ABSTRACT
N6-methyladenosine (m6A) is the most abundant internal modification of mRNAs in eukaryotes. Numerous studies have shown that m6A plays key roles in many biological and pathophysiological processes, including fertility. The factors involved in m6A-dependent mRNA regulation include writers, which deposit the m6A mark, erasers, which remove it, and readers, which bind to m6A-modified transcripts and mediate the regulation of mRNA fate. Many of these proteins are highly expressed in the germ cells of mammals, and some have been linked to fertility disorders in human patients. In this review, we summarise recent findings on the important roles played by proteins involved in m6A biology in mammalian gametogenesis and fertility. Continued study of the m6A pathway in the mammalian germline will shed further light on the importance of epitranscriptomics in reproduction and may lead to effective treatment of human fertility disorders.
Subject(s)
Adenosine , Germ Cells , RNA, Messenger , Adenosine/analogs & derivatives , Adenosine/metabolism , Adenosine/genetics , Animals , Humans , Germ Cells/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Mammals/genetics , Epigenesis, Genetic , Gametogenesis/genetics , Fertility/geneticsABSTRACT
BACKGROUND: Malaria, a global health concern, is caused by parasites of the Plasmodium genus, which undergo gametogenesis in the midgut of mosquitoes after ingestion of an infected blood meal. The resulting male and female gametes fuse to form a zygote, which differentiates into a motile ookinete. After traversing the midgut epithelium, the ookinete differentiates into an oocyst on the basal side of the epithelium. METHODS: Membrane proteins with increased gene expression levels from the gamete to oocyst stages in P. berghei were investigated utilizing PlasmoDB, the functional genomic database for Plasmodium spp. Based on this analysis, we selected the 184-kDa membrane protein, Pb184, for further study. The expression of Pb184 was further confirmed through immunofluorescence staining, following which we examined whether Pb184 is involved in fertilization using antibodies targeting the C-terminal region of Pb184 and biotin-labeled C-terminal region peptides of Pb184. RESULTS: Pb184 is expressed on the surface of male and female gametes. The antibody inhibited zygote and ookinete formation in vitro. When mosquitoes were fed on parasite-infected blood containing the antibody, oocyst formation decreased on the second day after feeding. Synthesized biotin-labeled peptides matching the C-terminal region of Pb184 bound to the female gamete and the residual body of male gametes, and inhibited differentiation into ookinetes in the in vitro culture system. CONCLUSIONS: These results may be useful for the further studying the fertilization mechanism of Plasmodium protozoa. There is also the potential for their application as future tools to prevent malaria transmission.
Subject(s)
Fertilization , Plasmodium berghei , Protozoan Proteins , Plasmodium berghei/genetics , Plasmodium berghei/metabolism , Animals , Female , Male , Protozoan Proteins/genetics , Protozoan Proteins/metabolism , Mice , Germ Cells/metabolism , Malaria/parasitology , Membrane Proteins/metabolism , Membrane Proteins/genetics , Zygote/metabolism , Anopheles/parasitology , Anopheles/metabolism , Oocysts/metabolism , Gametogenesis/geneticsABSTRACT
In vitro gametogenesis (IVG), the reconstitution of germ cell development in vitro, is an emerging stem cell-based technology with profound implications for reproductive science. Despite researchers' long-term goals for future clinical applications, little is currently known about the views of IVG held by the stakeholders potentially most affected by its introduction in humans. We conducted focus groups and interviews with 80 individuals with lived experience of infertility and/or LGBTQ+ family formation in the US, two intersecting groups of potential IVG users. Respondents expressed hope that IVG would lead to higher reproductive success than current assisted reproductive technology (ART), alleviate suffering associated with ART use, and promote greater social inclusion, while expressing concerns predominantly framed in terms of equity and safety. These findings underscore the importance of sustained engagement with stakeholders with relevant experience to anticipate the implications of IVG for research and clinical translation.
