in the Expert Recommendation.

Germ cell recovery, cryopreservation and transplantation in the California white sturgeon, Acipenser transmontanus

The white sturgeon (Acipenser transmontanus) is the largest freshwater fish in North America. Because of the unique life history characteristics of sturgeon, including longevity, late maturation and long spawning intervals, their aquaculture can be a significant investment of resources. As a result of habitat loss and overharvesting, natural populations of white sturgeon are threatened and there is a growing effort to improve conservation aquaculture programs. Germ cell transplantation is an innovative technology previously demonstrated in a variety of fish species to be able to produce a surrogate broodstock. The technique relies upon optimal donor germ cell recovery and transplantation into a recipient fish. In this study, we developed and optimized the harvest of donor cells for germline transplantation and evaluated methods for ovary cryopreservation for the first time in the white sturgeon. We found that harvesting gonads from juveniles between the ages of 1.5 and 2.5-years resulted in reliably high proportions of pre-meiotic cells regardless of sex, a critical feature for using white sturgeon for transplantation studies since the species shows no distinguishing external sex characteristics. From the viable cells, we identified germline cells using immunolabeling with the antibody DDX4, a marker specific to the germline. For in vivo tracking of donor cells during transplantations, gonadal cells were stained with a long half-life non-toxic cell membrane dye, PKH26, and microinjected into the peritoneal cavity of newly hatched white sturgeon larvae. Larvae were reared until 3 months post-transplantation to monitor for colonization and proliferation of PKH26-labeled cells within the recipient larval gonads. Furthermore, viable cell detection, assessment of germline-specificity, and transplantation was determined for cells recovered from cryopreserved ovarian tissue from sexually immature females. Transplantations using cells cryopreserved with media supplemented with dimethyl sulfoxide (DMSO) rather than ethylene glycol (EG) demonstrated the highest number of PKH26-labeled cells distributed along the gonadal ridges of the larval recipient. Determining optimal methods of tissue cryopreservation, and germ cell recovery and transplantation are foundational to the future development of germ cell transplantation as a strategy to improve the aquaculture and conservation of this species. Our study demonstrates that conservation actions, such as surrogate breeding, could be utilized by hatcheries to retain or improve natural gamete production without genetic modification, and provide an encouraging approach to the management of threatened sturgeon species.

Canopy architecture and diurnal CO2 uptake in male and female clones of yerba‐mate cultivated in monoculture and agroforestry

AbstractSecondary sexual dimorphism (SSD) in flowering plants is expressed by sexual differences of characters that are not directly related to gamete production. The leaf C/N ratio, photosynthetic traits or clonal responses have never been studied in relation to SSD in yerba‐mate. It was hypothesized that leaf and plant photosynthesis are higher in female than in male individuals because females must supply photoassimilates to compensate for the additional reproductive investments of SSD in biomass. Here, we investigated how two contrasting light environments (monoculture—MO and agroforestry—AFS) and plant genders change leaf and plant photosynthesis, plant architecture, leaf and branch biomass production and C and N investments of two male and two female clones. To model the 3D yerba‐mate structure, virtual trees were constructed using measurements of plant morphology using VPlant modelling software. The light‐response curves of leaf CO2 assimilation were used to model instantaneous leaf and daily plant photosynthesis. Photosynthetic traits derived from light‐response curves did not differ between MO and AFS. Some architectural traits were segregated sexually only in MO, while some physiological ones only in AFS. Leaf photosynthesis was higher in females than in males in AFS over a large part of the diurnal cycle, but SSD was not expressed in carbon gains at plant or daily scales. Leaf C/N ratio was higher in MO than in AFS, indicating MO as an ecosystem with higher degree of environmental degradation. Female clones had leaves with lower C/N ratio than males in both systems, relating to higher leaf photosynthesis on an area basis in females. SSD expressed in leaf photosynthesis over a large part of the diurnal cycle in AFS was not observed in carbon gains at plant or daily scales, indicating that the integration of physiology and architecture equalized the gender specificities. The insensitivity of photosynthetic traits derived from light‐response curves indicated acclimation of yerba‐mate leaves to a wide range of incoming light.

