Diverse Routes toward Early Somites in the Mouse Embryo.
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ABSTRACT:
SUBMITTER: Guibentif C
PROVIDER: S-EPMC7808755 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:It is becoming increasingly clear that cells are remarkably sensitive to the biophysical cues of their microenvironment and that these cues play a significant role in influencing their behaviors. In this study, we investigated whether the early pre-implantation embryo is sensitive to mechanical cues, i.e. the elasticity of the culture environment. To test this, we have developed a new embryo culture system where the mechanical properties of the embryonic environment can be precisely defined. The contemporary standard environment for embryo culture is the polystyrene petri dish (PD), which has a stiffness (1 GPa) that is six orders of magnitude greater than the uterine epithelium (1 kPa). To approximate more closely the mechanical aspects of the in vivo uterine environment we used polydimethyl-siloxane (PDMS) or fabricated 3D type I collagen gels (1 kPa stiffness, Col-1k group). Mouse embryo development on alternate substrates was compared to that seen on the petri dish; percent development, hatching frequency, and cell number were observed. Our results indicated that embryos are sensitive to the mechanical environment on which they are cultured. Embryos cultured on Col-1k showed a significantly greater frequency of development to 2-cell (68 ± 15% vs. 59 ± 18%), blastocyst (64 ± 9.1% vs. 50 ± 18%) and hatching blastocyst stages (54 ± 25% vs. 21 ± 16%) and an increase in the number of trophectodermal cell (TE,65 ± 13 vs. 49 ± 12 cells) compared to control embryos cultured in PD (mean ± S.D.; p<.01). Embryos cultured on Col-1k and PD were transferred to recipient females and observed on embryonic day 12.5. Both groups had the same number of fetuses, however the placentas of the Col-1k fetuses were larger than controls, suggesting a continued effect of the preimplantation environment. In summary, characteristics of the preimplantation microenvironment affect pre- and post-implantation growth.
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Project description:It has been generally accepted that the mammalian embryo starts its development with all cells identical, and only when inside and outside cells form do differences between cells first emerge. However, recent findings show that cells in the mouse embryo can differ in their developmental fate and potency as early as the four-cell stage. These differences depend on the orientation and order of the cleavage divisions that generated them. Because epigenetic marks are suggested to be involved in sustaining pluripotency, we considered that such developmental properties might be achieved through epigenetic mechanisms. Here we show that modification of histone H3, through the methylation of specific arginine residues, is correlated with cell fate and potency. Levels of H3 methylation at specific arginine residues are maximal in four-cell blastomeres that will contribute to the inner cell mass (ICM) and polar trophectoderm and undertake full development when combined together in chimaeras. Arginine methylation of H3 is minimal in cells whose progeny contributes more to the mural trophectoderm and that show compromised development when combined in chimaeras. This suggests that higher levels of H3 arginine methylation predispose blastomeres to contribute to the pluripotent cells of the ICM. We confirm this prediction by overexpressing the H3-specific arginine methyltransferase CARM1 in individual blastomeres and show that this directs their progeny to the ICM and results in a dramatic upregulation of Nanog and Sox2. Thus, our results identify specific histone modifications as the earliest known epigenetic marker contributing to development of ICM and show that manipulation of epigenetic information influences cell fate determination.
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Project description:GABAergic interneurons (GABA, ?-aminobutyric acid) regulate neural-circuit activity in the mammalian cerebral cortex. These cortical interneurons are structurally and functionally diverse. Here, we use single-cell transcriptomics to study the origins of this diversity in the mouse. We identify distinct types of progenitor cells and newborn neurons in the ganglionic eminences, the embryonic proliferative regions that give rise to cortical interneurons. These embryonic precursors show temporally and spatially restricted transcriptional patterns that lead to different classes of interneurons in the adult cerebral cortex. Our findings suggest that shortly after the interneurons become postmitotic, their diversity is already patent in their diverse transcriptional programs, which subsequently guide further differentiation in the developing cortex.
