Ready for renascence in mosquito: The regulation of gene expression in Plasmodium sexual development

Malaria remains one of the most perilous vector-borne infectious diseases for humans globally. Sexual gametocyte represents the exclusive stage at which malaria parasites are transmitted from the vertebrate to the Anopheles host. The feasible and effective approach to prevent malaria transmission is by addressing the sexual developmental processes, that is, gametocytogenesis and gametogenesis. Thus, this review will comprehensively cover advances in the regulation of gene expression surrounding the transmissible stages, including epigenetic, transcriptional, and post-transcriptional control.

Gene expression profiles of Japanese precious coral Corallium japonicum during gametogenesis

Background

Corallium japonicum, a prized resource in Japan, plays a vital role in traditional arts and fishing industries. Because of diminished stock due to overexploitation, ongoing efforts are focused on restoration through transplantation. This study aimed to enhance our understanding of the reproductive biology of these valuable corals and find more efficient methods for sex determination, which may significantly contribute to conservation initiatives.

Methods

We used 12 three-month aquarium reared C. japonicum colony fragments, conducted histological analysis for maturity and sex verification, and performed transcriptome analysis via de novo assembly and mapping using the C. rubrum transcriptome to explore gene expression differences between female and male C. japonicum.

Results

Our histological observations enabled sex identification in 33% of incompletely mature samples. However, the sex of the remaining 67% of samples, classified as immature, could not be identified. RNA-seq yielded approximately 21-31 million short reads from 12 samples. De novo assembly yielded 404,439 highly expressed transcripts. Among them, 855 showed significant differential expression, with 786 differentially expressed transcripts between females and males. Heatmap analysis highlighted 283 female-specific and 525 male-specific upregulated transcripts. Transcriptome assembly mapped to C. rubrum yielded 28,092 contigs, leading to the identification of 190 highly differentially expressed genes, with 113 upregulated exclusively in females and 70 upregulated exclusively in males. Blastp analysis provided putative protein annotations for 83 female and 72 male transcripts. Annotation analysis revealed that female biological processes were related to oocyte proliferation and reproduction, whereas those in males were associated with cell adhesion.

Discussion

Transcriptome analysis revealed sex-specific gene upregulation in incompletely mature C. japonicum and shared transcripts with C. rubrum, providing insight into its gene expression patterns. This study highlights the importance of using both de novo and reference-based assembly methods. Functional enrichment analysis showed that females exhibited enrichment in cell proliferation and reproduction pathways, while males exhibited enrichment in cell adhesion pathways. To the best of our knowledge, this is the first report on the gene expressions of each sex during the spawning season. Our findings offer valuable insights into the physiological ecology of incompletely mature red Japanese precious corals and suggest a method for identifying sex using various genes expressed in female and male individuals. In the future, techniques such as transplantation, artificial fertilization, and larval rearing may involve sex determination methods based on differences in gene expression to help conserve precious coral resources and ecosystems.

The Shot CH1 domain recognises a distinct form of F-actin during Drosophila oocyte determination

In Drosophila, only one cell in a multicellular female germline cyst is specified as an oocyte and a similar process occurs in mammals. The symmetry-breaking cue for oocyte selection is provided by the fusome, a tubular structure connecting all cells in the cyst. The Drosophila spectraplakin Shot localises to the fusome and translates its asymmetry into a polarised microtubule network that is essential for oocyte specification, but how Shot recognises the fusome is unclear. Here, we demonstrate that the actin-binding domain (ABD) of Shot is necessary and sufficient to localise Shot to the fusome and mediates Shot function in oocyte specification together with the microtubule-binding domains. The calponin homology domain 1 of the Shot ABD recognises fusomal F-actin and requires calponin homology domain 2 to distinguish it from other forms of F-actin in the cyst. By contrast, the ABDs of utrophin, Fimbrin, Filamin, Lifeact and F-tractin do not recognise fusomal F-actin. We therefore propose that Shot propagates fusome asymmetry by recognising a specific conformational state of F-actin on the fusome.

MAX controls meiotic entry in sexually undifferentiated germ cells

Meiosis is a specialized type of cell division that occurs physiologically only in germ cells. We previously demonstrated that MYC-associated factor X (MAX) blocks the ectopic onset of meiosis in embryonic and germline stem cells in culture systems. Here, we investigated the Max gene's role in mouse primordial germ cells. Although Max is generally ubiquitously expressed, we revealed that sexually undifferentiated male and female germ cells had abundant MAX protein because of their higher Max gene expression than somatic cells. Moreover, our data revealed that this high MAX protein level in female germ cells declined significantly around physiological meiotic onset. Max disruption in sexually undifferentiated germ cells led to ectopic and precocious expression of meiosis-related genes, including Meiosin, the gatekeeper of meiotic onset, in both male and female germ cells. However, Max-null male and female germ cells did not complete the entire meiotic process, but stalled during its early stages and were eventually eliminated by apoptosis. Additionally, our meta-analyses identified a regulatory region that supports the high Max expression in sexually undifferentiated male and female germ cells. These results indicate the strong connection between the Max gene and physiological onset of meiosis in vivo through dynamic alteration of its expression.

The role of serum-glucocorticoid regulated kinase 1 in reproductive viability: implications from prenatal programming and senescence

OBJECTIVE

Organisms and cellular viability are of paramount importance to living creatures. Disruption of the balance between cell survival and apoptosis results in compromised viability and even carcinogenesis. One molecule involved in keeping this homeostasis is serum-glucocorticoid regulated kinase (SGK) 1. Emerging evidence points to a significant role of SGK1 in cell growth and survival, cell metabolism, reproduction, and life span, particularly in prenatal programming and reproductive senescence by the same token. Whether the hormone inducible SGK1 kinase is a major driver in the pathophysiological processes of prenatal programming and reproductive senescence?

METHOD

The PubMed/Medline, Web of Science, Embase/Ovid, and Elsevier Science Direct literature databases were searched for articles in English focusing on SGK1 published up to July 2023 RESULT: Emerging evidence is accumulating pointing to a pathophysiological role of the ubiquitously expressed SGK1 in the cellular and organismal viability. Under the regulation of specific hormones, extracellular stimuli, and various signals, SGK1 is involved in several biological processes relevant to viability, including cell proliferation and survival, cell migration and differentiation. In line, SGK1 contributes to the development of germ cells, embryos, and fetuses, whereas SGK1 inhibition leads to abnormal gametogenesis, embryo loss, and truncated reproductive lifespan.

CONCLUTION

SGK1 integrates a broad spectrum of effects to maintain the homeostasis of cell survival and apoptosis, conferring viability to multiple cell types as well as both simple and complex organisms, and thus ensuring appropriate prenatal development and reproductive lifespan.

Effects of different hormonal treatments on spermatogenesis advancement in hatchery-produced greater amberjack Seriola dumerili (Risso 1810)

In earlier studies, wild-caught greater amberjack Seriola dumerili (Risso, 1810) males reared in sea cages showed gametogenesis impairment and low sperm production and quality. Here, we (a) examined if F1 hatchery-produced males reared in sea cages also exhibit reproductive dysfunctions and (b) evaluated the effects of gonadotropin releasing hormone agonist (GnRHa) administration through injections (GnRHainj) or sustained-release implants (GnRHaimpl), and human chorionic gonadotropin (hGC) injections on spermatogenesis/spermiation enhancement. Fish were given a hormone treatment just prior to the spawning season, and were transferred to land-based tanks, according to an established spawning induction protocol. Blood samples (n = 6) were obtained on Days 0, 7 and 13 after treatment. Testis samples were obtained on Days 0 (n = 4) and 13 (n = 2 per treatment). The fish prior to their transfer from the sea cages to the land-based tanks, exhibited a low gonadosomatic index, altered sex steroid hormone profile and high density of testicular apoptotic cells. After transfer to tanks, there was a general depression of sex steroid plasma levels parallel to an increase in cortisol concentrations. Despite the negative effect on steroidogenesis by the transfer from the sea, the hormonal treatments increased the number of fish from where sperm could be obtained, as well as testis growth, and reduced testicular apoptosis. Treatment with hCG resulted in the most significant changes in spermatogenesis, while GnRHaimpl appeared to induce less intense, but likely longer-lasting effects. The study indicated that F1 hatchery-produced males also exhibited reproductive dysfunctions as wild-caught captive-reared greater amberjack, and that the observed positive effects of the hormone treatments on spermiation/spermatogenesis were likely mediated by factors other than sex steroid hormones.

