Intercellular bridges are essential for transposon repression and meiosis in the male germline
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PROVIDER: PRJNA1148642 | ENA |
REPOSITORIES: ENA
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Project description:Germ cell connectivity via intercellular bridges is a widely conserved feature but its functional significance is poorly understood. Intercellular bridges are essential for fertility in male mice as genetic ablation of a critical bridge component, TEX14, causes loss of germ cell connectivity and meiotic failure, however the underlying reasons are unknown. A screen for meiosis-defective mouse mutants yielded a sterile mutant harboring a point mutation in Tex14 that leads to a partial loss of germ cell intercellular bridges. We utilized the Tex14 hypomorphs with reduced intercellular bridges, along with Tex14-null mice that completely lack bridges to examine the roles of germ cell connectivity during adult spermatogenesis. Complete or partial loss of intercellular bridges does not severely deplete spermatogonia, but spermatocytes are unable to undergo meiotic DNA replication and enter meiotic prophase. Phenotypic severity correlates with the extent of intercellular bridge depletion, with Tex14 hypomorphs containing a relatively larger number of spermatocytes undergoing meiosis, thus allowing us to assess impacts on meiotic progression. Tex14-deficient germ cells that enter prophase form meiotic breaks and initiate synapsis, but later exhibit synaptic failures and retain unrepaired breaks. Strikingly, Tex14-deficient germ cells derepress LINE1 retrotransposons and accumulate LINE1-encoded proteins during meiosis. Single-cell RNA-sequencing of testes from Tex14 hypomorphs show that intercellular bridge depletion modestly impacts the RNA landscape in early germ cell stages, while mutant cells that progress to late spermatocyte and post-meiotic spermatid stages broadly upregulate retrotransposons and dysregulate gene expression. RNA-sequencing confirms extensive sharing of transcripts between normal spermatids and demonstrates its partial attenuation in Tex14 hypomorphs, indicating that intercellular bridges enable exchange of cytoplasmic material between connected germ cells in testes. Tex14 hypomorphs display a progressive decline in germ cell numbers starting from the spermatocyte stage, with a complete lack of elongating spermatids, and are therefore sterile. Our findings reveal that the regulation of meiosis is non-cell-intrinsic and inform a model in which intercellular bridges orchestrate critical meiotic events and protect germline genome integrity during spermatogenesis, possibly by facilitating the exchange of regulatory factors.
2025-01-06 | GSE274959 | GEO
Project description:Intercellular bridges coordinate the transition from pluripotency to meiosis in mouse fetal oocytes
| PRJNA699296 | ENA
Project description:Purpose: Investigate the transcriptomes of Tex14 heterogygous sample (with intercellular bridges intact) compared to Tex14 homozygous mutant (lacking intracellular bridges) to ascertain what effects the loss of cytoplasmic sharing has on mitotic to meiotic mouse ovary Methods: Single cell RNA sequencing libaries were created from embryonic day 13.5 mouse ovaries from Tex14 +/- and Tex14 -/- samples. Three Tex14+/- and two Tex14-/- E13.5 ovaries were pooled. Libaries were creating using 10X Chromium Single Cell 3' (v2 Chemistry) library kits per 10X posted protocols. Samples were sequenced on HiSeq 4000 (Illumina) with paired-end sequencing parameters: Read1, 98 cycles; Index1, 14 cycles; Index2, 8 cycles; and Read2, 10 cycles. Tex14+/- sample had 23,567 mean reads per cell, and Tex14-/- had 19,735 mean reads per cell. Since 10X Genomics recommends an average of 60k raw reads per cell, we submitted our two libaries for deeper sequencing. Our second sequencing run was done on a Novaseq S2 flowcell with the following parameters: Read 1 Length 26bp; Index 1 Length 8bp; Index 2 Length 0bp; Read 2 Length: 98 bp. Follwing deeper sequencing, Tex14+/- sample had 55,744 mean reads per cell, and Tex14-/- had 41,117 mean reads per cell. Cells which passed quality control metrics were further analyzed. Results: We used CellRanger v2.1.0 to align the sequenced data to the 10X Genomics pre-built mm10 genome. We mapped about 300,000,000 sequence reads for each shallowly sequenced library, and 750-800,000,000 reads for the deeply sequenced libraries. We used Seurat v3 to keep high quality cells, excluding cells which did not all of the following metrics: genes expressed in at least 3 cells, fewer than 25,000 unique fragments (to exclude cell doublets), greater than 200 genes expressed (to exclude GEMS with no cells), and cells with 7.0% or less mitochondrial gene expression. After quality control exclusion, cell counts for the gene by cell matrices are as follows: tex14 het shallow, 12260 cells; tex14 ko shallow, 14715 cells; tex14 het deep, 11794 cells; tex14 ko deep, 13982 cells. Conclusions: Our study represents the first single cell RNA sequencing experiment conducted on fetal mouse ovaries lacking intracellular bridges. We observed that the absence of Tex14 did not alter the transcriptional composition of ovarian somatic cells, but specifically attenuated the level of pluripotency-associated transcripts as germ cells enter meiosis.