Subject(s)
Gametogenesis , Humans , Female , Male , Adult , Infertility/therapy , Stakeholder Participation , Reproductive Techniques, Assisted , Germ CellsABSTRACT
Gametogenesis plays an important role in the reproduction and evolution of species. The transcriptomic and epigenetic alterations in this process can influence the reproductive capacity, fertilization, and embryonic development. The rapidly increasing single-cell studies have provided valuable multi-omics resources. However, data from different layers and sequencing platforms have not been uniformed and integrated, which greatly limits their use for exploring the molecular mechanisms that underlie oogenesis and spermatogenesis. Here, we develop GametesOmics, a comprehensive database that integrates the data of gene expression, DNA methylation, and chromatin accessibility during oogenesis and spermatogenesis in humans and mice. GametesOmics provides a user-friendly website and various tools, including Search and Advanced Search for querying the expression and epigenetic modification(s) of each gene; Tools with Differentially expressed gene (DEG) analysis for identifying DEGs, Correlation analysis for demonstrating the genetic and epigenetic changes, Visualization for displaying single-cell clusters and screening marker genes as well as master transcription factors (TFs), and MethylView for studying the genomic distribution of epigenetic modifications. GametesOmics also provides Genome Browser and Ortholog for tracking and comparing gene expression, DNA methylation, and chromatin accessibility between humans and mice. GametesOmics offers a comprehensive resource for biologists and clinicians to decipher the cell fate transition in germ cell development, and can be accessed at http://gametesomics.cn/.
Subject(s)
DNA Methylation , Databases, Genetic , Gametogenesis , Animals , Humans , Mice , Gametogenesis/genetics , DNA Methylation/genetics , Epigenesis, Genetic/genetics , Male , Germ Cells/metabolism , Female , Spermatogenesis/genetics , Oogenesis/genetics , Genomics/methods , MultiomicsABSTRACT
Gamete formation and subsequent offspring development often involve extended phases of suspended cellular development or even dormancy. How cells adapt to recover and resume growth remains poorly understood. Here, we visualized budding yeast cells undergoing meiosis by cryo-electron tomography (cryoET) and discovered elaborate filamentous assemblies decorating the nucleus, cytoplasm, and mitochondria. To determine filament composition, we developed a "filament identification" (FilamentID) workflow that combines multiscale cryoET/cryo-electron microscopy (cryoEM) analyses of partially lysed cells or organelles. FilamentID identified the mitochondrial filaments as being composed of the conserved aldehyde dehydrogenase Ald4ALDH2 and the nucleoplasmic/cytoplasmic filaments as consisting of acetyl-coenzyme A (CoA) synthetase Acs1ACSS2. Structural characterization further revealed the mechanism underlying polymerization and enabled us to genetically perturb filament formation. Acs1 polymerization facilitates the recovery of chronologically aged spores and, more generally, the cell cycle re-entry of starved cells. FilamentID is broadly applicable to characterize filaments of unknown identity in diverse cellular contexts.
Subject(s)
Gametogenesis , Mitochondria , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae , Aldehyde Dehydrogenase/metabolism , Aldehyde Dehydrogenase/chemistry , Cell Nucleus/metabolism , Cell Nucleus/ultrastructure , Coenzyme A Ligases/metabolism , Cryoelectron Microscopy , Cytoplasm/metabolism , Electron Microscope Tomography , Meiosis , Mitochondria/metabolism , Mitochondria/ultrastructure , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae/ultrastructure , Saccharomyces cerevisiae Proteins/metabolism , Saccharomyces cerevisiae Proteins/chemistry , Spores, Fungal/metabolism , Models, Molecular , Protein Structure, QuaternaryABSTRACT
Differentiation of male gametocytes into flagellated fertile male gametes relies on the assembly of axoneme, a major component of male development for mosquito transmission of the malaria parasite. RNA-binding protein (RBP)-mediated post-transcriptional regulation of mRNA plays important roles in eukaryotic sexual development, including the development of female Plasmodium. However, the role of RBP in defining the Plasmodium male transcriptome and its function in male gametogenesis remains incompletely understood. Here, we performed genome-wide screening for gender-specific RBPs and identified an undescribed male-specific RBP gene Rbpm1 in the Plasmodium. RBPm1 is localized in the nucleus of male gametocytes. RBPm1-deficient parasites fail to assemble the axoneme for male gametogenesis and thus mosquito transmission. RBPm1 interacts with the spliceosome E complex and regulates the splicing initiation of certain introns in a group of 26 axonemal genes. RBPm1 deficiency results in intron retention and protein loss of these axonemal genes. Intron deletion restores axonemal protein expression and partially rectifies axonemal defects in RBPm1-null gametocytes. Further splicing assays in both reporter and endogenous genes exhibit stringent recognition of the axonemal introns by RBPm1. The splicing activator RBPm1 and its target introns constitute an axonemal intron splicing program in the post-transcriptional regulation essential for Plasmodium male development.