Synergistic enhancement of the mouse Pramex1 and Pramel1 in repressing retinoic acid (RA) signaling during gametogenesis

BACKGROUND

PRAME constitutes one of the largest multi-copy gene families in Eutherians, encoding cancer-testis antigens (CTAs) with leucine-rich repeats (LRR) domains, highly expressed in cancer cells and gametogenic germ cells. This study aims to elucidate genetic interactions between two members, Pramex1 and Pramel1, in the mouse Prame family during gametogenesis using a gene knockout approach.

RESULT

Single-gene knockout (sKO) of either Pramex1 or Pramel1 resulted in approximately 7% of abnormal seminiferous tubules, characterized by a Sertoli-cell only (SCO) phenotype, impacting sperm count and fecundity significantly. Remarkably, sKO female mice displayed normal reproductive functions. In contrast, Pramex1/Pramel1 double knockout (dKO) mice exhibited reduced fecundity in both sexes. In dKO females, ovarian primary follicle count decreased by 50% compared to sKO and WT mice, correlating with a 50% fecundity decrease. This suggested compensatory roles during oogenesis in Pramex1 or Pramel1 sKO females. Conversely, dKO males showed an 18% frequency of SCO tubules, increased apoptotic germ cells, and decreased undifferentiated spermatogonia compared to sKO and WT testes. Western blot analysis with PRAMEX1- or PRAMEL1-specific antibodies on sKO testes revealed compensatory upregulation of each protein (30-50%) in response to the other gene's deletion. Double KO males exhibited more severe defects in sperm count and litter size, surpassing Pramex1 and Pramel1 sKO accumulative effects, indicating a synergistic enhancement interaction during spermatogenesis. Additional experiments administering trans-retinoic acid (RA) and its inhibitor (WIN18,446) in sKO, dKO, and WT mice suggested that PRAMEX1 and PRAMEL1 synergistically repress the RA signaling pathway during spermatogenesis.

CONCLUSION

Data from sKO and dKO mice unveil a synergistic interaction via the RA signaling pathway between Pramex1 and Pramel1 genes during gametogenesis. This discovery sets the stage for investigating interactions among other members within the Prame family, advancing our understanding of multi-copy gene families involved in germ cell formation and function.

Endocrine regulation of reproductive biology in echinoderms: An evolutionary perspective from closest marine invertebrate relatives to chordates

Echinoderms are a phylum of invertebrate deuterostomes, which contain echinoids, asteroids, holothuroids, crinoids, and ophiuroids. Echinoderms have special evolutionary position and unique characteristics, including pentamerous radial body structure, elaborate calcareous endoskeletons, and versatile water vascular system. Echinoderms exhibit extraordinarily diverse reproductive modes: asexual reproduction, sexual reproduction, sexual reversal, etc. Endocrine regulation plays important well-known roles in sex differentiation, gonadal development and maturation, gametogenesis, and reproductive behavior in vertebrates. However, the entire picture of reproductive endocrinology in echinoderms as an evolutionary model of the closest marine invertebrate relatives to chordates has not been revealed. Here, we reviewed previous and recent research progress on reproductive endocrinology in echinoderms, mainly including two sections: Sex steroids in echinoderms and neuropeptide regulation in echinoderm reproduction. This review introduces a variety of endocrine regulatory mechanisms in reproductive biology of echinoderms. It discusses the vertebrate-like sex steroids, putative steroidogenic pathway and metabolism, and reproduction-related neuropeptides. The review will provide a deeper understanding about endocrine regulatory mechanisms of gonadal development in lower deuterostomes and the application of endocrine control in economic echinoderm species in aquaculture.

Size-dependent and sex-specific negative effects of micro- and nano-sized polystyrene particles in the terrestrial invertebrate model Drosophila melanogaster

Microplastic pollution is believed to be one of the most widespread and long-lasting changes on a global scale. Our understanding that microplastics significantly impact terrestrial systems and are a global change stressor continues to grow. In the present study, we investigated the negative effect of long-term (28 days of exposure in food) polystyrene particles of micro (1.0-1.9 µm, 0.4-0.6 µm) and nano (0.04-0.06 µm) scale, in low doses, on the fruit fly - representing a common, globally distributed terrestrial invertebrate, and a model species in many fields. Our observations involved such parameters as ingestion and transfer of particles, survival, reproduction, changes in ultrastructure and tissue and cell responses in midgut epithelium (the place of direct contact with plastic), ovary, and testis in adults, and transgenerational effects in larvae. These observations may indicate possible toxic effects of the tested substances, even in low doses, that can be expected in other taxa, in terrestrial ecosystems. We observed a negative impact of polystyrene particles on the fruit fly survival, midgut, ovary, and testis, involving ultrastructural alterations, such as autophagy and/or ultimately necrosis in the midgut, triggering oxidative stress and activating processes of antioxidative protection. Despite the changes, midgut function and reproduction were not altered - spermatogenesis and oogenesis proceeded normally. The effect was size-dependent - the smaller the polystyrene particles were, the more substantial was the impact they caused. Ultrastructural changes and studied parameters, i.e., generation of ROS (overproduction of which generates oxidative stress), total glutathione concentration (involved in defense against ROS, acting in distinct pathways), and total antioxidant concentration (the oxidative defense system) showed the highest levels after exposure to the smallest nanoparticles, and vice versa. The effect was also sex-dependent, with male flies being more sensitive. Negative effects in males were more substantial and more prominent, even after contact with larger particles, compared to females. The smaller particles (0.4-0.6 µm, 0.04-0.06 µm) were transferred to the ovary and accumulated in the oocytes. In this case, a transgenerational negative effect was detected in larvae. It was characterized by size-dependent alterations, with smaller particles triggering higher levels of ROS and cellular oxidative response. Only the largest particles (1.0-1.9 µm) did not pass into the gonad and did not alter the larvae. These observations together demonstrated that polystyrene particles of micro- and nanoscale, even in a low dose, can induce numerous negative effects on terrestrial invertebrates.

Production of sterile mono-sex triploid yellow drum (Nibea albiflora): genotypic females and sex-reversed phenotypic males with emphasis on utilization as surrogate broodstock

Production of sterile mono-sex fish is of great significance for sustainable aquaculture as well as germ cell transplantation. In this study, we aimed to produce mono-sex triploid yellow drum, including genotypic females (XXX female) and sex-reversed phenotypic males (XXX male). Firstly, the mono-female triploids were produced through cold-shock treatment on eggs fertilized with sperm from neo-males. Then, the mono-male triploids were produced by the sex reversal of mono-female triploids with oral administration of letrozole (LZ). We comparatively investigated the growth and gonadal development in the mono-sex triploids. The results showed that the triploids displayed similar growth performance to their diploids throughout their first year, but had impaired gonadosomatic index and gametogenesis. No mature gametes were produced in the triploids during their first spawning season. Meanwhile, we analyzed the process of gametogenesis in the both sex of triploids. Ultrastructure of gametogenesis showed that the germ cells arrested at abnormal metaphase 1 in females, while males had irregular meiotic divisions, variable-sized spermatid and degenerated cells. The expression levels of meiosis-related genes (i.e., sycp3 and rec8) confirmed the abnormal meiosis in the triploids. Furthermore, the gonadal development was also determined by the expression patterns of vasa, dmrt1 and cyp19a1a. Abnormal expression of vasa mRNA and protein were detected in triploids. High cyp19a1a expression levels suggested the sex steroid hormones production might be at least partially functional in triploid females. In addition, high dmrt1 expression levels confirmed the masculinization and testicular development of sex-reversed triploid males by LZ. Our findings provide an efficient protocol to produce sterile mono-sex triploid yellow drum and provide new insights into the mechanism of gonadal sterility of triploid fish.

Whole-Genome Re-sequencing and Transcriptome Reveal Candidate Genes and Pathways Associated with Hybrid Sterility in Hermaphroditic Argopecten Scallops

The interspecific hybrid scallops generated from the hermaphroditic bay scallops (Argopecten irradians) and Peruvian scallops (Argopecten purpuratus) showed significant heterosis in growth. However, its sterility limits large-scale hybridization and hinders the development of the scallop breeding industry. Hybrid sterility is regulated by plenty of genes and involves a range of biochemical and physiological transformations. In this study, whole-genome re-sequencing and transcriptomic analysis were performed in sterile and fertile hybrid scallops. The potential genetic variations and abnormally expressed genes were detected to explore the mechanism underlying hybrid sterility in hermaphroditic Argopecten scallops. Compared with fertile hybrids, 24 differentially expressed genes (DEGs) with 246 variations were identified to be related to fertility regulation, which were mainly enriched in germarium-derived egg chamber formation, spermatogenesis, spermatid development, mismatch repair, mitotic and meiotic cell cycles, Wnt signaling pathway, MAPK signaling pathway, calcium modulating pathway, and notch signaling pathway. Specifically, variation and abnormal expression of these genes might inhibit the progress of mitosis and meiosis, promote cell apoptosis, and impede the genesis and maturation of gametes in sterile hybrid scallops. Eleven DEGs (XIAP, KAZN, CDC42, MEIS1, SETD1B, NOTCH2, TRPV5, M- EXO1, GGT1, SBDS, and TBCEL) were confirmed by qRT-PCR validation. Our findings may enrich the determination mechanism of hybrid sterility and provide new insights into the use of interspecific hybrids for extensive breeding.

