Project description:Mouse heart development arises fromMesp1 expressing cardiovascular progenitors that are specified at the early stage of gastrulation. Lineage tracing and clonal analysisof Mesp1 progenitors revealed that heart development arises from distinct populations of Mesp1+ cardiovascular progenitors (CPs) expressing Mesp1 at different time points during gastrulation that contribute to different heart regions and different cardiovascular lineages. However, it remains unclear what are the molecular mechanisms that control the early regional and lineage segregation of Mesp1 CPs. Here, we performedsingle cell RNA-sequencing of FACS isolated Mesp1 CPs in WT and Mesp1 null embryos at different times to define the cellular and molecular heterogeneity of the Mesp1CPs, identify the role of Mesp1 in regulating cellular heterogeneity and uncover the mechanisms associated with lineage and regional segregation during the early stages of gastrulation.We showed that Mesp1 CPs isolated at E6.75 and E7.25 are molecularly distinct and make the continuum betweenepiblast and later mesodermal cells including hematopoietic progenitors. Single cell transcriptome of Mesp1 deficient CPsshowed that Mesp1 is required for the exitof thepluripotent state and the induction of the cardiovascular gene expression program in vivo.Using dimensional reduction analysis, we identified distinct populations of Mesp1 CPs that correspond to progenitors committed to different celllineages and regions of the heart, identifying the molecular features associated with the early lineage and regional segregation. Notch1CREER lineage tracing, a marker preferentially expressed by one of the different Mesp1CP subpopulations, during the early stage of gastrulation marked almost exclusively ECs, demonstrating theexistence of an early Mesp1 subpopulation committed to the EC fate.This study uncoversthe cellular and molecular heterogeneity associated with early lineage restriction and regional segregation of the heart at the early stage of gastrulation.
Project description:Cardiac development arises from two sources of mesoderm progenitors, the first (FHF) and the second heart field (SHF). Mesp1 has been proposed to mark the most primitive multipotent cardiac progenitors common for both heart fields. Here, using clonal analysis of the earliest prospective cardiovascular progenitors in a temporally controlled manner during the early gastrulation, we found that Mesp1 progenitors consist of two temporally distinct pools of progenitors restricted to either the FHF or the SHF. FHF progenitors were unipotent, while SHF progenitors, were either uni- or bipotent. Microarray and single cell RT-PCR analysis of Mesp1 progenitors revealed the existence of molecularly distinct populations of Mesp1 progenitors, consistent with their lineage and regional contribution. Altogether, these results provide evidence that heart development arises from distinct populations of unipotent and bipotent cardiac progenitors that independently express Mesp1 at different time points during their specification, revealing that the regional segregation and lineage restriction of cardiac progenitors occurs very early during gastrulation. We used microarrays to characterize the molecular mechanisms that control Mesp1 progenitor specification and lineage segregation during the early stage of cardiac mesoderm formation,
Project description:Cardiac development arises from two sources of mesoderm progenitors, the first (FHF) and the second heart field (SHF). Mesp1 has been proposed to mark the most primitive multipotent cardiac progenitors common for both heart fields. Here, using clonal analysis of the earliest prospective cardiovascular progenitors in a temporally controlled manner during the early gastrulation, we found that Mesp1 progenitors consist of two temporally distinct pools of progenitors restricted to either the FHF or the SHF. FHF progenitors were unipotent, while SHF progenitors, were either uni- or bipotent. Microarray and single cell RT-PCR analysis of Mesp1 progenitors revealed the existence of molecularly distinct populations of Mesp1 progenitors, consistent with their lineage and regional contribution. Altogether, these results provide evidence that heart development arises from distinct populations of unipotent and bipotent cardiac progenitors that independently express Mesp1 at different time points during their specification, revealing that the regional segregation and lineage restriction of cardiac progenitors occurs very early during gastrulation. We used microarrays to characterize the molecular mechanisms that control Mesp1 progenitor specification and lineage segregation during the early stage of cardiac mesoderm formation, 50 Mesp1 H2B-GFP+ or Mesp1 H2B-GFP- cells at E6.5 or E7.5 from mouse embryos were sorted for RNA extraction, amplification and hybridization on Affimetrix microarrays. Microaarrays were performed on Mouse Genome 430 PM strip Affymetrix array. The overall design was repeated in two different biological samples.
Project description:Mammalian embryonic development begins with the specification and segregation of the two extra-embryonic lineages, trophectoderm and primitive endoderm, from the pluripotent embryonic lineage, the epiblast. To establish a map of epiblast (EPI) versus primitive endoderm (PrE) lineage segregation which occurs within the inner cell mass (ICM), we comprehensively characterised the gene expression profiles of individual inner cells during blastocyst development. Lineage represents the two embryonic cell lineages: the epiblast (EPI), and the primitive endoderm (PE), which are segregated within the inner cell mass(ICM) during blastocyst development.