Glial cell line-derived neurotrophic factor (GDNF) is essential for colonization and expansion of turbot (Scophthalmus maximus) germ cells in recipients and in vitro culture

Germ cell transplantation (GCT) is a promising biotechnology that enables the production of donor-derived gametes in surrogate recipients. It plays a crucial role in the protection of endangered species, the propagation of elite species with desired traits, and long-term preservation of genetic resources. This significance is particularly pronounced when GCT is synergistically employed with cryopreservation techniques. However, GCT often encounters challenges due to low colonization rates and, in some cases, complete loss of donor cells in recipients. Glial cell line-derived neurotrophic factor (GDNF) plays a pivotal role in sustaining the self-renewal of spermatogonial stem cells (SSCs) in mammals. Additionally, it has been shown to promote the proliferation of spermatogonia in vitro cultures in certain animal species. In turbot (Scophthalmus maximus), we found that the expressions of gdnf and gfrα1a were predominantly observed in spermatogonia rather than somatic cells, which differed from their expression patterns in mammals. The efficiency of exogenous spermatogonia transplantation in Japanese flounder (Paralichthys olivaceus) larvae could be substantially enhanced by incubating donor cells from turbot with 100 ng/ml GDNF prior to transplantation. This led to a noteworthy increase in the colonization rate, rising from 33%-50%–61.5%. Additionally, the addition of 20 ng/ml GDNF in cell medium could also promote the proliferation of turbot germ cells in vitro. These results demonstrated the gdnf in turbot testis expression characteristics and suggested that addition of GNDF could be an effective way to improve the GCT efficiency and promote the germ cells expansion during in vitro culture.

Trace elements in bivalve shells: How “vital effects” can bias environmental studies

We report on the concentrations of rare earths (REE), Y, Mg, Mn, Cu, Zn, Sr, Ba, Pb and U in a series of wild scallops (Placopecten magellanicus) collected alive on the same day in Saint Pierre et Miquelon (a French archipelago located south of Newfoundland) and ranging in age from 2 to about 20 years. We analyzed representative fragments from the entire last annual shell growth increment of each animal to assess changes in trace element incorporation with age.No correlation with the age of the animals was obtained for Sr and Mn concentrations, which are quite variable from one individual to another, even of similar age. On the other hand, for REE, Y, Cu, Zn, Ba and U, the concentrations measured in the last annual growth increment formed by animals aged 2 to 7 years are similar. From 8 years of age, the concentrations of these elements increased very strongly (for example for Yb, almost by an order of magnitude between 8 and 20 years of age), and possibly with some variation between individuals of the same age. Two elements show a different behavior: Mg concentrations in the shell margins increase continuously with the age of the animals; Pb concentrations are scattered but seem to decrease with the age of the animals.This turning point in the behavior of the elements from 8 years of age coincides with major metabolic changes, since at this age wild P. magellanicus from Newfoundland reduce their growth, in favor of gamete production. Our results demonstrate that metabolic activity of the animals largely controls the incorporation of many trace elements into the shells. These results demonstrate that the age of the animals must be taken into account when their shells are used to study pollution or (paleo) environmental condition.

Evaluation of the effects of the recommended oral dose of diflubenzuron on bovine sperm and oocyte quality using CASA and OPU-IVEP.

The aim of this study was to evaluate potential effects of diflubenzuron on the production and quality of gametes, and on in vitro embryo production (IVEP) outcomes, in cattle. Two experiments were performed, the first to evaluate effects on semen, and the second on cumulus-oocyte complexes (COC) and on IVEP. Nelore (Bos taurus indicus) bulls (n = 14) or heifers (n = 16) were allocated into control (CG) or treatment (DIF) groups. All groups received a mineral mix supplement added (DIF) or not (CG) with diflubenzuron (30 mg/head/day), during 8 weeks. Animals were weighed and blood samples were collected throughout the experimental period. Every other week, bulls were subjected to semen collection and heifers to transvaginal ultrasound-guided follicle aspiration sessions. Semen underwent physical and morphological evaluation, and samples were stored for further computer-assisted sperm analysis. The COC recovered were evaluated according to morphology and those classified as viable were sent to an IVEP laboratory. Diflubenzuron had no effect (P > 0.05) on average body weight or in any blood hematological or biochemical endpoints, regardless of gender. In experiment 1, there was no difference (P > 0.05) between DIF and CG groups for sperm concentration, morphology, or kinetics. In experiment 2, there was also no effect of diflubenzuron on the number of total, viable, or grade I oocytes, as well as on cleavage or blastocyst rates (P > 0.05). In summary, the oral administration of diflubenzuron, within the recommended dose, has no short-term negative effects on sperm production and quality or on oocyte yield and developmental potential in vitro, in cattle.