Why we need stem-cell derived gametes

In-vitro gametogenesis (IVG) is almost exclusively discussed as a potential solution for people who have no (functional) gametes. However, IVG could also be seen as an alternative to standard IVF. Instead of submitting women to ovarian stimulation and invasive oocyte retrieval, the creation of oocytes from stem cells should be the first treatment option (assuming it to be reasonably safe and effective). The primary reason for the application of this method would not be for these women to become genetic parents but to alleviate the physical and psychological burden of standard IVF treatment on them.

Histopathological changes in the greenshell mussel, Perna canaliculus, in response to chronic thermal stress

Climate change associated temperature challenges pose a serious threat to the marine environment. Elevations in average sea surface temperatures are occurring and increasing frequency of marine heatwaves resulting in mortalities of organisms are being reported. In recent years, marine farmers have reported summer mass mortality events of the New Zealand Greenshell mussel, Perna canaliculus, during the summer months; however, the etiological agents have yet to be determined. To elucidate the role of thermal stress, adult P. canaliculus were exposed to three chronic temperature treatments: a benign control of 17 °C and stressful elevations of 21 °C and 24 °C. Eight mussels per treatment were collected each month throughout a 14-month challenge period to identify and investigate histopathological differences among P. canaliculus populations exposed to the three temperatures. Histopathology revealed several significant deleterious alterations to tissues associated with temperature and exposure time. Increasing temperature and progression of time resulted in 1) an increase in the number of focal lipofuscin-ceroid aggregations, 2) an increase in focal hemocytosis, 3) an increase in the thickness of the sub-epithelial layer of the intestinal tract and 4) a decreased energy reserve cell (glycogen) coverage in the mantle. Prolonged exposure, irrespective of temperature, impacted gametogenesis, which was effectively arrested. Furthermore, increased levels of the heat shock protein 70 kDa (HSP 70) were seen in gill and gonad from thermally challenged mussels. The occurrence of the parasite Perkinsus olseni at month 5 in the 24 °C treatment, and month 7 at 21 °C was unexpected and may have exacerbated the fore-mentioned tissue conditions. Prolonged exposure to stable thermal conditions therefore appears to impact P. canaliculus, tissues with implications for broodstock captivity. Mussels experiencing elevated, temperatures of 21 and 24 °C demonstrated more rapid pathological signs. This research provides further insight into the complex host-pathogen-environment interactions for P. canaliculus in response to prolonged elevated temperature.

Ovary organization and ultrastructure in six species of Amynthas and Metaphire earthworms (Annelida, Crassiclitellata, Megascolecidae)

Ovaries in earthworms belonging to the family Megascolecidae are paired structures attached to the septum in the anterior part of the XIII segment. They are fan to rosette shaped with numerous rows of growing oocytes, known as egg strings, radiating from the ovary center towards the segmental cavity. The histological and ultrastructural ovary organization in megascolecids and the course of oogenesis remain unknown. The paper presents the results of light and electron microscopy analyses of ovaries in six megascolecid species, three from the genus Amynthas and three from Metaphire. Both parthenogenetic and sexually reproducing species were included in the study. The organization and ultrastructure of ovaries in all studied species are broadly similar. Considering the histological organization of ovaries, they could be divided into two zones. Zone I (proximal, close to the connection with the septum) is tightly packed with germline and somatic cells. Germ cells are interconnected via intercellular bridges and thin strands of the central cytoplasm (known as cytophore) and form syncytial cysts. Cysts unite oogonia, early meiotic cells (till diplotene), and clustering cells develop synchronously. During diplotene, interconnected cells lose developmental synchrony; most probably, one cell per cyst grows faster than others, detaches from the cysts, and becomes an oocyte. The remaining cells grow slightly and are still interconnected via the thin and reticular cytophore; these cells are considered nurse cells. Zone II has a form of egg strings where growing oocytes are isolated one from another by thin somatic cells and form short cords. We present the ultrastructural details of germline and somatic cells. We propose the term "Amynthas" type of ovaries for this ovary organization. We suppose that such ovaries are characteristic of other megascolecids and related families.

Multipotent fetal stem cells in reproductive biology research

Due to the limited accessibility of the in vivo situation, the scarcity of the human tissue, legal constraints, and ethical considerations, the underlying molecular mechanisms of disorders, such as preeclampsia, the pathological consequences of fetomaternal microchimerism, or infertility, are still not fully understood. And although substantial progress has already been made, the therapeutic strategies for reproductive system diseases are still facing limitations. In the recent years, it became more and more evident that stem cells are powerful tools for basic research in human reproduction and stem cell-based approaches moved into the center of endeavors to establish new clinical concepts. Multipotent fetal stem cells derived from the amniotic fluid, amniotic membrane, chorion leave, Wharton´s jelly, or placenta came to the fore because they are easy to acquire, are not associated with ethical concerns or covered by strict legal restrictions, and can be banked for autologous utilization later in life. Compared to adult stem cells, they exhibit a significantly higher differentiation potential and are much easier to propagate in vitro. Compared to pluripotent stem cells, they harbor less mutations, are not tumorigenic, and exhibit low immunogenicity. Studies on multipotent fetal stem cells can be invaluable to gain knowledge on the development of dysfunctional fetal cell types, to characterize the fetal stem cells migrating into the body of a pregnant woman in the context of fetomaternal microchimerism, and to obtain a more comprehensive picture of germ cell development in the course of in vitro differentiation experiments. The in vivo transplantation of fetal stem cells or their paracrine factors can mediate therapeutic effects in preeclampsia and can restore reproductive organ functions. Together with the use of fetal stem cell-derived gametes, such strategies could once help individuals, who do not develop functional gametes, to conceive genetically related children. Although there is still a long way to go, these developments regarding the usage of multipotent fetal stem cells in the clinic should continuously be accompanied by a wide and detailed ethical discussion.

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.

Review: A barnyard in the lab: prospect of generating animal germ cells for breeding and conservation

In vitro gametogenesis (IVG) offers broad opportunities for gaining detailed new mechanistic knowledge of germ cell biology that will enable progress in the understanding of human infertility, as well as for applications in the conservation of endangered species and for accelerating genetic selection of livestock. The realisation of this potential depends on overcoming key technical challenges and of gaining more detailed knowledge of the ontogeny and developmental programme in different species. Important differences in the molecular mechanisms of germ cell determination and epigenetic reprogramming between mice and other animals have been elucidated in recent years. These must be carefully considered when developing IVG protocols, as cellular kinetics in mice may not accurately reflect mechanisms in other mammals. Similarly, diverse stem cell models with potential for germ cell differentiation may reflect alternative routes to successful IVG. In conclusion, the fidelity of the developmental programme recapitulated during IVG must be assessed against reference information from each species to ensure the production of healthy animals using these methods, as well as for developing genuine models of gametogenesis.

Exposure of ambient PM2.5 during gametogenesis period affects the birth outcome: Results from the project ELEFANT

Various environmental and behavioural factors influence neonatal health. Gamete formation (gametogenesis) is a crucial period which affects embryo development and neonatal health and ambient air pollution exposure at this stage may lead to an adverse birth outcome. Previous epidemiological and toxicological research demonstrated a strong association between maternal ambient air pollution exposure and adverse birth outcomes. However, the joint exposure-outcome of paternal exposure (76 days before the last menstruation and 14 days after the last menstruation) and maternal exposure (14 days after the last menstruation) when exploring the mechanism of the influence of air pollutants on pregnancy outcome and neonatal health remains unexplored. Here, in the Project Environmental and LifEstyle FActors iN metabolic health throughout life-course Trajectories (ELEFANT), we collected the data of 10,960 singleton pregnant women with 24-42 completed gestational weeks and included them in this study. A multinominal logistic regression model was applied to investigate the association between adverse birth outcomes and ambient PM_2.5 exposure levels during spermatogenesis and oogenesis. Results from the binary classification of ambient PM_2.5 exposure showed that the risk of abnormal birthweight was significantly greater when ambient PM_2.5 exposure was both higher during spermatogenesis and oogenesis, with RRs of 1.86 (95% CI: 1.02, 3.39). The risk of macrosomia (RR: 1.88 (95% CI: 1.13, 3.12)) increased significantly when ambient PM_2.5 levels were higher during spermatogenesis. Primiparity and primigravity are more likely to be influenced by higher ambient PM_2.5 levels during spermatogenesis. In conclusion, more attention should be paid to higher exposure level of ambient PM_2.5 during spermatogenesis.