Subject(s)
Axoneme , Introns , Protozoan Proteins , RNA Splicing , RNA-Binding Proteins , Introns/genetics , RNA-Binding Proteins/metabolism , RNA-Binding Proteins/genetics , Animals , Protozoan Proteins/genetics , Protozoan Proteins/metabolism , Male , Axoneme/metabolism , Female , Gametogenesis/genetics , Spliceosomes/metabolism , Spliceosomes/genetics , Plasmodium berghei/genetics , Plasmodium berghei/growth & development , Plasmodium berghei/metabolism , Malaria/parasitology , Plasmodium/genetics , Plasmodium/metabolismABSTRACT
Environmental enrichment is used to provide well-being to the animals, such as fish, in captive conditions, mimicking their natural habitat. It may influence fish behavior, physiology, and survival. In terms of reproduction, however, the relationship between environment enrichment and successful reproduction in captivity is still poorly explored in fish species. Aiming to understand any possible benefits of structural enrichment on fish reproduction, 10-days-hatched larvae of the twospot astyanax Astyanax bimaculatus were raised for 18 weeks in tanks with different elements of structural environmental enrichment (PVC pipes, stones, and artificial plants). In the 5th month of life, those animals were hormonally induced to reproduce to assess gamete formation and offspring quality. Animals raised in a sterile-reared environment (non-enriched) showed earlier spawning than the enriched one, presenting significant quantities of Postovulatory follicle complexes (POCs) and cells in atresia in female ovaries, indicating possible reproductive dysfunction or stress, as well as a greater quantity of empty testicular lumen in males, indicating great release of sperm. On the contrary, animals cultivated in enriched environments showed gonads filled with semen in males and vitellogenic oocytes in females. Furthermore, offspring from the sterile-reared group presented significant rates of larval abnormality compared to the enriched group. In conclusion, the results of this study show that environmental enrichment can interfere with the reproduction of fish in captivity, mainly by preventing early maturation of gametes, which can result in low-quality offspring and, consequently, low production of fish species.
Subject(s)
Characidae , Gametogenesis , Reproduction , Animals , Female , Male , Gametogenesis/physiology , Reproduction/physiology , Characidae/physiology , Environment , AquacultureABSTRACT
Sexually reproducing eukaryotes employ a developmentally regulated cell division program-meiosis-to generate haploid gametes from diploid germ cells. To understand how gametes arise, we generated a proteomic census encompassing the entire meiotic program of budding yeast. We found that concerted waves of protein expression and phosphorylation modify nearly all cellular pathways to support meiotic entry, meiotic progression, and gamete morphogenesis. Leveraging this comprehensive resource, we pinpointed dynamic changes in mitochondrial components and showed that phosphorylation of the FoF1-ATP synthase complex is required for efficient gametogenesis. Furthermore, using cryoET as an orthogonal approach to visualize mitochondria, we uncovered highly ordered filament arrays of Ald4ALDH2, a conserved aldehyde dehydrogenase that is highly expressed and phosphorylated during meiosis. Notably, phosphorylation-resistant mutants failed to accumulate filaments, suggesting that phosphorylation regulates context-specific Ald4ALDH2 polymerization. Overall, this proteomic census constitutes a broad resource to guide the exploration of the unique sequence of events underpinning gametogenesis.