P-719 Evaluation of genetic risk of apparently balanced chromosomal rearrangement carriers by breakpoint characterization

Abstract Study question What are breakpoint characteristics of ABCR carriers? What are the genetic risks of ABCR carriers caused by chromosome rearrangements? Summary answer We analyzed the characteristics of ABCR's breakpoints and found that heterogeneous deletion of some AD disease-related genes may not result in clinical phenotype. What is known already ABCRs are common chromosomal abnormalities. People with ABCRs generally lack any visible abnormal features; however, during childbirth, the abnormal pairing and missegregation of homologous chromosomes can lead to the production of unbalanced gametes, resulting in spontaneous abortion or the birth of children with chromosomal disorders. Prenatal diagnosis or preimplantation diagnosis can effectively prevent the birth of children with unbalanced chromosome rearrangements, but no substantial data has been collected to report on the characteristics and potential genetic risks of the chromosome breakage caused by the rearrangement. Study design, size, duration This is a retrospective study of 2441 breakpoints in 1219 ABCR carriers who underwent Preimplantation Genetic Testing (PGT) at the Reproductive and Genetic Hospital of Citic-Xiangya from August 1, 2016 to December 31, 2021. Participants/materials, setting, methods All patients in this study sought PGT treatment due to primary or secondary infertility caused by ABCRs. To characterize the chromosome breakpoints, the MicroSeq technique, which involves chromosome microdissection and next generation sequencing, was employed. Additionally, gap-junction PCR and Sanger sequencing were utilized to further validate some of the breakpoints. Main results and the role of chance In this study, we retrospectively analyzed 2441 chromosome rearrangement breakpoint MicroSeq localization data from 1219 ABCR carriers, including 2364 breakpoint regions in 1182 reciprocal translocations, 68 breakpoint regions in 34 inversions, and 9 breakpoint regions in 3 insertional translocations. We not only identified 8q24.13, 11q11.23, and 22q11.21 as previously reported hotspots of chromosomal balanced rearrangement breaks, but also identified the 10 Mb region of 12q24.13-q24.3 as a possible rare region of balanced rearrangement breaks. the average range of breakpoints identified by MicroSeq technology was only within 3.8 Kb, which clarified 95.82% (2339/2441) of balanced chromosomal rearrangements as to whether they broke genes or not. We identified 960 genes that were interrupted, of which 53 genes with autosomal dominant mode of inheritance (AD) were interrupted. Clinical phenotypic evaluation of these patients carrying interrupted AD genes identified that some of the AD genetic interruptions may not have a clinical phenotype. Limitations, reasons for caution MicroSeq cannot precisely pinpoint breakpoints to the gene or single base level. Moreover, carriers of ABCRs were not comprehensively assessed for other clinical characteristics, and the alteration in function of the known Haploinsufficiency gene could not be confirmed. Additionally, the position effect of the breakpoints has not been evaluated. Wider implications of the findings This investigation offers a reference for evaluating the pathogenicity and genetic risks of protein-truncation mutations in some AD genes. Trial registration number Not applicable

P-788 Embryo vitrification affects the epigenome of preimplantation embryos and the effects are inherited by the female offsprings.