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.

Survival and growth of triploid eastern oysters, Crassostrea virginica, produced from wild diploids collected from low-salinity areas

Triploid Eastern oysters have been reported to suffer greater mortalities than diploids when exposed to low-salinity (<5) conditions in the U.S. Gulf of Mexico and Atlantic estuaries. As such, the effect of broodstock parentage was investigated on the low-salinity tolerance of triploid progeny produced by mating diploid females (collected from three Louisiana estuaries differing in salinity regimes) with male tetraploids at two hatcheries. Diploid crosses were also produced using the wild broodstocks to verify expected differences in low-salinity tolerance among diploid progeny and between ploidy levels. All progeny were deployed at low and moderate-salinity (averages of 9.3 and 19.4) field sites to monitor monthly growth and mortality. Sex ratio, gametogenic stage, gonad-to-body ratio, condition index, and Perkinsus marinus infection were also measured periodically at both field sites Although high triploid mortality at the low-salinity site prevented complete analysis, results indicated that diploid parentage had little effect on triploid survival at low salinity. Broodstock parentage affected diploid mortality and growth, although results did not match with predictions made based on historical salinity at broodstock collection sites. Ploidy level had the largest effect on triploid survival and growth followed by the hatchery site where the oysters were produced.

Dissection, Fixation, and Standard Staining of Adult Drosophila Ovaries

Studies of the Drosophila ovary have provided significant insight into the molecular and cellular processes that control cell function, tissue organization, and animal development. To characterize mutants with defects in oogenesis or to observe the distribution of gene products involved in egg production, the ovaries must be carefully extracted and prepared for analysis. This chapter describes the manual dissection of ovaries from adult Drosophila females, followed by standard fixation and staining of the isolated tissue. Specifically, this chapter provides procedures for simple DNA and F-actin staining to assess cell and tissue morphology, as well as immunostaining to localize proteins of interest.

Comparative reproductive biology of two sympatric Hypostomus in a Neotropical river

Congeneric species often coexist in sympatry using behavioral and morphological adaptations to reduce competition and interspecific interference, but reproductive patterns behind coexistence remain unknown. We analyzed the gonadal morphology and development, reproductive cycle, and population structure of two sympatric congeneric fishes to evaluate the degree of overlap and differentiation of the reproductive biology between species in a Neotropical river. Development of testes and ovaries were similar between species, both showing asynchronous gonadal development, large diameter of gametes and synthesis of mucosubstances by follicle cells to form adhesive eggs. Although the morphometry of germ cells did not present differences, the zona radiata of mature eggs in Hypostomus garmani was markedly thicker than H. francisci, which suggests different spawning habitats. Both species have greater reproductive activity in the rainy season, concomitant with increase in water temperature, however H. garmani initiates and ends its reproduction earlier than H. francisci, indicating a differentiation of reproductive periods. Sexually mature males and females of H. francisci reproduced at a larger mean size then H. garmani. The two congeneric species had a similar abundance and sex ratios in the study area. Results show that although the species exhibited broad overlap of reproductive traits, a spatial and temporal differentiation of the reproductive biology was present. This study contributes to understanding reproductive mechanisms that may facilitate coexistence between congeneric sympatric species.

A novel class of sulphonamides potently block malaria transmission by targeting a Plasmodium vacuole membrane protein

Phenotypic cell-based screens are critical tools for discovering candidate drugs for development, yet identification of the cellular target and mode of action of a candidate drug is often lacking. Using an imaging-based screen, we recently discovered an N-[(4-hydroxychroman-4-yl)methyl]-sulphonamide (N-4HCS) compound, DDD01035881, that blocks male gamete formation in the malaria parasite life cycle and subsequent transmission of the parasite to the mosquito with nanomolar activity. To identify the target(s) of DDD01035881, and of the N-4HCS class of compounds more broadly, we synthesised a photoactivatable derivative, probe 2. Photoaffinity labelling of probe 2 coupled with mass spectrometry identified the 16 kDa Plasmodium falciparum parasitophorous vacuole membrane protein Pfs16 as a potential parasite target. Complementary methods including cellular thermal shift assays confirmed that the parent molecule DDD01035881 stabilised Pfs16 in lysates from activated mature gametocytes. Combined with high-resolution, fluorescence and electron microscopy data, which demonstrated that parasites inhibited with N-4HCS compounds phenocopy the targeted deletion of Pfs16 in gametocytes, these data implicate Pfs16 as a likely target of DDD01035881. This finding establishes N-4HCS compounds as being flexible and effective starting candidates from which transmission-blocking antimalarials can be developed in the future.

Molecular characterization of Vasa homolog in the pen shell Atrina pectinata: cDNA cloning and expression analysis during gonadal development

Vasa is an ATP-dependent RNA helicase of the DEAD (Asp-Glu-Ala-Asp) box family and a representative component of the germ plasm. In this study, we cloned the full-length vasa homolog in the bivalve Atrina pectinata (psvasa), and performed phylogenetic analysis, mRNA expression analysis for tissue-specific distributions, and immunostaining analysis to reveal its histological localization. The sequence of psvasa was 3587 bp in length and contained a 5' untranslated region of 150 bp, an open reading frame of 2214 bp, and a 3' untranslated region of 1223 bp. The deduced amino acid sequence of psvasa was 737 amino acids long and contained evolutionarily conserved sequences reported in other animals. The mRNA expression analysis showed the highest expression levels in the gonads. Expression was especially high in the ovaries, followed by the testes. The immunostaining analysis showed Vasa-positive cells in the developing gonads, suggesting the presence of putative germ stem cells contributing to the supply of germ cells. Furthermore, characteristic Vasa signals were observed in the basophilic nuclei of the oocytes, suggesting that psvasa plays an important role in the progression of meiosis in oocytes.

Rattus norvegicus Spermatogenesis Colony-Forming Assays

Knowledge gaps persist on signaling pathways and metabolic states in germ cells sufficient to support spermatogenesis independent of a somatic environment. Consequently, methods to culture mammalian stem cells through spermatogenesis in defined systems have not been established. Lack of success at culturing mammalian stem cells through spermatogenesis in defined systems reflects an inability to experimentally recapitulate biochemical events that develop in germ cells within the testis-specific seminiferous epithelium. Complex germ and somatic cell associations that develop each seminiferous epithelial cycle support such a hypothesis, conceivably explaining why highly pure mammalian spermatogonia do not effectively develop into and through meiosis without somatic cells. Here, we outline an in vitro spermatogenesis colony-forming assay to study how differentiating spermatogonial syncytia develop from rat spermatogonial stem cell lines. Robust spermatogonial differentiation under defined culture conditions, once established, is anticipated to facilitate molecular biology studies on pre-meiotic steps in gametogenesis by providing soma-free bioassays to systematically identify spermatogenic factors that promote meiotic progression in vitro.

Endocrine disruption and reproductive impairment of methylparaben in adult zebrafish

Methylparaben (MeP) is one of the most frequently used preservatives in our daily products. However, it is becoming an aquatic pollutant of emerging concern. To reveal the endocrine disruption mechanism and reproductive impairment of MeP, the present study exposed adult zebrafish to 0, 1, 3, and 10 μg/L (0, 6.6, 19.7, and 65.7 nM) of MeP for 28 days. The results showed that subchronic exposure to 10 μg/L of MeP significantly increased the gonadosomatic index in zebrafish. Spermatogenesis and oogenesis were blocked by MeP at concentrations as low as 1 μg/L. Furthermore, parental exposure to MeP induced developmental deficits in offspring larvae, by increasing mortality, stimulating precocious hatching, and elevating heart rate. Blood concentrations of estradiol, testosterone, and 11-keto-testosterone were consistently lowered in MeP exposure groups. Transcriptional results evidenced that the disturbance in steroidogenesis and feedback regulation mechanisms along the hypothalamic-pituitary-gonadal axis underlay the imbalance of sex hormones. In line with the low estradiol level, hepatic production of vitellogenin (VTG) was significantly down-regulated, subsequently leading to a deficiency of VTG supply during oogenesis. To our knowledge, this is the first study to provide systemic insight about the antiestrogenic activity and reproductive toxicity of MeP.

Dynamic transcriptome analysis reveals the gene network of gonadal development from the early history life stages in dwarf surfclam Mulinia lateralis

BACKGROUND

Gonadal development is driven by a complex genetic cascade in vertebrates. However, related information remains limited in molluscs owing to the long generation time and the difficulty in maintaining whole life cycle in the lab. The dwarf surfclam Mulinia lateralis is considered an ideal bivalve model due to the short generation time and ease to breed in the lab.