Subject(s)
Gametogenesis , Meiosis , Proteome , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae , Phosphorylation , Proteome/metabolism , Gametogenesis/genetics , Saccharomyces cerevisiae Proteins/metabolism , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae/genetics , Proteomics/methods , Mitochondria/metabolism , Gene Expression Regulation, Fungal , Saccharomycetales/metabolism , Saccharomycetales/geneticsABSTRACT
Cytoplasmic polyadenylation plays a vital role in gametogenesis; however, the participating enzymes and substrates in mammals remain unclear. Using knockout and knock-in mouse models, we describe the essential role of four TENT5 poly(A) polymerases in mouse fertility and gametogenesis. TENT5B and TENT5C play crucial yet redundant roles in oogenesis, with the double knockout of both genes leading to oocyte degeneration. Additionally, TENT5B-GFP knock-in females display a gain-of-function infertility effect, with multiple chromosomal aberrations in ovulated oocytes. TENT5C and TENT5D both regulate different stages of spermatogenesis, as shown by the sterility in males following the knockout of either gene. Finally, Tent5a knockout substantially lowers fertility, although the underlying mechanism is not directly related to gametogenesis. Through direct RNA sequencing, we discovered that TENT5s polyadenylate mRNAs encoding endoplasmic reticulum-targeted proteins essential for gametogenesis. Sequence motif analysis and reporter mRNA assays reveal that the presence of an endoplasmic reticulum-leader sequence represents the primary determinant of TENT5-mediated regulation.
Subject(s)
Gametogenesis , Mice, Knockout , Polyadenylation , RNA, Messenger , Spermatogenesis , Animals , Female , Male , RNA, Messenger/metabolism , RNA, Messenger/genetics , Mice , Spermatogenesis/genetics , Gametogenesis/genetics , Oogenesis/genetics , Polynucleotide Adenylyltransferase/metabolism , Polynucleotide Adenylyltransferase/genetics , Oocytes/metabolism , Fertility/genetics , Mice, Inbred C57BLABSTRACT
Cellular proteins and the mRNAs that encode them are key factors in oocyte and sperm development, and the mechanisms that regulate their translation and degradation play an important role during early embryogenesis. There is abundant evidence that expression of microRNAs (miRNAs) is crucial for embryo development and are highly involved in regulating translation during oocyte and early embryo development. MiRNAs are a group of short (18-24 nucleotides) non-coding RNA molecules that regulate post-transcriptional gene silencing. The miRNAs are secreted outside the cell by embryos during preimplantation embryo development. Understanding regulatory mechanisms involving miRNAs during gametogenesis and embryogenesis will provide insights into molecular pathways active during gamete formation and early embryo development. This review summarizes recent findings regarding multiple roles of miRNAs in molecular signaling, plus their transport during gametogenesis and embryo preimplantation.
Subject(s)
Embryonic Development , MicroRNAs , Reproductive Techniques, Assisted , MicroRNAs/genetics , MicroRNAs/metabolism , Humans , Embryonic Development/genetics , Animals , Oocytes/metabolism , Female , Gene Expression Regulation, Developmental , Gametogenesis/genetics , MaleABSTRACT
Gamete development is a precisely programmed process in Cryptosporidium parvum, a leading cause of diarrheal disease worldwide. Nava et al. recently described the developmentally regulated expression of CDPK5 during male gametogenesis. Here we discuss their main findings, posing this protein kinase as a promising target for antiparasitic interventions.