Abstract Study question How does embryo vitrification regulates the transcriptome of preimplantation embryos through epigenetic regulation and how are the effects transmitted to the female offsprings? Summary answer Embryo vitrification changed the DNA methylation level of preimplantation embryo and disturbed glycolipid metabolism of female offsprings in mice. What is known already Vitrification is a type of embryo cryopreservation increasingly frequently used clinically. The effect of embryo freezing on the health of offspring has been widely concerned. Some clinical studies have shown that offspring obtained from frozen embryo transplantation has higher birth weight and may be at higher risk of certain birth defects, increased risk of type 1 diabetes and cancer. But not all studies agree. The offspring safety of vitrification needs further follow-up research. Mouse model is a helpful tool for us to carry up follow-up study and explore mechanism. Study design, size, duration After superovulation and mating of ICR mice, we obtained 8-Cell embryos. In Vitrify Group, the 8-Cell embryos underwent vitrification and thawing and culture in vitro till blastocysts. In InVitro Group, the 8-Cell embryos were directly cultured in vitro till blastocysts. We transplanted these blastocysts into surrogate mice to get offspring of InVitro and Vitrify. Along with offspring of natural conception (NC), we observed their growth and development and glycolipid metabolism until 18 weeks old. Participants/materials, setting, methods Single embryo RNA-seq and Whole Genome Bisulfite Sequencing (WGBS) were performed to get transcriptome and DNA methylation atlas. Immunofluorescence of blastocysts was performed to test level of 5mC/5hmC and Tet2. Glucose and insulin tolerance test (GTT/ITT), serum lipid level test were performed on offspring to examine the glycolipid metabolism status. Liver transmission electron microscope photographs were take to observe ultramicrostructure. Liver RNA-seq and WGBS were performed to verify the variation on pathways concerning glycolipid metabolism. Main results and the role of chance Pseudo-time analysis from RNA-seq of 16-Cell, morula and blastocyst showed a relative developmental time lag in Vitrify. Differentially expressed genes (DEGs) of vitrify group at the blastocyst stage are mainly enriched in lipid metabolism, insulin signal, TOR signal regulation, gamete production related DNA methylation pathways. GSEA analysis revealed down-regulation of insulin response pathway genes. WGBS showed a trend of genome-wide methylation increase in vitrify group. Immunofluorescence confirmed this observation as the fluorescence intensity ratio of 5mC/5hmC was increased. RNA-seq, qPCR and western-blot showed a lower expression level of Tet2. These results suggested that the demethylation was insufficient in vitrify group. Blastocyst differentially methylated genes (DMRs) from WGBS were enriched in insulin response pathways. In offspring, birth weight of Vitrify offspring is higher than InVitro. GTT and ITT showed an elevated level of AUC in Vitrify 10-week-female, indicating an impaired glucose tolerance. And the fasting serum cholesterol level was elevated in Vitrify 10-week-female, indicating an impaired lipid metabolism. Under transmission electron microscope, we saw swollen mitochondria in liver of Vitrify 10-week-female. We extracted RNA from 10-week-female for RNA-seq, DEGs were enriched in cholesterol biosynthesis pathway. We extracted DNA from 10-week-female for WGBS, DEGs were enriched in cAMP and AMPK signaling pathway. Limitations, reasons for caution We have not confirm the precise molecular site affected by vitrification, clarify the mechanism and conduct the rescue test yet, which we are currently working on. This study is just the first step in this direction, and more efforts are needed. Wider implications of the findings Although more clinical trials and basic science studies are required, our findings provide valuable information for preventive and clinical decisions, as ‘freeze-all’ strategy springs up in many centers. Embryo vitrification needs more cautious consideration. Optimizing embryo vitrification protocols are needed according to the mechanism to minimize unwanted effects. Trial registration number 2021YFC2700601

In silico study to unravel molecular networking of melatonin in the regulation of gametogenesis.