RESULTS

To gain a comprehensive understanding of gonadal development in M. lateralis, we conducted a combined morphological and molecular analysis on the gonads of 30 to 60 dpf. Morphological analysis showed that gonad formation and sex differentiation occur at 35 and 40-45 dpf, respectively; then the gonads go through gametogenic cycle. Gene co-expression network analysis on 40 transcriptomes of 35-60 dpf gonads identifies seven gonadal development-related modules, including two gonad-forming modules (M6, M7), three sex-specific modules (M14, M12, M11), and two sexually shared modules (M15, M13). The modules participate in different biological processes, such as cell communication, glycan biosynthesis, cell cycle, and ribosome biogenesis. Several hub transcription factors including SOX2, FOXZ, HSFY, FOXL2 and HES1 are identified. The expression of top hub genes from sex-specific modules suggests molecular sex differentiation (35 dpf) occurs earlier than morphological sex differentiation (40-45 dpf).

CONCLUSION

This study provides a deep insight into the molecular basis of gonad formation, sex differentiation and gametogenesis in M. lateralis, which will contribute to a comprehensive understanding of the reproductive regulation network in molluscs.

Epigenetics in the etiology and management of infertility

BACKGROUND

Epigenetic disruptions have been implicated in some cases of infertility and can serve as therapeutic targets. However, the involvement of epigenetics in infertility has not received adequate attention.

AIM

This study aimed to determine the epigenetic basis of infertility in order to enhance public knowledge.

METHODS

Relevant articles on the subject were collected from PubMed, RCA, Google Scholar, SpringerLink, and Scopus. The articles were pooled together and duplicates were removed using Endnote software.

RESULTS

Available information shows that epigenetic mechanisms, mainly DNA methylation, histone modification, and microRNA interference are necessary for normal gametogenesis and embryogenesis. As a result, epigenetic disruptions in genes that control gametogenesis and embryogenesis, such as DDX3X, ADH4, AZF, PLAG1, D1RAS3, CYGB, MEST, JMJD1A, KCNQ1, IGF2, H19, and MTHFR may result in infertility. Aberrant DNA methylation during genomic imprinting and parental epigenetic mark erasures, in particular, may affect the DNA epigenomes of sperm and oocytes, resulting in reproductive abnormalities. Histone epigenetic dysregulation during oocyte development and histone-protamine replacement in the sperm may also cause reproductive abnormalities. Furthermore, overexpression or repression of certain microRNAs embedded in the ovary, testis, embryo, as well as granulosa cells and oocytes may impair reproduction. Male infertility is characterized by spermatogenesis failure, which includes oligozoospermia, asthenozoospermia, and teratozoospermia, while female infertility is characterized by polycystic ovary syndrome. Some epigenetic modifications can be reversed by deactivating the regulatory enzymes, implying that epigenetic reprogramming could help treat infertility in some cases. For some disorders, epigenetic drugs are available, but none have been formulated for infertility.

CONCLUSION

Some cases of infertility have an epigenetic etiology and can be treated by reversing the same epigenetic mechanism that caused it. As a result, medical practitioners are urged to come up with epigenetic treatments for infertility that have an epigenetic cause.

Epigenetic dynamics during sexual reproduction: At the nexus of developmental control and genomic integrity

Epigenetic marks influence gene regulation and genomic stability via the repression of transposable elements. During sexual reproduction, tight regulation of the epigenome must take place to maintain the repression of transposable elements while still allowing changes in cell-specific transcriptional programs. In plants, epigenetic marks are reorganized during reproduction and a reinforcing mechanism takes place to ensure transposable elements silencing. In this review, we describe the latest advances in characterizing the cell-specific epigenetic changes occurring from sporogenesis to seed development, with a focus on DNA methylation. We highlight the epigenetic co-regulation between transposable elements and developmental genes at different stages of plant reproduction.

Exposure to difenoconazole induces reproductive toxicity in zebrafish by interfering with gamete maturation and reproductive behavior

Difenoconazole (DCZ) is a triazole fungicide that negatively affects aquatic organisms and humans. However, data regarding the reproductive toxicity of DCZ are insufficient. In this study, we used zebrafish (from 2 h post-fertilization [hpf] to adulthood) as a model to evaluate whether DCZ at environmentally relevant concentrations (0.1, 1.0, and 10.0 μg/L) induces reproductive toxicity. After exposure to DCZ, egg production and fertilization rates were reduced by 1.0 and 10.0 μg/L. A significant decrease in gamete frequency (late vitellogenic oocytes and spermatozoa) was observed at 10.0 μg/L. The concentrations of 17β-estradiol (E2), testosterone (T), and vitellogenin (VTG) were disrupted in females and males by 1.0 and 10.0 μg/L. Exposure to 10.0 μg/L DCZ significantly inhibited the contact time between female and male fish, which was mainly achieved by affecting male fish. The transcription of genes involved in the hypothalamus-pituitary-gonad (HPG) axis was significantly changed after treatment with DCZ. Overall, these data show that the endocrine-disrupting effect of DCZ on the zebrafish HPG axis inhibited gamete maturation and disrupted reproductive behavior, reducing fertility.

The high diversity of gametogenic pathways in amphispermic water frog hybrids from Eastern Ukraine

Interspecific hybridization can disrupt canonical gametogenic pathways, leading to the emergence of clonal and hemiclonal organisms. Such gametogenic alterations usually include genome endoreplication and/or premeiotic elimination of one of the parental genomes. The hybrid frog Pelophylax esculentus exploits genome endoreplication and genome elimination to produce haploid gametes with chromosomes of only one parental species. To reproduce, hybrids coexist with one of the parental species and form specific population systems. Here, we investigated the mechanism of spermatogenesis in diploid P. esculentus from sympatric populations of P. ridibundus using fluorescent in situ hybridization. We found that the genome composition and ploidy of germ cells, meiotic cells, and spermatids vary among P. esculentus individuals. The spermatogenic patterns observed in various hybrid males suggest the occurrence of at least six diverse germ cell populations, each with a specific premeiotic genome elimination and endoreplication pathway. Besides co-occurring aberrant cells detected during meiosis and gamete aneuploidy, alterations in genome duplication and endoreplication have led to either haploid or diploid sperm production. Diploid P. esculentus males from mixed populations of P. ridibundus rarely follow classical hybridogenesis. Instead, hybrid males simultaneously produce gametes with different genome compositions and ploidy levels. The persistence of the studied mixed populations highly relies on gametes containing a genome of the other parental species, P. lessonae.

RWP-RK domain-containing transcription factors in the Viridiplantae: biology and phylogenetic relationships

The RWP-RK protein family is a group of transcription factors containing the RWP-RK DNA-binding domain. This domain is an ancient motif that emerged before the establishment of the Viridiplantae-the green plants, consisting of green algae and land plants. The domain is mostly absent in other kingdoms but widely distributed in Viridiplantae. In green algae, a liverwort, and several angiosperms, RWP-RK proteins play essential roles in nitrogen responses and sexual reproduction-associated processes, which are seemingly unrelated phenomena but possibly interdependent in autotrophs. Consistent with related but diversified roles of the RWP-RK proteins in these organisms, the RWP-RK protein family appears to have expanded intensively, but independently, in the algal and land plant lineages. Thus, bryophyte RWP-RK proteins occupy a unique position in the evolutionary process of establishing the RWP-RK protein family. In this review, we summarize current knowledge of the RWP-RK protein family in the Viridiplantae, and discuss the significance of bryophyte RWP-RK proteins in clarifying the relationship between diversification in the RWP-RK protein family and procurement of sophisticated mechanisms for adaptation to the terrestrial environment.