Subject(s)
Cryptosporidium parvum , Gametogenesis , Male , Cryptosporidium parvum/genetics , Cryptosporidium parvum/physiology , Protozoan Proteins/metabolism , Protozoan Proteins/genetics , Animals , Humans , Cryptosporidiosis/parasitologyABSTRACT
Nitric oxide (NO) is a gaseous molecule that regulates various reproductive functions. It is a well-recognized regulator of GnRH-FSH/LH-sex steroid secretion in vertebrates including fish. Kisspeptin is a recently discovered neuropeptide which also regulates GnRH secretion. Nitrergic and kisspeptin neurons are reported in close physical contact in the mammalian brain suggesting their interactive role in the release of GnRH. The existence of kisspeptin and NOS is also demonstrated in vertebrate gonads, but information on their reciprocal relation in gonads, if any, is obscure. Therefore, attempts were made to evaluate the functional reciprocal relation between nitric oxide and kisspeptin in the catfish gonads, if any, by administering the nitric oxide synthase (NOS) inhibitor, L-NAME {N(G)-nitro-L-arginine methyl ester}, which reduces NO production, and kisspeptin agonist (KP-10) and assessing their impacts on the expressions of kisspeptin1, different NOS isoforms, NO and steroid production in the gonadal tissue. The results revealed that L-NAME suppressed the expression of kiss1 in gonads of the catfish establishing the role of NO in kisspeptin expression. However, KP-10 increased the expression of all the isoforms of NOSs (iNOS, eNOS, nNOS) and concurrently NO and steroids in the ovary and testis. In vitro studies also indicate that kisspeptin stimulates the production of NO and estradiol and testosterone levels in the gonadal explants and medium. Thus, in vivo results clearly suggest a reciprocal interaction between kisspeptin and NO to regulate the gonadal activity of the catfish. The in vitro findings further substantiate our contention regarding the interactive role of kisspeptin and NO in gonadal steroidogenesis.
Subject(s)
Catfishes , Gametogenesis , Kisspeptins , NG-Nitroarginine Methyl Ester , Nitric Oxide , Animals , Nitric Oxide/metabolism , Catfishes/metabolism , Kisspeptins/metabolism , Male , NG-Nitroarginine Methyl Ester/pharmacology , Female , Gametogenesis/drug effects , Steroids/biosynthesis , Nitric Oxide Synthase/metabolism , Testis/metabolism , Testis/drug effects , Gonads/metabolism , Gonads/drug effects , Ovary/metabolismABSTRACT
Most Pacific salmon species grow in the ocean, return to their native rivers to reproduce, and then die (semelparous type). However, rainbow trout survive after spawning and reproduce repeatedly until the end of their lives (iteroparous type). Little is known about how germline stem cells behave during gametogenesis in the two types of Pacific salmon. In this study, we show that all germline stem cells disappear after the first gametogenesis in Chinook and Kokanee salmon, whereas germline stem cells are maintained in rainbow trout. However, the germline stem cells of Chinook and Kokanee salmon transplanted into rainbow trout survive even after their spawning seasons and supply salmon gametes for multiple years. These results indicate that the behavior of the germline stem cells is mainly regulated by the somatic environment.
Subject(s)
Oncorhynchus mykiss , Salmon , Animals , Germ Cells , Reproduction , Female , Male , Gametogenesis , Stem Cells/cytology , Stem Cells/metabolismABSTRACT
The study of the functional genome in mice and humans has been instrumental for describing the conserved molecular mechanisms regulating human reproductive biology, and for defining the etiologies of monogenic fertility disorders. Infertility is a reproductive disorder that includes various conditions affecting a couple's ability to achieve a healthy pregnancy. Recent advances in next-generation sequencing and CRISPR/Cas-mediated genome editing technologies have facilitated the identification and characterization of genes and mechanisms that, if affected, lead to infertility. We report established genes that regulate conserved functions in fundamental reproductive processes (e.g., sex determination, gametogenesis, and fertilization). We only cover genes the deletion of which yields comparable fertility phenotypes in both rodents and humans. In the case of newly-discovered genes, we report the studies demonstrating shared cellular and fertility phenotypes resulting from loss-of-function mutations in both species. Finally, we introduce new model systems for the study of human reproductive biology and highlight the importance of studying human consanguineous populations to discover novel monogenic causes of infertility. The rapid and continuous screening and identification of putative genetic defects coupled with an efficient functional characterization in animal models can reveal novel mechanisms of gene function in human reproductive tissues.