2021-04-06 | GSE166121 | GEO
Project description:The Sleeping Beauty transposon system was established as a robust and efficient method for germline transgenesis in different mammalian species. The generation of transgenic mice, rats, rabbits and swine carrying an identical Venus reporter construct delivered by transposon-mediated gene transfer enables comparative studies of gene expression in these lines of mammalian models. Whereas comparable expression patterns of the Venus reporter were found in somatic tissues, preliminary studies suggested that a striking difference in reporter expression may exist in mature spermatozoa of these species. Here we clearly show the differential expression of Venus reporter protein during spermatogenesis of the two compared species, the laboratory rabbit and mice. We provide evidence for the functionality of intercellular bridges in the male germline and genotype-independent transgenic phenotype of rabbit spermatids. Our data suggest that the reporter rabbit line may be a suitable tool to identify molecular mechanisms in testicular development, and may contribute to develop better animal models for male infertility in men.
| S-EPMC4858258 | biostudies-literature
Project description:Metastasis is a major cause of mortality, and remains a final frontier in the search for a cure for cancer. While there has been much research on the ‘seed’ (metastatic tumor cells) and the ‘soil’ (colonized host tissue), interactions between metastatic cancer cells and stromal endothelial cells, which occur at multiple stages during metastasis, are less well understood. Here we report a dynamic regulation of the endothelium by cancer cells through the formation of nanoscale intercellular membrane bridges, which act as physical conduits for intercellular communication in vitro and in vivo, including horizontal transfer of microRNAs (miRNA). The communication between the tumor cell and the endothelium upregulates markers associated with pathological endothelium, which is reversed by pharmacological inhibition of these nanoscale conduits. These results lead us to define the notion of “metastatic hijack”: cancer cell-induced transformation of healthy endothelium into pathological endothelium via horizontal communication through the nanoscale conduits. Pharmacological perturbation of these nanoscale membrane bridges decreases metastatic foci in syngeneic- and human xenograft-breast cancer models. Targeting the formation of these nanoscale membrane bridges may potentially emerge as a new therapeutic opportunity in the management of metastatic cancer. A miRNA microarray was used to evaluate the transport of endogenous microRNAs. The intercellular transfer-ve and intercellular transfer+ve samples were sorted from the same endothelial cell population with the only difference being the occurrence of intercellular transport. The heat map shows potential miRNA candidates for exogenous transfer on two independent biological replicates. These miRNA candidates were significantly up-regulated in the cells receiving transfer of intercellular contents. HUVECs that were not exposed to cancer cells were used as a baseline control.
2015-09-04 | E-GEOD-72679 | biostudies-arrayexpress
Project description:Meiosis is precisely controlled by complex gene expression programs and involves epigenetic reprogramming and silencing of transposable elements. ASH2L (Absent, small or homeotic 2-like) is a core component of KMT2 complexes conferring H3K4 trimethylation, and plays key roles in mouse embryonic development, neurogenesis, and liver function. However, its role in meiosis remains elusive. Here, we demonstrate an essential role of Ash2l for meiosis. Using a germ cell-specific Ash2l knockout mouse model, we found that Ash2l deficiency leads to meiotic arrest and sterility in both sexes. Ash2l-deficient spermatocytes exhibit failures in chromosomal synapsis, blockades in meiotic recombination, and increased apoptosis. Mechanistically, we found that the Ash2l deficiency results in a global loss of H3K4me3 in promoter regions and significantly decreases expression of thousands of genes, including those for H3K9 di-methylation, DNA methylation and transposon repression, crucial for meiotic prophase I progression. Furthermore, we observed that Ash2l mutant spermatocytes display hypomethylation at transposon sites and ectopic expression of LINE1-ORF1P. Our findings thus reveal a previously unappreciated role of the ASH2L-dependent H3K4me3 modification and provide clues to the molecular mechanisms in epigenetic disorders underlying male infertility.