The foundational framework of tumors: Gametogenesis, p53, and cancer

The completion-of-tumor hypothesis involved in the dynamic interplay between the initiating oncogenic event and progression is essential to better recognize the foundational framework of tumors. Here we review and extend the gametogenesis-related hypothesis of tumors, because high embryonic/germ cell traits are common in tumors. The century-old gametogenesis-related hypothesis of tumors postulated that tumors arise from displaced/activated trophoblasts, displaced (lost) germ cells, and the reprogramming/reactivation of gametogenic program in somatic cells. Early primordial germ cells (PGCs), embryonic stem (ES) cells, embryonic germ cells (EGCs), and pre-implantation embryos at the stage from two-cell stage to blastocysts originating from fertilization or parthenogenesis have the potential to develop teratomas/teratocarcinomas. In addition, the teratomas/teratocarcinomas/germ cells occur in gonads and extra-gonads. Undoubtedly, the findings provide strong support for the hypothesis. However, it was thought that these tumor types were an exception rather than verification. In fact, there are extensive similarities between somatic tumor types and embryonic/germ cell development, such as antigens, migration, invasion, and immune escape. It was documented that embryonic/germ cell genes play crucial roles in tumor behaviors, e.g. tumor initiation and metastasis. Of note, embryonic/germ cell-like tumor cells at different developmental stages including PGC and oocyte to the early embryo-like stage were identified in diverse tumor types by our group. These embryonic/germ cell-like cancer cells resemble the natural embryonic/germ cells in morphology, gene expression, the capability of teratoma formation, and the ability to undergo the process of oocyte maturation and parthenogenesis. These embryonic/germ cell-like cancer cells are derived from somatic cells and contribute to tumor formation, metastasis, and drug resistance, establishing asexual meiotic embryonic life cycle. p53 inhibits the reactivation of embryonic/germ cell state in somatic cells and oocyte-like cell maturation. Based on earlier and our recent studies, we propose a novel model to complete the gametogenesis-related hypothesis of tumors, which can be applied to certain somatic tumors. That is, tumors tend to establish a somatic asexual meiotic embryonic cycle through the activation of somatic female gametogenesis and parthenogenesis in somatic tumor cells during the tumor progression, thus passing on corresponding embryonic/germ cell traits leading to the malignant behaviors and enhancing the cells' independence. This concept may be instrumental to better understand the nature and evolution of tumors. We rationalize that targeting the key events of somatic pregnancy is likely a better therapeutic strategy for cancer treatment than directly targeting cell mitotic proliferation, especially for those tumors with p53 inactivation.

Discovery of Nanos1 and Nanos2/3 as Germ Cell Markers During Scallop Gonadal Development

Nanos are conserved genes involved in germline cell specification and differentiation. However, little is known about the role of different members of Nanos family in germ cell development in mollusks. In the present study, we conducted genome-wide identification of Nanos family in an economically important scallop Patinopecten yessoensis, and detected their expression in adult tissues and during early development. Two Nanos genes (PyNanos1, PyNanos2/3) were identified, both of which have the N-terminal NOT1-interacting motif and C-terminal (CCHC)₂ zinc finger domain. Expression profiles showed that PyNanos1 and PyNanos2/3 were primarily expressed in the gonads, with PyNanos1 being localized in the oogonia, oocytes, and spermatogonia, while PyNanos2/3 being specifically in spermatogonia. The results suggest that PyNanos are germ cell specific and may play crucial roles in gametogenesis in the scallop. PyNanos1 is a maternal gene, which is distributed uniformly at early cleavage, and restricted to 2-3 cell clusters from blastulae to trochophore larvae, suggesting its potential role in the formation of PGCs. Zygotically expressed PyNanos2/3 displayed a similar signal with PyNanos1 in the trochophore larvae, suggesting it may also participate in the formation and/or maintenance of PGCs. This study will benefit germplasm exploitation and conservation in bivalves, and facilitate a better understanding of the evolution of Nanos family and the role of different Nanos in germ cell development in mollusks.

Past, present and future of Clytia hemisphaerica as a laboratory jellyfish

The hydrozoan species Clytia hemisphaerica was selected in the mid-2000s to address the cellular and molecular basis of body axis specification in a cnidarian, providing a reliable daily source of gametes and building on a rich foundation of experimental embryology. The many practical advantages of this species include genetic uniformity of laboratory jellyfish, derived clonally from easily-propagated polyp colonies. Phylogenetic distance from other laboratory models adds value in providing an evolutionary perspective on many biological questions. Here we outline the current state of the art regarding available experimental approaches and in silico resources, and illustrate the contributions of Clytia to understanding embryo patterning mechanisms, oogenesis and regeneration. Looking forward, the recent establishment of transgenesis methods is now allowing gene function and imaging studies at adult stages, making Clytia particularly attractive for whole organism biology studies across fields and extending its scientific impact far beyond the original question of interest.

Evolutionary dynamics and conserved function of the Tudor domain-containing (TDRD) proteins in teleost fish

Tudor domain-containing (TDRD) proteins, the germline enriched protein family, play essential roles in the process of gametogenesis and genome stability through their interaction with the PIWI-interacting RNA (piRNA) pathway. Several studies have suggested the rapid evolution of the piRNA pathway in teleost lineages with striking reproductive diversity. However, there is still limited information about the function and evolution of Tdrd genes in teleost species. In this study, through genome wide screening, 13 Tdrd family genes were identified in economically important aquaculture fish, including spotted sea bass (Lateolabrax maculatus), Asian sea bass (Lates calcarifer), and tongue sole (Cynoglossus semilaevis). With copy number, structure, phylogeny, and synteny analysis, duplication of Tdrd6 and Tdrd7, as well as loss of Stk31 and Tdrd10, were characterized in teleost lineages. Codon based molecular evolution analysis indicated faster evolution of teleost Tdrd genes than that in mammals, potentially associated with the accelerated evolution of the piRNA pathway in teleost lineages. The evolutionary diversity of Tdrd genes was also detected between different teleost lineages. RNA-seq analysis showed that most teleost Tdrd genes were dominantly expressed in gonads, particularly highly expressed in testis, such as Tdrd6, Tdrd7a, Tdrd9, Ecat8, and Tdrd15. The varied expression and evolutionary pattern between the duplicated Tdrd6 and Tdrd7 in teleosts may indicate their functional diversification. All these results suggest a conserved function of teleost Tdrd family in gametogenesis and the piRNA pathway, which could lay a foundation for the evolution of Tdrd genes and be helpful for further deciphering of Tdrd functions in teleosts.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-021-00118-7.

Transcriptional dynamics of gametogenesis in the green seaweed Ulva mutabilis identifies an RWP-RK transcription factor linked to reproduction

BACKGROUND

The molecular mechanism underlying sexual reproduction in land plants is well understood in model plants and is a target for crop improvement. However, unlike land plants, the genetic basis involved in triggering reproduction and gamete formation remains elusive in most seaweeds, which are increasingly viewed as an alternative source of functional food and feedstock for energy applications.

RESULTS

Gametogenesis of Ulva mutabilis, a model organism for green seaweeds, was studied. We analyzed transcriptome dynamics at different time points during gametogenesis following induction of reproduction by fragmentation and removal of sporulation inhibitors. Analyses demonstrated that 45% of the genes in the genome were differentially expressed during gametogenesis. We identified several transcription factors that potentially play a key role in the early gametogenesis of Ulva given the function of their homologs in higher plants and microalgae. In particular, the detailed expression pattern of an evolutionarily conserved transcription factor containing an RWP-RK domain suggested a key role during Ulva gametogenesis.

CONCLUSIONS

Transcriptomic analyses of gametogenesis in the green seaweed Ulva highlight the importance of a conserved RWP-RK transcription factor in the induction of sexual reproduction. The identification of putative master regulators of gametogenesis provides a starting point for further functional characterization.

Epigenetic transgenerational inheritance, gametogenesis and germline development†

One of the most important developing cell types in any biological system is the gamete (sperm and egg). The transmission of phenotypes and optimally adapted physiology to subsequent generations is in large part controlled by gametogenesis. In contrast to genetics, the environment actively regulates epigenetics to impact the physiology and phenotype of cellular and biological systems. The integration of epigenetics and genetics is critical for all developmental biology systems at the cellular and organism level. The current review is focused on the role of epigenetics during gametogenesis for both the spermatogenesis system in the male and oogenesis system in the female. The developmental stages from the initial primordial germ cell through gametogenesis to the mature sperm and egg are presented. How environmental factors can influence the epigenetics of gametogenesis to impact the epigenetic transgenerational inheritance of phenotypic and physiological change in subsequent generations is reviewed.