Subject(s)
Fertilization , Gametogenesis , Sex Differentiation , Humans , Gametogenesis/genetics , Animals , Fertilization/genetics , Sex Differentiation/genetics , Conserved Sequence/genetics , Female , MaleABSTRACT
Formation of the synaptonemal complex (SC) is a prerequisite for proper recombination and chromosomal segregation during meiotic prophase I. One mechanism that ensures SC formation is chromosomal movement, which is driven by the force derived from cytoskeletal motors. Here, we report the phenotype of medaka mutants lacking the telomere repeat binding bouquet formation protein 1 (TERB1), which, in combination with the SUN/KASH protein, mediates chromosomal movement by connecting telomeres and cytoskeletal motors. Mutations in the terb1 gene exhibit defects in SC formation in medaka. Although SC formation was initiated, as seen by the punctate lateral elements and fragmented transverse filaments, it was not completed in the terb1 mutant meiocytes. The mutant phenotype further revealed that the introduction of double strand breaks was independent of synapsis completion. In association with these phenotypes, meiocytes in both the ovaries and testes exhibited an aberrant arrangement of homologous chromosomes. Interestingly, although oogenesis halted at the zygotene-like stage in terb1 mutant, testes continued to produce sperm-like cells with aberrant DNA content. This indicates that the mechanism of meiotic checkpoint is sexually different in medaka, similar to the mammalian checkpoint in which oogenesis proceeds while spermatogenesis is arrested. Moreover, our results suggest that spermatogenesis is mechanistically dissociable from meiosis.
Subject(s)
Gametogenesis , Mutation , Oryzias , Synaptonemal Complex , Animals , Oryzias/genetics , Synaptonemal Complex/genetics , Synaptonemal Complex/metabolism , Male , Gametogenesis/genetics , Female , Meiosis , Fish Proteins/genetics , Fish Proteins/metabolismABSTRACT
Pesticides threat marine organisms worldwide. Among them, the Pacific oyster is a bivalve mollusc model in marine ecotoxicology. A large body of literature already stated on the multiple-scale effects pesticides can trigger in the Pacific oyster, throughout its life cycle and in a delayed manner. In particular, reproductive toxicity is of major concern because of its influence on population dynamics. However, past studies mostly investigated pesticide reprotoxicity as a direct effect of exposure during gametogenesis or directly on gametes and little is known about the influence of an early embryo exposure on the breed capacity. Therefore, we studied delayed and multigenerational consequences through gametogenesis features (i.e. sex ratio, glycogen content, gene expression) and reproductive success in two consecutive oyster generations (F0 and F1) exposed to an environmentally-relevant pesticide mixture (sum nominal concentration: 2.85 µg.L-1) during embryo-larval development (0-48 h post fertilization, hpf). In the first generation, glycogen content increased in exposed individuals and the expression of some gametogenesis target genes was modified. The reproductive success measured 48 hpf was higher in exposed individuals. A multigenerational influence was observed in the second generation, with feminisation, acceleration of gametogenesis processes and the sex-specific modification of glycogen metabolism in individuals from exposed parents. This study is the first to highlight the delayed effects on reproduction induced by an early exposure to pesticides, and its multigenerational implications in the Pacific oyster. It suggests that environmental pesticide contamination can have impacts on the recruitment and the dynamics of natural oyster populations exposed during their embryo-larval phase.
Subject(s)
Pesticides , Reproduction , Water Pollutants, Chemical , Animals , Reproduction/drug effects , Water Pollutants, Chemical/toxicity , Pesticides/toxicity , Crassostrea/drug effects , Crassostrea/physiology , Gametogenesis/drug effects , Female , Male , Glycogen/metabolismABSTRACT
The protozoan parasite Cryptosporidium is a leading cause of diarrhea in young children. The parasite's life cycle involves a coordinated and timely progression from asexual to sexual stages, leading to the formation of the transmissible oocyst. Underlying molecular signaling mechanisms orchestrating sexual development are not known. Here, we describe the function of a signaling kinase in Cryptosporidium male gametogenesis. We reveal the expression of Cryptosporidium parvum calcium-dependent protein kinase 5 (CDPK5) during male gamete development and its important role in the egress of mature gametes. Genetic ablation of this kinase results in viable parasites, indicating that this gene is dispensable for parasite survival. Interestingly, cdpk5 deletion decreases parasite virulence and impacts oocyst shedding in immunocompromised mice. Using phosphoproteomics, we identify possible CDPK5 substrates and biological processes regulated by this kinase. Collectively, these findings illuminate parasite cell biology by revealing a mechanism controlling male gamete production and a potential target to block disease transmission.