2024-10-19 | GSE246296 | GEO
Project description:Meiosis is critical to generating oocytes however, the mechanisms regulating the switch from mitotic primordial germ cells (PGCs) to meiotic germ cells are poorly understood in females. We showed that the onset of meiosis in the fetal murine ovary propagates via intercellular bridges between developing germ cells by using Tex14 mutant (Tex14-/-) mice. Tex14-/- germ cells, which lack intercellular bridges, initiates meiosis prematurely and they more rapidly extinguish pluripotency-associated transcripts (such as Dppa3) upon entering meiosis. Considering the involvement of Dppa3 in methylation process as well as the importance of epigenetic reprogramming for gamete formation and meiosis, we isolated Tex14 wild-type, heterozygous and mutant germ cells from E13.0 and E13.5 ovaries for whole genome bisulfite sequencing. We compared how methylation differs between age-matched wild-type/heterozygous controls and mutants. We find that DNA methylation across the genome is not affected in Tex14 mutant germ cells however, promoters of Germline Reprogramming Responsive (GRR) genes and younger L1 genes are hypomethylated. These results suggest that cytoplasmic sharing via intercellular bridges slows and coordinates the cell state transition from pluripotency to meiosis potentially by diluting regulatory factors of epigenetic reprogramming.
2021-04-06 | GSE165010 | GEO
Project description:Transcriptional silencing by heritable cytosine-5 methylation is an ancient strategy to repress transposable elements. It was previously thought that mammals possess four DNA methyltransferase paralogs—Dnmt1, Dnmt3a, Dnmt3b and Dnmt3l—that establish and maintain cytosine-5 methylation. Here we identify a fifth paralog, Dnmt3c, that is essential for retrotransposon methylation and repression in the mouse male germline. From a phenotype-based forward genetics screen, we isolated a mutant mouse called ‘rahu’, which displays severe defects in double-strand-break repair and homologous chromosome synapsis during male meiosis, resulting in sterility. rahu is an allele of a transcription unit (Gm14490, renamed Dnmt3c) that was previously mis-annotated as a Dnmt3-family pseudogene. Dnmt3c encodes a cytosine methyltransferase homolog, and Dnmt3crahu mutants harbor a non-synonymous mutation of a conserved residue within one of its cytosine methyltransferase motifs, similar to a mutation in human DNMT3B observed in patients with immunodeficiency, centromeric instability and facial anomalies syndrome. The rahu mutation lies at a potential dimerization interface and near the potential DNA binding interface, suggesting that it compromises protein-protein and/or protein-DNA interactions required for normal DNMT3C function in vivo. Dnmt3crahu mutant males fail to establish normal methylation within LINE and LTR retrotransposon sequences in the germline and accumulate higher levels of transposon-derived transcripts and proteins, particularly from distinct L1 and ERVK retrotransposon families. Phylogenetic analysis indicates that Dnmt3c arose during rodent evolution by tandem duplication of Dnmt3b, after the divergence of the Dipodoidea and Muroidea superfamilies. These findings provide insight into the evolutionary dynamics and functional specialization of the transposon suppression machinery critical for mammalian sexual reproduction and epigenetic regulation.
2017-08-14 | GSE100959 | GEO
Project description:The KMT2 complex protein ASH2L controls meiosis through silencing transposon
| PRJNA1032460 | ENA
Project description:Transcriptional silencing by heritable cytosine-5 methylation is an ancient strategy to repress transposable elements. It was previously thought that mammals possess four DNA methyltransferase paralogs—Dnmt1, Dnmt3a, Dnmt3b and Dnmt3l—that establish and maintain cytosine-5 methylation. Here we identify a fifth paralog, Dnmt3c, that is essential for retrotransposon methylation and repression in the mouse male germline. From a phenotype-based forward genetics screen, we isolated a mutant mouse called ‘rahu’, which displays severe defects in double-strand-break repair and homologous chromosome synapsis during male meiosis, resulting in sterility. rahu is an allele of a transcription unit (Gm14490, renamed Dnmt3c) that was previously mis-annotated as a Dnmt3-family pseudogene. Dnmt3c encodes a cytosine methyltransferase homolog, and Dnmt3crahu mutants harbor a non-synonymous mutation of a conserved residue within one of its cytosine methyltransferase motifs, similar to a mutation in human DNMT3B observed in patients with immunodeficiency, centromeric instability and facial anomalies syndrome. The rahu mutation lies at a potential dimerization interface and near the potential DNA binding interface, suggesting that it compromises protein-protein and/or protein-DNA interactions required for normal DNMT3C function in vivo. Dnmt3crahu mutant males fail to establish normal methylation within LINE and LTR retrotransposon sequences in the germline and accumulate higher levels of transposon-derived transcripts and proteins, particularly from distinct L1 and ERVK retrotransposon families. Phylogenetic analysis indicates that Dnmt3c arose during rodent evolution by tandem duplication of Dnmt3b, after the divergence of the Dipodoidea and Muroidea superfamilies. These findings provide insight into the evolutionary dynamics and functional specialization of the transposon suppression machinery critical for mammalian sexual reproduction and epigenetic regulation.
2017-08-14 | GSE100958 | GEO