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Project description:Assisted reproductive technologies are known to alter the developmental environment of gametes and early embryos during the most dynamic period of establishing the epigenome. This may result in the introduction of errors during active DNA methylation reprogramming. Controlled ovarian hyperstimulation, or superovulation, is a ubiquitously used intervention which has been demonstrated to alter the methylation of certain imprinted genes. The objective of this study was to investigate whether ovarian hyperstimulation results in genome-wide DNA methylation changes in mouse early embryos. Ovarian hyperstimulation was induced by treating mice with either low doses (5 IU) or high doses (10 IU) of PMSG and hCG. Natural mating (NM) control mice received no treatment. Zygotes and 8-cell embryos were collected from each group and DNA methylomes were generated by whole-genome bisulfite sequencing. In the NM group, mean CpG methylation levels slightly decreased from zygote to 8-cell stage, whereas a large decrease in mean CpG methylation level was observed in both superovulated groups. A separate analysis of the mean CpG methylation levels within each developmental stage confirmed that significant genome-wide erasure of CpG methylation from the zygote to 8-cell stage only occurred in the superovulation groups. Our results suggest that superovulation alters the genome-wide DNA methylation erasure process in mouse early pre-implantation embryos. It is not clear whether these changes are transient or persistent. Further studies are ongoing to investigate the impact of ovarian hyperstimulation on DNA methylation re-establishment in later stages of embryo development.
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Project description:Expression profiling of mouse embryos at E2.5, E3.5, E4.25, E4.5, E5.5 E6.0 to identify genes regulated during development of the ICM (inner cell mass), TE (Trophectoderm) and PrE (Primative endoderm) Keywords: development
2008-03-25 | GSE8339 | GEO
Project description:Brusatol, a quassinoid isolated from the fruit of Bruceajavanica, has recently been shown to inhibit nuclear factor erythroid 2-related factor 2 (Nrf2) via Keap1-dependent ubiquitination and proteasomal degradation or protein synthesis. Nrf2 is a transcription factor that regulates the cellular defense response. Most studies have focused on the effects of Nrf2 in tumor development. Here, the critical roles of Nrf2 in mouse early embryonic development were investigated. We found that brusatol treatment at the zygotic stage prevented the early embryo development. Most embryos stayed at the two-cell stage after 5 days of culture (P < 0.05). This effect was associated with the cell cycle arrest, as the mRNA level of CDK1 and cyclin B decreased at the two-cell stage after brusatol treatment. The embryo development potency was partially rescued by the injection of Nrf2 CRISPR activation plasmid. Thus, brusatol inhibited early embryo development by affecting Nrf2-related cell cycle transition from G2 to M phase that is dependent on cyclin B-CDK1 complex.
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Project description:To maintain cell lineage, cells develop a mechanism which can transmit the gene activity information to the daughter cells. In mitosis, TBP (TATA-binding protein), a transcription factor which belongs to TFIID was associated with M phase chromosomes and was proved to be a bookmark for cellular memory. Although previous work showed that TBP was dispensable for mouse oocyte maturation and early embryo development, exogenous TBP protein was detected in the nuclear of oocytes and early embryos. It is still unknown whether exogenous TBP can associate with condensed chromosomes during meiosis and mouse early embryo development. In present study by the injection of GFP-tagged TBP mRNA we for the first time investigated TBP dynamics in mouse early embryos and confirmed its localization pattern in oocytes. The exogenous TBP enriched at germinal vesicle at GV stage but disappeared from the chromosomes after GVBD. Moreover, exogenous TBP was still dispersed from the chromosomes of somatic donor nuclear in oocytes by nuclear transfer (NT), further proving that oocyte has some mechanism to remove TBP. During mouse embryo development, the exogenous TBP was removed from the chromosomes of M phase zygotes, but was found to express weakly at the M phase of 2-cell. Moreover, in the blastocyst TBP was also detected at the M phase chromosomes. Overexpression of TBP caused the failure of oocyte maturation and embryo development. Our results supported the idea that TBP might be a marker for transmitting cellular memory to daughter cells.
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Project description:LINE-1 (L1) retrotransposons are a noted source of genetic diversity and disease in mammals. To expand its genomic footprint, L1 must mobilize in cells that will contribute their genetic material to subsequent generations. Heritable L1 insertions may therefore arise in germ cells and in pluripotent embryonic cells, prior to germline specification, yet the frequency and predominant developmental timing of such events remain unclear. Here, we applied mouse retrotransposon capture sequencing (mRC-seq) and whole-genome sequencing (WGS) to pedigrees of C57BL/6J animals, and uncovered an L1 insertion rate of ≥1 event per eight births. We traced heritable L1 insertions to pluripotent embryonic cells and, strikingly, to early primordial germ cells (PGCs). New L1 insertions bore structural hallmarks of target-site primed reverse transcription (TPRT) and mobilized efficiently in a cultured cell retrotransposition assay. Together, our results highlight the rate and evolutionary impact of heritable L1 retrotransposition and reveal retrotransposition-mediated genomic diversification as a fundamental property of pluripotent embryonic cells in vivo.
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