Experimental data-sets on sex reversal and histopathological assessment of potential endocrine disrupting effects of graphene oxide on Japanese medaka (Oryzias latipes) larvae at the onset of maturity

The datasets of this article present the experimental parameters resulting from the assessment of sex reversal (SR) as a biomarker of endocrine disrupting effect of graphene oxide (GO), together with the histopathological assessment of ovary, testis, liver and kidneys of medaka larvae. These data sets support the published article "Sex-reversal and histopathological assessment of potential endocrine-disrupting effect of graphene oxide on Japanese medaka (Oryzias larvae) larvae." The experiments were conducted on one day-post hatch (dph) Japanese medaka fries (orange-red variety) exposed to different concentrations of GO (2.5-20 mg/L) by immersion in embryo-rearing medium (ERM) for 96 h under laboratory conditions (25 ± 1 °C; light cycle 16 h light: 8 h dark). No food was given during the GO-exposure period. Controls (no GO) were identically maintained in ERM. After treatment, the larvae were maintained in balanced salt solution (BSS) with feeding and allowed to grow for 6 more weeks in a GO-free environment. On 47 dph, the larvae were anesthetized in MS-222, and the total length (mm) and body weight (mg) were recorded. For histopathological and phenotypic sex assessments, after sacrifice, the body excluding post-anal tail was preserved in 4% paraformaldehyde containing 0.05% Tween 20; ovary, testis, liver and kidneys were evaluated in 5 µm thick sections stained on haematoxylin eosin (HE) following OECD guidelines. The photomicrographs of sections were made using either an Olympus B-max 40 microscope attached to a camera with Q-capture Pro 7 software or an Olympus CKX53 inverted microscope with DP22 camera and CellSens software. A minimum 3 images of gonads in different regions were further analysed by imagej software and used for counting spermatogonia (SPG) and spermatocytes (SPT) in testis as well as perinucleolar (PNO) and cortical alveolar (CAO) oocytes in ovary. Data were expressed as number of SPG or SPT/mm² testis and % CAO or PNO in an ovary. Preserved tail in TRI reagent was used for genomic DNA extraction and the genetic sex was assessed by genotyping Y chromosome-specific male sex-determining gene dmy. Two different sets of buffers and primers were used and the reactions were conducted in a thermal cycler. The amplified products were separated in 2% agarose gel containing 0.01% ethidium bromide. The gels were viewed on an UV illuminator and the genotypes were identified by visual inspection. The first primer set amplified a 355 bp product for XY genotypes and no amplification for XX. The second set of primers amplified two products; one at 1249 bp and another at 986 bp for XY, and one product at 1249 bp for XX. Experimental data were expressed as means ± SD or SEM, analysed either by one-way analysis of variance (ANOVA) followed by post-hoc Tukey's multiple comparison test or unpaired parametric 't' test including Welch's correction, if distributed normally (lengths and weights), or by Kruskal-Wallis test followed by Man-Whitney's test as post hoc test, if data (stromal follicles in ovary and SPGs and SPTs in testis) did not meet the criteria of using a parametric test. Statistically significant difference were considered for p ≤ 0.05.

Seasonal expression and distribution of kisspeptin1 (kiss1) in the ovary and testis of freshwater catfish, Clarias batrachus: A putative role in steroidogenesis

The central role of kisspeptin (kiss) in mammalian reproduction is well established; however, its intra-gonadal role is poorly addressed. Moreover, studies investigating intra-gonadal role of kiss in fish reproduction are scanty, contradictory and inconclusive. The expression of kiss1 mRNA has been detected in the fish brain, and functionally attributed to the regulation of reproduction, feeding and behavior. The kiss1 mRNA has also been demonstrated in tissues other than the brain in some studies, but its cellular distribution and role at the tissue level have not been adequately addressed in fish. Therefore, an attempt was made in the present study to localize kiss1 in gonadal cells of the freshwater catfish, Clarias batrachus. This study reports the presence of kiss1 in the theca cells and granulosa cells of the ovarian oocytes and interstitial cells in the testis of the catfish. The role of kiss1 in the ovary and testis of the catfish was also investigated using kiss1 receptor (kiss1r) antagonist (p234). The p234 treatment decreased the production of 17β-estradiol in ovary and testosterone in the testis by lowering the activities of 3β-hydroxysteroid dehydrogenase and 17β-hydroxysteroid dehydrogenase under both, in vivo as well as in vitro conditions. The p234 treatment also arrested the progression of oogenesis, as evident from the low number of advancing/advanced oocytes in the treated ovary in comparison to the control ovary. It also reduced the area and perimeter of the seminiferous tubules in the treated catfish testis. Thus, our findings suggest that kiss is involved in the regulation of gonadal steroidogenesis, independent of known endocrine/ autocrine/ paracine regulators, and thereby it accelerates gametogenic processes in the freshwater catfish.

Sex-reversal and Histopathological Assessment of Potential Endocrine-Disrupting Effects of Graphene Oxide on Japanese medaka (Oryzias latipes) Larvae

Sex-ratio is considered as an end point during endocrine disrupting chemicals (EDCs) evaluation. Many fish species including Japanese medaka have XX/XY sex determination mechanism, however, sex reversal (SR) can be induced by external and genetic factors. SR imposed an imbalance in natural sex ratio of a population living in any ecosystem. Considering SR as an end point, we aimed to investigate the potential EDC effects of graphene oxide (GO), a nanocarbon, using Japanese medaka as a model. One-day post-hatch (dph) medaka fries were exposed to GO (2.5, 5.0, 10.0 and 20 mg/L) for 96 h without food, followed by 6 weeks depuration in a GO-free environment with feeding. Phenotypic sex was determined by gonad histology; genotypic sex by genotyping Y-chromosome-specific male sex determining gene, dmy. Our data indicated testes in both XY and XX genotypes, while ovaries were only in XX females. Histopathology of XY and XX testis showed isogenic spermatocysts with active spermatogenesis. Distribution of spermatocytes (SPTs), not the spermatogonium (SPGs), showed enhancement in XY than XX testis. Female phenotypes had single ovary, either in stage 0 or 1. Ovo-testis/testis-ova were absent in XX or XY gonads. GO (2.5-20 mg/L) had inconsistent concentration-dependent effect in both SPGs and SPTs; however, no effect on ovarian follicles. Despite genotypic differences (XY/XX), in the histopathology/histochemistry of liver and kidneys GO effects was found to be minimum. Taken together, present study showed spontaneous induction of SR in some XX genotypes; however, exposure of fasting fries to GO had no apparent EDC effects.

Gametogenic and steroidogenic action of kisspeptin-10 in the Asian catfish, Clarias batrachus: Putative underlying mechanistic cascade

Unlike mammals, two kisspeptins genes encoding, kiss1 and kiss2 are detected in fishes with highly varied and contradictory difference in their reproductive activities. The present study was undertaken to examine the direct action of kisspeptin-10 and its role in gonadal activities in the gonadally quiescent Asian catfish using native mammalian kisspeptin decapeptide (KP-10) involving in vivo and in vitro approaches. The in vivo KP-10 treatment caused precocious onset of gametogenesis and its rapid progression, as was evident from the appearance of advanced stages of ovarian follicles in ovary, and advanced germ cells (spermatocytes/ spermatids) in the testis of the treated Clarias batrachus in comparison to the control gonads. It also elevated the steroid levels in gonads of the catfish in vivo and in vitro conditions. Simultaneously, it increased the expressions of key steroidogenic enzymes like 3β-HSD, 17β-HSD, and StAR protein, responsible for transfer of cholesterol from outer to inner membrane of the mitochondria of steroidogenic cells. Concurrently, it augmented the activities of 3β-HSD and 17β-HSD in the ovarian explants. The expressions of MAPK component (pERK1/2 and ERK1/2) were also up-regulated by KP-10 in gonadal explants. Thus, the data suggest that kisspeptin-10 stimulates gametogenesis by enhancing gonadal steroid production. The study also describes the putative mechanistic cascade of steroidogenic actions of kisspeptin-10 in the catfish so much so in teleost fish. The study also suggests that, kisspeptin may act locally to regulate gonadal activities in an autocrine/paracine manner, independent of known extra-gonadal factors in the catfish.

Vesicle dynamics during the egress of malaria gametocytes from the red blood cell

Malaria parasites are obligate intracellular pathogens that live in human red blood cells harbored by a parasitophorous vacuole. The parasites need to exit from the red blood cell to continue life-cycle progression and ensure human-to-mosquito transmission. Two types of blood stages are able to lyse the enveloping red blood cell to mediate egress, the merozoites and the gametocytes. The intraerythrocytic parasites exit the red blood cell via an inside-out mode during which the membrane of the parasitophorous vacuole ruptures prior to the red blood cell membrane. Membrane rupture is initiated by the exocytosis of specialized secretory vesicles following the perception of egress triggers. The molecular mechanisms of red blood cell egress have particularly been studied in malaria gametocytes. Upon activation by external factors, gametocytes successively discharge at least two types of vesicles, the osmiophilic bodies needed to rupture the parasitophorous vacuole membrane and recently identified egress vesicles that are important for the perforation of the erythrocyte membrane. In recent years, important components of the signaling cascades leading to red blood cell egress have been investigated and several proteins of the osmiophilic bodies have been identified. We here report on the newest findings on the egress of gametocytes from the red blood cell. We further focus on the content and function of the egress-related vesicles and discuss the molecular machinery that might drive vesicle discharge.