Melatonin, a pineal hormone, has potential role on steroidogenesis, growth and maturation of sperm and ovum during gametogenesis. The possible use of this indolamine as an antioxidant in the production of good quality gametes opens up a new area of current research. Nowadays, a large number of reproductive dysfunctions like infertility, failure in fertilization due to gametic malformations are major concern worldwide. So, understanding molecular mechanisms including interacting genes and their action is a prerequisite to the therapeutic approach against these issues. The aim of present bioinformatic study is the detection of molecular network concerning therapeutic potential of melatonin in gametogenesis. It includes target genes identification, gene ontology, KEGG pathway enrichment, network analysis, prediction of signaling pathways and molecular docking. We obtained common top 52 targets of melatonin in the process of gametogenesis. They are involved in biological processes related to the development of gonads and primary sexual characteristics, sex differentiation. We took top ten pathways out of total 190 enriched pathways for further analysis. Subsequently, principal component analysis also revealed that among top ten hub targets (TP53, CASP3, MAPK1, JUN, ESR1, CDK1, CDK2, TNF, GNRH1, CDKN1A) only TP53, JUN and ESR1were significantly interacted with melatonin on the basis of squared cosine value. So, present in silico investigation provides considerable information on the interactive network between therapeutic targets of melatonin along with the involvement of intracellular signalling cascade regulating biological processes associated with the gametogenesis. This novel approach may be pertinent in improving modern research on reproductive dysfunctions associated abnormalities.

Transcriptomic profiles reveal differences in gene expression between the testes and epididymis in stallions

Spermatogenesis and sperm maturation take place in the testes and epididymis, respectively. These complex physiological processes are regulated by multiple genes, which have not been studied in the stallion. In this study, Illumina sequencing was used to analyze the transcriptomes of the testes, head, body and tail of the epididymis from three reproductively normal stallions. The mRNA was extracted and the libraries were generated using Next Generation Sequencing (NGS). The expression patterns of differentially expressed genes (DEGs) in the testes and epididymis were determined by bioinformatics analysis. Gene Ontology (GO) enrichment analysis of DEGs was implemented and gene length bias was corrected. Differentially expressed genes were compared between the different segments of the epididymis and the testis (control tissue). GO-terms with adjusted p < 0.05 were considered significantly enriched. Among the four libraries, 18,732 genes were identified. Of those, 6,574 genes (39.1%) were tissue-specific. The distribution of tissue-specific genes was 14.2 % in the testes, 2.2 % in the epididymal head, 1.1 % in the epididymal body, and 1.4 % in the epididymal tail. Compared with testicular tissue, there were 13,349 DEGs (5,595 up-regulated and 7,754 down-regulated) in the epidydimal head, 14,207 DEGs (5,884 up-regulated and 8,323 down-regulated) in the epididymal body, and 14,822 DEGs (5,842 up-regulated and 8,980 down regulated) in the epididymal tail. In the epididymal head,the main downregulated terms were male gamete generation (224 DEGs), spermatogenesis (224 DEGs), organelle fission (264 DEGs), sexual reproduction (343 DEGs) and nuclear division (233 DEGs). The main upregulated terms were associated with the ribosome (322 DEGs), lymphocyte activation (226 DEGs), and cytosolic part (104 DEGs). In the epididymal body, the most significantly downregulated terms were male gamete generation (232 DEGs), spermatogenesis (232 DEGs), sexual reproduction (358 DEGs), cilium morphogenesis (151 DEGs) and cilium (235 DEGs). The most significantly upregulated terms were lysosome (150 DEGs), lytic vacuole (150 DEGs), positive regulation of locomotion (197 DEGs), cytosolic ribosome (71 DEGs), vacuole (182 DEGs). In the epididymal tail, the most significantly downregulated terms were male gamete generation (239 DEGs), spermatogenesis (193 DEGs), cilium (253 DEGs), ciliary part (186 DEGs), cilium morphogenesis (158 DEGs). The most significantly upregulated terms were associated with the ribosome (438 DEGs) and cytosolic part (109 DEGs). In summary, we found decreased expression of genes involved in gamete production, and increased expression of genes involved in protein synthesis, immunity and sperm transport in different segments of the epididymis. These findings provide genome-wide mRNA expression profiles for the horse epididymis and testes, providing a biological basis for future research on stallion fertility.

