Project description:In this work, we analyzed DNA methylation in rice male meiocyte, microspore and sperm and studied the function of a set of chromatin regulators during the process. The results indicate that that DNA methylation remodeling started after meiosis of the male meiocytes and that non-CG, particularly CHG, methylation is dynamically remodeling during rice male gametogenesis. The work reveals distinct function of DNA methyltransfesaes and histone demethylase in the remodeling of CHG methylation and suggests that the CHG methylation remodeling has functional significance for male gametogenesis and fertilization.
Project description:The atypical protein kinase Haspin phosphorylates Histone H3 at threonine-3 (H3T3ph) during mitosis. H3T3ph creates a docking site for the Chromosomal Passenger Complex at the inner centromere, enabling correction of erratic microtubule-chromosome contacts and preventing chromosome mis-segregation. Surprisingly, Haspin knockout in the mouse does not cause developmental defects, except for testicular anomalies. Therefore, the physiological role of this kinase and the mechanistic significance of H3T3ph are in question. We show here that mouse embryonic stem cells that lack or overexpress Haspin are prone to chromosome misalignment. However, the cell population as a whole maintains the ability to expand and differentiate into multiple lineages. Although not essential for pluripotency, Haspin affects the expression of several testis-specific genes. Furthermore, the H3T3ph mark is detected in under-condensed chromatin domains of haploid spermatids, in cis with lysine/arginine methylation marks. We propose that Haspin controls a compound phospho-methyl switch and regulates testis-specific transcription.
Project description:To study the dynamic of DNA methylation during male gametogenesis 9 stages of germ cells were purified, then DNA samples (n=4/stage) were analyzed by Rat Methyl seq capture
Project description:Condensin is a multi-subunit protein complex regulating chromosome condensation and segregation during cell division. In Plasmodium spp., the causative agent of malaria, cell division is atypical and the role of condensin is unclear. Here we examine the role of SMC2 and SMC4, the core subunits of condensin, during endomitosis in schizogony and endoreduplication in male gametogenesis. During early schizogony SMC2/SMC4 localize to a distinct focus, identified as the centromeres by NDC80 fluorescence and ChIP-seq analyses, but do not form condensin I or II complexes. In mature schizonts and during male gametogenesis there is a diffuse SMC2/SMC4 distribution on chromosomes and in the nucleus, and both condensin I and II complexes form at these stages. Knockdown of smc2 and smc4 gene expression revealed essential roles in parasite proliferation and transmission. The condensin core subunits (SMC2/SMC4) form different complexes and may have distinct functions at various stages of the parasite life cycle.
Project description:Background Triploidy can occur in all species but is often lethal in birds and mammals. In amphibian, invertebrates and numerous species of fishes, triploid animals are viable and undistinguishable from diploid individuals. Gametogenesis is often affected and most animals are sterile for at least one sex, and gametes for the other sex are often unfertile. Although the majority of triploid oysters are sterile (beta individuals, 3nb), a low but persistent proportion of male and female animals produce gametes (alpha individuals, 3na). Thus, oysters constitute a unique model to study the effect of triploidy on germ cells development of both male and females. In this study, we used microarray to study the consequences of polyploidy on triploid oyster germ cells mitosis and meiosis. Results We compared the transcriptome of gonads of 3na and 3nb oyster gonads over the course of gametogenesis to the transcriptome of diploid (2n) oyster gonads. This study allowed us to reveal an increase in DNA repair and apoptosis through the NF-kappaB pathway, and a decrease in actin remodeling and chromatin remodeling in all 3n oysters. The comparison of 3na and 3nb individuals with 2n revealed that a pachytene checkpoints may be responsible for the success in gametogenesis of 3na individuals and for the observed delay in gametogenesis. However, the sterility of 3nb individuals can be explained by a disruption of sex determinism mechanisms. Indeed 3nb females express male-specific genes including enkurin and an Elav-like gene, and 3nb males express female-specific genes including Forkhead box L2 and beta-catenin. Conclusions Our results bring back to the front of the research field the questions of genetic sex determinism, mitosis/meiosis control, pachytene checkpoint, and cell type specific DNA damage pathways. Furthermore, this study identifies numerous new candidate genes which function should now be studied in details in oysters and in other triploid animals in order to elucidate the complex mechanisms involved in the regulation of triploid cells division. Triploid spats were obtained by crossing tetraploid males and diploid females in the ifremer experimental hatchery (La tremblade, Charente Maritime, France). We performed microarray analysis on a total of 35 individual triploid gonads that can be grouped as follow: 3n stage 0 (4 individuals), 3n alpha Stage 1 (8 individuals), 3n beta Stage 1 (8 individuals), 3n alpha Stage 3 male (4 individuals), 3n beta Stage 3 male (3 individuals), 3n alpha Stage 3 female (4 individuals), and 3n beta stage 3 female (4 individuals).
Project description:DNA methylation is an essential component of transposable element (TE) silencing, yet the mechanism by which methylation causes transcriptional repression remains poorly understood. Here we study the Arabidopsis thaliana Methyl-CpG Binding Domain (MBD) proteins MBD1, MBD2, and MBD4, and show that MBD2 acts as a transposable element (TE) repressor during male gametogenesis. MBD2 bound chromatin regions containing high levels of CG methylation, and MBD2 was capable of silencing the FWA gene when tethered to its promoter. MBD2 loss caused TE activation in the vegetative cell (VC) of mature pollen without affecting DNA methylation levels, demonstrating that MBD2-mediated silencing acts strictly downstream of DNA methylation. Loss of silencing in mbd2 became more significant in the mbd5 mbd6 or adcp1 mutant backgrounds, as well as in plants with chemically induced genome-wide DNA demethylation, suggesting that MBD2 acts redundantly with other silencing pathways to safeguard TEs from activation. Overall, our study identifies MBD2 as a novel methyl reader that acts downstream of DNA methylation to silence TEs during male gametogenesis.
Project description:Background Triploidy can occur in all species but is often lethal in birds and mammals. In amphibian, invertebrates and numerous species of fishes, triploid animals are viable and undistinguishable from diploid individuals. Gametogenesis is often affected and most animals are sterile for at least one sex, and gametes for the other sex are often unfertile. Although the majority of triploid oysters are sterile (beta individuals, 3nb), a low but persistent proportion of male and female animals produce gametes (alpha individuals, 3na). Thus, oysters constitute a unique model to study the effect of triploidy on germ cells development of both male and females. In this study, we used microarray to study the consequences of polyploidy on triploid oyster germ cells mitosis and meiosis. Results We compared the transcriptome of gonads of 3na and 3nb oyster gonads over the course of gametogenesis to the transcriptome of diploid (2n) oyster gonads. This study allowed us to reveal an increase in DNA repair and apoptosis through the NF-kappaB pathway, and a decrease in actin remodeling and chromatin remodeling in all 3n oysters. The comparison of 3na and 3nb individuals with 2n revealed that a pachytene checkpoints may be responsible for the success in gametogenesis of 3na individuals and for the observed delay in gametogenesis. However, the sterility of 3nb individuals can be explained by a disruption of sex determinism mechanisms. Indeed 3nb females express male-specific genes including enkurin and an Elav-like gene, and 3nb males express female-specific genes including Forkhead box L2 and beta-catenin. Conclusions Our results bring back to the front of the research field the questions of genetic sex determinism, mitosis/meiosis control, pachytene checkpoint, and cell type specific DNA damage pathways. Furthermore, this study identifies numerous new candidate genes which function should now be studied in details in oysters and in other triploid animals in order to elucidate the complex mechanisms involved in the regulation of triploid cells division.