Male reproductive systems of Macaca mulatta: Gonadal development, spermatogenesis and applications in spermatogonia stem cell transplantation

Rhesus macaque (Macaca mulatta) is widely applied in animal model construction of infertility, spermatogonia stem cell transplantation and male reproductive diseases. In this review, we describe the seasonal changes of the reproductive system in rhesus macaques, the regular pattern of spermatogenesis and spermatozoa maturation, and the differentiation of spermatogonia and spermatocytes. The duration of the M. mulatta spermatogenesis is approximately 10 days and seminiferous epithelium cycles mainly consist of 12 stages, which provide a suitable model for reproductive studies in non-human primates. Here, we summarize the features of gonadal development and sperm maturation in the rhesus monkeys, which provide important information in the studies of reproductive biology. Rhesus macaque is an excellent animal model in spermatogonia stem cell transplantation. We discuss the applications and progresses of assisted reproductive technologies in sperm liquefaction, semen cryopreservation and spermatogonia stem cell transplantation of rhesus macaques. Besides, we sort out recent proteomic analyses of male reproductive systems and semen samples in rhesus macaques. This review mainly focuses on male reproductive biology and application studies using M. mulatta, which would promote the development of new therapeutic interventions on assisted reproduction and reproductive disease studies in the future.

RNA-seq analysis of the mantle transcriptome from Mytilus edulis during a seasonal spawning event in deep and shallow water culture sites on the northeast coast of Newfoundland, Canada

The blue mussel (Mytilus edulis) has global commercial and ecological importance both in wild and cultured conditions. However there is a qualitative and quantitative lack of knowledge of the molecular mechanisms associated with its reproductive physiology, especially with reference to environmental interactions. Here we initiated a transcriptomic analysis (RNA-sequencing (RNA-seq)) of the mantle from both sexes sampled during a seasonal spawning event and from two culture depths (shallow-5 m; deep- 15 m). Mantle libraries were produced from 3 males and 3 females sampled from each of two shallow sites and two deep sites for a total of 12 replicate male and 12 replicate female libraries (24 total libraries). Overall a total of 2.3 billion raw 100 base reads with an average of 96.5 million reads/library were obtained and assembled into 296,118 transcripts with an average length of 568 bp. Overall, 315 transcripts from male libraries and 25 from female libraries were found to be upregulated in deep water as compared to shallow (edgeR adjusted p value ≤ 0.05). Conversely, 126 transcripts from male libraries and 135 from female libraries were found to be significantly downregulated at the same depth. Thirteen transcripts were selected for qPCR validation based on importance in reproduction, antimicrobial defense and metabolism. Of these, 9 RNA-seq identified transcripts were shown by qPCR to be differentially expressed between groups: 2 were upregulated in deep compared with shallow water (dhx38, mt-co1), 2 were upregulated for female compared with male mantle (pias2, mapkap1) and 6 genes (fndc3a, acbd3, klhl10, ccnb3, armc4, mt-co1) showed to be upregulated in males compared to females. The majority of qPCR studied transcripts were identified as involved in gamete development based on the UniProt database. This study further characterizes the importance of the mantle transcriptome during reproductive activities of M. edulis.

Seasonal variations in biochemical composition and nutritional quality of Crassostrea hongkongensis, in relation to the gametogenic cycle

Variations in the biochemical composition and nutritional quality with annual changes in gonad development were investigated to identify the optimal harvesting time of C. hongkongensis. The glycogen levels in the mantle, muscle, and gonad-visceral mass were significantly lower in June than in December, associated with changes in the expressions of ChGS and ChGP. Protein content consistently exceeded 52% of dry weight. The only significant change in protein levels was an increase between April and June in the gonad-visceral mass, which was associated with the gonadal transition from proliferation to maturation. Moreover, C. hongkongensis consistently had a well-balanced essential amino acid profile, meeting the essential amino acid requirements of preschool children. The lipid content and fatty acid composition of C. hongkongensis varied with the reproductive cycle, but the omega-3:omega-6 ratio was consistently higher than those of C. gigas and C. virginica. In summary, the optimal harvest time of C. hongkongensis was during the inactive stage of most gonads (from August to February at Beihai).

The meiosis-specific MEIOB-SPATA22 complex cooperates with RPA to form a compacted mixed MEIOB/SPATA22/RPA/ssDNA complex

During meiosis, programmed double-strand breaks are repaired by homologous recombination (HR) to form crossovers that are essential to homologous chromosome segregation. Single-stranded DNA (ssDNA) containing intermediates are key features of HR, which must be highly regulated. RPA, the ubiquitous ssDNA binding complex, was thought to play similar roles during mitotic and meiotic HR until the recent discovery of MEIOB and its partner, SPATA22, two essential meiosis-specific proteins. Here, we show that like MEIOB, SPATA22 resembles RPA subunits and binds ssDNA. We studied the physical and functional interactions existing between MEIOB, SPATA22, and RPA, and show that MEIOB and SPATA22 interact with the preformed RPA complex through their interacting domain and condense RPA-coated ssDNA in vitro. In meiotic cells, we show that MEIOB and SPATA22 modify the immunodetection of the two large subunits of RPA. Given these results, we propose that MEIOB-SPATA22 and RPA form a functional ssDNA-interacting complex to satisfy meiotic HR requirements by providing specific properties to the ssDNA.

Reproduction of male reindeer (Rangifer tarandus)

The present review provides a comprehensive assessment on the basic aspects of the reproduction of the Rangifer male with a special focus on pubertal development, and the seasonal dynamics of gametogenesis, androgenesis, antler cycle and other physiological and behavioural characteristics of the rutting male. A greater understanding of the reproductive physiology of the males is needed to improve existing management strategies of semi-domestic stocks in the changing climate and to develop species-specific assisted reproductive technologies for improving the in situ and ex situ conservation programs to preserve endangered subspecies as well as to facilitate the transfer of genetic resources between fragmented wild or semi-domestic populations.

Comparative proteomic analysis of kinesin-8B deficient Plasmodium berghei during gametogenesis

Plasmodium blood stages, responsible for human to vector transmission, termed gametocytes, are the precursor cells that develop into gametes in the mosquito. Male gametogenesis works as a bottleneck for the parasite life cycle, where, during a peculiar and rapid exflagellation, a male gametocyte produces 8 intracellular axonemes that generate by budding 8 motile gametes. Understanding the molecular mechanisms of gametogenesis is key to design strategies for controlling malaria transmission. In the rodent P. berghei, the microtubule-based motor kinesin-8B (PbKIN8B) is essential for flagellum assembly during male gametogenesis and its gene disruption impacts on completion of the parasitic life cycle. In efforts to improve our knowledge about male gametogenesis, we performed an iTRAQ-based quantitative proteomic comparison of P. berghei mutants with disrupted kinesin-8B gene (ΔPbkin8B) and wild type parasites. During the 15 min of gametogenesis, ΔPbkin8B parasites exhibited important motor protein dysregulation that suggests an essential role of PbKIN8B for the correct interaction or integration of axonemal proteins within the growing axoneme. The energy metabolism of ΔPbkin8B mutants was further affected, as well as the response to stress proteins, protein synthesis, as well as chromatin organisation and DNA processes, although endomitoses seemed to occur. SIGNIFICANCE: Malaria continues to be a global scourge, mainly in subtropical and tropical areas. The disease is caused by parasites from the Plasmodium genus. Plasmodium life cycle alternates between female Anopheles mosquitoes and vertebrate hosts through bites. Gametocytes are the parasite blood forms responsible for transmission from vertebrates to vectors. Inside the mosquito midgut, after stimulation, male and female gametocytes transform into gametes resulting in fertilization. During male gametogenesis, one gametocyte generates eight intracytoplasmic axonemes that generate, by budding, flagellated motile gametes involving a process termed exflagellation. Sexual development has a central role in ensuring malaria transmission. However, molecular data on male gametogenesis and particularly on intracytoplasmic axoneme assembly are still lacking. Since rodent malaria parasites permit the combination of in vivo and in vitro experiments and reverse genetic studies, our group investigated the molecular events in rodent P. berghei gametogenesis. The P. berghei motor ATPase kinesin-8B is proposed as an important component for male gametogenesis. We generated Pbkin8B gene-disrupted gametocytes (ΔPbkin8B) that were morphologically similar to the wild- type (WT) parasites. However, in mutants, male gametogenesis is impaired, male gametocytes are disabled in their ability to assemble axonemes and to exflagellate to release gametes, reducing fertilization drastically. Using a comparative quantitative proteomic analysis, we associated the nonfunctional axoneme of the mutants with the abnormal differential expression of proteins essential to axoneme organisation and stability. We also observed a differential dysregulation of proteins involved in protein biosynthesis and degradation, chromatin organisation and DNA processes in ΔPbkin8B parasites, although DNA condensation, mitotic spindle formation and endomitoses seem to occur. This is the first functional proteomic study of a kinesin gene-disrupted Plasmodium parasite providing new insights into Plasmodium male gametogenesis.