Subject(s)
Gametogenesis , Protozoan Proteins , Animals , Male , Mice , Virulence , Protozoan Proteins/metabolism , Protozoan Proteins/genetics , Cryptosporidium parvum/pathogenicity , Cryptosporidium parvum/enzymology , Protein Kinases/metabolism , Protein Kinases/genetics , Cryptosporidiosis/parasitology , Humans , Signal TransductionABSTRACT
The cellular and molecular mechanisms governing sexual reproduction are conserved across eukaryotes. Nevertheless, hybridization can disrupt these mechanisms, leading to asexual reproduction, often accompanied by polyploidy. In this study, we investigate how ploidy level and ratio of parental genomes in hybrids affect their reproductive mode. We analyze the gametogenesis of sexual species and their diploid and triploid hybrids from the freshwater fish family Cobitidae, using newly developed cytogenetic markers. We find that diploid hybrid females possess oogonia and oocytes with original (diploid) and duplicated (tetraploid) ploidy. Diploid oocytes cannot progress beyond pachytene due to aberrant pairing. However, tetraploid oocytes, which emerge after premeiotic genome endoreplication, exhibit normal pairing and result in diploid gametes. Triploid hybrid females possess diploid, triploid, and haploid oogonia and oocytes. Triploid and haploid oocytes cannot progress beyond pachytene checkpoint due to aberrant chromosome pairing, while diploid oocytes have normal pairing in meiosis, resulting in haploid gametes. Diploid oocytes emerge after premeiotic elimination of a single-copied genome. Triploid hybrid males are sterile due to aberrant pairing and the failure of chromosomal segregation during meiotic divisions. Thus, changes in ploidy and genome dosage may lead to cyclical alteration of gametogenic pathways in hybrids.
Subject(s)
Cypriniformes , Triploidy , Animals , Female , Male , Tetraploidy , Gametogenesis , Haploidy , Cypriniformes/geneticsABSTRACT
BACKGROUND: Epigenetic marks are reprogrammed during sexual reproduction. In flowering plants, DNA methylation is only partially remodeled in the gametes and the zygote. However, the timing and functional significance of the remodeling during plant gametogenesis remain obscure. RESULTS: Here we show that DNA methylation remodeling starts after male meiosis in rice, with non-CG methylation, particularly at CHG sites, being first enhanced in the microspore and subsequently decreased in sperm. Functional analysis of rice CHG methyltransferase genes CMT3a and CMT3b indicates that CMT3a functions as the major CHG methyltransferase in rice meiocyte, while CMT3b is responsible for the increase of CHG methylation in microspore. The function of the two histone demethylases JMJ706 and JMJ707 that remove H3K9me2 may contribute to the decreased CHG methylation in sperm. During male gametogenesis CMT3a mainly silences TE and TE-related genes while CMT3b is required for repression of genes encoding factors involved in transcriptional and translational activities. In addition, CMT3b functions to repress zygotic gene expression in egg and participates in establishing the zygotic epigenome upon fertilization. CONCLUSION: Collectively, the results indicate that DNA methylation is dynamically remodeled during male gametogenesis, distinguish the function of CMT3a and CMT3b in sex cells, and underpin the functional significance of DNA methylation remodeling during rice reproduction.
Subject(s)
DNA Methylation , Oryza , Oryza/genetics , Oryza/metabolism , Seeds/metabolism , Methyltransferases/metabolism , Gametogenesis , Gene Expression Regulation, PlantABSTRACT
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.