Project description:One of the most important topic in mammalian embryogenesis is cell lineage segregation. Briefly, one totipotent zygote will develop into inner cell mass (ICM) and trophectoderm (TE) at blastocyst stage, then the ICM will finally develop into multiple somatic cell lineages and TE will majorly become the placenta tissue which supports and protects the development of the embryo proper. Multiple extrinsic and intrinsic regulatory pathways are involved in facilitating the appropriate development of the embryo. Epigenetic reprogramming is one of the most pervasive events during mouse embryo development(Li, 2002). Recent studies had implied that distinct features for the establishment of DNA methylation(Monk et al., 1987) and histone modifications especially H3K27me3(Liu et al., 2016) during mouse early embryo development. The re-establishment of DNA methylation in early mouse embryos starts at blastocyst stage (about embryonic day 3.5, E3.5) and peaks around the gastrulation stage, while the re-establishment of H3K27me3 exhibits a great level of dynamics and gradually increased CpG preference during pre-implantation embryo development(Liu et al., 2016). However, the underlying epigenetic mechanism concerning the lineage segregation and developmental competence restriction between the pluripotent embryo proper and the supporting extraembryonic tissues especially extraembryonic ectoderm (ExE) remains largely unknown. Surprisingly, no significant difference exists for the distribution of H3K27me3 and DNA methylation between ICM and TE in the preimplantation embryos. Therefore, it is of great importance for unveiling the interplays between H3K27me3 and DNA methylation involving in the restriction of developmental competence between embryonic cells and extraembryonic cells in post-implantation embryos.
Project description:Astrocytes within specific brain regions contribute uniquely to regional circuits for higher-order brain function through interactions with local neurons. The regional diversification of astrocytes is dictated by their embryonic origin, yet the mechanisms governing their regional allocation remain unknown. Here we show that allocation of astrocytes to specific brain regions requires the transcription factor 4 (Tcf4) mediated fate restriction during brain development. Loss of Tcf4 in ventral telencephalic neural progenitors alters the fate of oligodendrocyte precursors to transient intermediate astrocyte precursor cells, resulting in mislocated astrocytes in the dorsal neocortex. These ectopic astrocytes originated from the ventral telencephalon engage with neurons and acquire features reminiscent of local neocortical astrocytes. Furthermore, Tcf4 functions as a suppressor of astrocyte fate during differentiation of oligodendrocyte precursors, thereby restricting the fate to oligodendrocyte lineage. Our study reveals that fate restriction governs regional astrocyte allocation, contributing to astrocyte diversification across brain regions.
Project description:During early development multiple progenitor populations contribute to the formation of the four-chambered heart and its diverse lineages. However, the underlying mechanisms that result in the specification of these progenitor populations are not yet fully understood. We have recently identified a population of cells that gives rise selectively to cardiovascular cells of the heart ventricles. Here, we have used this knowledge to isolate and profile subsets of cardiac mesoderm cells from the mouse embryo and have identified an enrichment for the Notch signaling pathway in ventricular cardiac mesoderm. Using the pluripotent stem cell differentiation system to investigate the role of Notch in a temporally controlled manner, we show that Notch induction increases cardiomyocyte differentiation efficiency. This is due to the enhanced specification of mesoderm to the cardiac lineage. Finally, our data suggests that Notch interacts with WNT signaling to enhance commitment to the cardiac lineage. Overall, our findings support the notion that key signaling events during early heart development are critical for proper lineage specification and segregation and provide additional detail into these processes in mouse and human cardiogenesis.
Project description:During early development multiple progenitor populations contribute to the formation of the four-chambered heart and its diverse lineages. However, the underlying mechanisms that result in the specification of these progenitor populations are not yet fully understood. We have recently identified a population of cells that gives rise selectively to cardiovascular cells of the heart ventricles. Here, we have used this knowledge to isolate and profile subsets of cardiac mesoderm cells from the mouse embryo and have identified an enrichment for the Notch signaling pathway in ventricular cardiac mesoderm. Using the pluripotent stem cell differentiation system to investigate the role of Notch in a temporally controlled manner, we show that Notch induction increases cardiomyocyte differentiation efficiency. This is due to the enhanced specification of mesoderm to the cardiac lineage. Finally, our data suggests that Notch interacts with WNT signaling to enhance commitment to the cardiac lineage. Overall, our findings support the notion that key signaling events during early heart development are critical for proper lineage specification and segregation and provide additional detail into these processes in mouse and human cardiogenesis.