Artificial intelligence algorithms for optimizing assisted reproductive technology programs: A systematic review

Artificial intelligence (AI) has been experiencing rapid growth in recent years, and numerous applications are improving the single-step efficiency of the whole assisted reproductive technology (ART) procedure. In this review, we collected all the algorithms supplying ART and selected those supporting the clinical assistance to the procedure up to the successful attempt. Those with a clear role in improving ART performances were further selected. We found a questionnaire-based algorithm identifying patients at risk for endometriosis with early management and better fertility outcome. An algorithm can detect the values of simple gamete production (male) and reservoir (female) according to gradual scale allocation, and display themas normal or abnormal, spontaneousor stimulated gamete production. This can provide significant benefits for infertile couples undergoing diagnostic and therapeutic journeys. The calculators for the starting dose of gonadotropins and the trigger timing during controlled ovarian stimulation make clinical management more efficient. With the application of AI in ART, the ability to determine the optimal number of metaphase II oocytes required for blastocyst formation and number of oocytes needed for embryo production has been significantly improved. The calculation of the implantation rate as proposed in different calculators, using the ultrasound of endometrial vascularization or the age and euploidy of the embryo transferred, may provide further advancement in managing the ART procedure with more participation from the couples to increase the efficacy of the procedures. Finally, the calculator of presumptive success with an ART program based on couples or medical center profiling and efficiency is of tremendous comfort to couples. In conclusion, algorithms and machine learning development in human reproduction are growing daily with evident benefits. Infertility treatments by in vitro fertilization (IVF) are assisted by several algorithms that improve the efficiency of each procedure step, making IVF program’s management more effortless.

The IVG ‘relatedness paradox’: researchers should mind speculation

Companies and academic laboratories are pursuing the production of gametes from stem cells. Researchers should be active participants in discussions about speculative scenarios, to avoid this endeavor to accommodate genetic parenthood undermines the value it is meant to serve, because of either unrealistic or insufficient ethical reflection.

Notch pathway is required for protection against heat stress in spermatogonial stem cells in medaka.

Gamete production is a fundamental process for reproduction; however, exposure to stress, such as increased environmental temperature, can decrease or even interrupt this process, affecting fertility. Thus, the survival of spermatogonial stem cells (SSCs) is crucial for the recovery of spermatogenesis upon stressful situations. Here, we show that the Notch pathway is implicated in such survival, by protecting the SSCs against thermal stress. First, we corroborated the impairment of spermatogenesis under heat stress in medaka, observing an arrest in metaphase I at 10days of heat treatment, an increase in the number of spermatocytes, and downregulation of ndrg1b and sycp3. In addition, at 30days of treatment, an interruption of spermatogenesis was observed with a strong loss of spermatocytes and spermatids. Then, the exposure of adult males to thermal stress condition induced apoptosis mainly in spermatogenic and supporting somatic cells, with the exception of the germinal region, where SSCs are located. Concomitantly, the Notch pathway-related genes were upregulated, including the ligands (dll4, jag1-2) and receptors (notch1a-3). Moreover, during thermal stress presenilin enhancer-2 (pen-2), the catalytic subunit of γ-secretase complex of the Notch pathway was restricted to the germinal region of the medaka testis, observed in somatic cells surrounding type A spermatogonia (SGa). The importance of Notch pathway was further supported by an ex vivo approach, in which the inhibition of this pathway activity induced a loss of SSCs. Overall, this study supports the importance of Notch pathways for the protection of SSCs under chronic thermal stress.

Review: Embryonic stem cells as tools for in vitro gamete production in livestock.

The goal of in vitro gametogenesis is to reproduce the events of sperm and oocyte development in the laboratory. Significant advances have been made in the mouse in the last decade, but evolutionary divergence from the murine developmental program has prevented the replication of these advances in large mammals. In recent years, intensive work has been done in humans, non-human primates and livestock to elucidate species-specific differences that regulate germ cell development, due to the number of potential applications. One of the most promising applications is the use of in vitro gametes to optimize the spread of elite genetics in cattle. In this context, embryonic stem cells have been posed as excellent candidates for germ cell platforms. Here, we present the most relevant advances in in vitro gametogenesis of interest to livestock science, including new types of pluripotent stem cells with potential for germline derivation, characterization of the signaling environment in the gonadal niche, and experimental systems used to reproduce different stages of germ cell development in the laboratory.

Understanding the genetics of human infertility

Reproduction involves a wide range of biological processes, including organ formation and development, neuroendocrine regulation, hormone production, and meiosis and mitosis. Infertility, the failure of reproduction, has become a major issue for human reproductive health and affects up to one in seven couples worldwide. Here, we review various aspects of human infertility, including etiology, mechanisms, and treatments, with a particular emphasis on genetics. We focus on gamete production and gamete quality, which is the core of successful reproduction. We also discuss future research opportunities and challenges to further expand our understanding of human infertility and improve patient care by providing precision diagnosis and personalized treatments.

High Temperature-Induced Spindle Destabilization Results in Aborted Pollen Production in Populus

High temperature can induce the production of 2n gametes and aborted pollen during microsporogenesis in Populus canescens. However, the mechanism by which high temperature induces pollen abortion remains unknown. Here, pollen abortion was induced by exposing male flower buds of P. canescens to 38 and 41 °C; pollen morphology, meiotic abnormalities, defects of the meiotic microtubular cytoskeleton, and tapetum development were characterized. We found that the dominant meiotic stage, temperature, and duration of treatment significantly affected the percentage of high temperature-induced aborted pollen. Damaged spindle microtubules and depolymerized microtubular cytoskeletons were observed, which resulted in many lagging chromosomes at anaphase I and II as well as aneuploid male gametes and micronuclei, thereby generating aborted pollen grains. Tapetum disintegration was also delayed. The anther dehisced normally, and some viable pollen grains were released. However, no sufficient evidence showed that the delayed degradation of the tapetum was responsible for pollen abortion.

Pluripotent, germ cell competent adult stem cells underlie cnidarian regenerative ability and clonal growth

In most animals, pluripotency is irreversibly lost post gastrulation. By this stage, all embryonic cells have already committed either to one of the somatic lineages (ectoderm, endoderm, or mesoderm) or to the germline. The lack of pluripotent cells in adult life may be linked to organismal aging. Cnidarians (corals and jellyfish) are an early branch of animals that do not succumb to age, but the developmental potential of their adult stem cells remains unclear. Here, we show that adult stem cells in the cnidarian Hydractinia symbiolongicarpus (known as i-cells) are pluripotent. We transplanted single i-cells from transgenic fluorescent donors to wild-type recipients and followed them invivo in the translucent animals. Single engrafted i-cells self-renewed and contributed to all somatic lineages and gamete production, co-existing with and eventually displacing the allogeneic recipient's cells. Hence, a fully functional, sexually competent individual can derivefrom a single adult i-cell. Pluripotent i-cells enable regenerative, plant-like clonal growth in these animals.

Meiotic cells escape prolonged spindle checkpoint activity through kinetochore silencing and slippage.

To prevent chromosome mis-segregation, a surveillance mechanism known as the spindle checkpoint delays the cell cycle if kinetochores are not attached to spindle microtubules, allowing the cell additional time to correct improper attachments. During spindle checkpoint activation, checkpoint proteins bind the unattached kinetochore and send a diffusible signal to inhibit the anaphase promoting complex/cyclosome (APC/C). Previous work has shown that mitotic cells with depolymerized microtubules can escape prolonged spindle checkpoint activation in a process called mitotic slippage. During slippage, spindle checkpoint proteins bind unattached kinetochores, but the cells cannot maintain the checkpoint arrest. We asked if meiotic cells had as robust of a spindle checkpoint response as mitotic cells and whether they also undergo slippage after prolonged spindle checkpoint activity. We performed a direct comparison between mitotic and meiotic budding yeast cells that signal the spindle checkpoint through two different assays. We find that the spindle checkpoint delay is shorter in meiosis I or meiosis II compared to mitosis, overcoming a checkpoint arrest approximately 150 minutes earlier in meiosis than in mitosis. In addition, cells in meiosis I escape spindle checkpoint signaling using two mechanisms, silencing the checkpoint at the kinetochore and through slippage. We propose that meiotic cells undertake developmentally-regulated mechanisms to prevent persistent spindle checkpoint activity to ensure the production of gametes.