Project description:During the development of the vertebrate embryo, segmented structures called somites are periodically formed from the presomitic mesoderm (PSM), and give rise to the vertebral column. While somite formation has been studied in several animal models, it is less clear how well this process is conserved in humans. Recent progress has made it possible to study aspects of human paraxial mesoderm development such as the human segmentation clock in vitro using human pluripotent stem cells (hPSCs), however, somite formation has not been observed in these monolayer cultures. Here, we describe the generation of human paraxial mesoderm (PM) organoids from hPSCs (termed Somitoids), which recapitulate the molecular, morphological and functional features of paraxial mesoderm development, including formation of somite-like structures in vitro. Using a quantitative image-based screen, we identify critical parameters such as initial cell number and signaling modulations that reproducibly yielded somite formation in our organoid system. In addition, using single-cell RNA sequencing and 3D imaging, we show that PM organoids both transcriptionally and morphologically resemble their in vivo counterparts and can be differentiated into somite derivatives. Our organoid system is reproducible and scalable, allowing for the systematic and quantitative analysis of human spinal cord development and disease in vitro.
Project description:The trunk axial skeleton develops from paraxial mesoderm cells. Our recent study demonstrated that conditional knockout of the stem cell factor Sall4 in mice by TCre caused tail truncation and a disorganized axial skeleton posterior to the lumbar level. Based on this phenotype, we hypothesized that, in addition to the previously reported role of Sall4 in neuromesodermal progenitors, Sall4 is involved in the development of the paraxial mesoderm tissue. ATAC-seq in TCre; Sall4 mutant posterior trunk mesoderm shows that Sall4 knockout reduces chromatin accessibility. We found that Sall4- dependent open chromatin status drives activation and repression of WNT signaling activators and repressors, respectively, to promote WNT signaling. Moreover, footprinting analysis of ATAC-seq data suggests that Sall4-dependent chromatin accessibility facilitates CTCF binding, which contributes to the repression of neural genes within the mesoderm. This study unveils multiple mechanisms by which Sall4 regulates paraxial mesoderm development by directing activation of mesodermal genes and repression of neural genes.
Project description:Laser capture microdissection (LCM) was used to isolate cells from the principal critical micro-regions, whose development, differentiation and signaling interactions are responsible for the construction of the mammalian face. At E8.5, as migrating neural crest cells begin to exit the neural fold/epidermal ectoderm boundary, we examined the facial mesenchyme, composed of neural crest and paraxial mesoderm cells, as well as cells from adjacent neuroepithelium We performed single cell studies to better define the gene expression states of the early E8.5 pioneer neural crest cells and paraxial mesoderm, and present microarray data detailing expression patterns within these embryonic cell populations. Mouse emrbyos were harvested at developmental stage E8.5 and single cells were captured from the neuroepithilium, neural crest, and paraxial mesoderm. RNA was extracted, labelled, and quantified using the Mouse ST-l microarray.
Project description:During mammalian embryogenesis, axial elongation of the neural tube is critical for establishing the anterior-posterior body axis, but is difficult to interrogate directly because it occurs post-implantation. Here we report an organoid model of neural tube extension using human pluripotent stem cell (hPSC) aggregates that recapitulates the morphologic and temporal gene expression patterns of neural tube development. Axially extending organoids consisted of longitudinally elongated epithelial compartments and contained TBXT(+)SOX2(+) neuromesodermal progenitors, PAX6(+) Nestin(+) neural progenitor populations, and MEOX1(+) paraxial mesoderm populations. Wnt agonism stimulated axial extensions in a dose-dependent manner and elongated organoids displayed regionalized rostral-caudal HOX gene expression, with hindbrain (HOXB1) expression distinct from brachial (HOXC6) and thoracic (HOXB9) expression. CRISPR interference-mediated silencing of BMP inhibitors induced elongation phenotypes that mimicked murine knockout models, and knock-down of the downstream Wnt target, TBXT, increased neuroepithelial compartmentalization and resulted in multiple extensions. These results indicate the potent morphogenic capacity of hPSC organoids to undergo axial elongation in a manner that can be used to dissect the cellular organization and patterning decisions that dictate early human nervous system development.
Project description:During mammalian embryogenesis, axial elongation of the neural tube is critical for establishing the anterior-posterior body axis, but is difficult to interrogate directly because it occurs post-implantation. Here we report an organoid model of neural tube extension using human pluripotent stem cell (hPSC) aggregates that recapitulates the morphologic and temporal gene expression patterns of neural tube development. Axially extending organoids consisted of longitudinally elongated epithelial compartments and contained TBXT(+)SOX2(+) neuromesodermal progenitors, PAX6(+) Nestin(+) neural progenitor populations, and MEOX1(+) paraxial mesoderm populations. Wnt agonism stimulated axial extensions in a dose-dependent manner and elongated organoids displayed regionalized rostral-caudal HOX gene expression, with hindbrain (HOXB1) expression distinct from brachial (HOXC6) and thoracic (HOXB9) expression. CRISPR interference-mediated silencing of BMP inhibitors induced elongation phenotypes that mimicked murine knockout models, and knock-down of the downstream Wnt target, TBXT, increased neuroepithelial compartmentalization and resulted in multiple extensions. These results indicate the potent morphogenic capacity of hPSC organoids to undergo axial elongation in a manner that can be used to dissect the cellular organization and patterning decisions that dictate early human nervous system development.
Project description:TWIST1, a basic helix-loop-helix transcription factor is essential for the development of cranial mesoderm and cranial neural crest-derived craniofacial structures. Our previous work showed that, in the absence of TWIST1, some cells within the cranial mesoderm adopt an abnormal epithelial configuration. Here, we show by transcriptome analysis that loss of TWIST1 in the cranial mesoderm is accompanied by a reduction in the expression of genes that are associated with cell-extracellular matrix interactions and the acquisition of mesenchymal characteristics. By comparing the transcriptional profiles of cranial mesoderm-specific Twist1 loss-of-function mutant and control mouse embryos, we identified a set of genes that are both TWIST1-dependent and predominantly expressed in the mesoderm. By ChIP-seq in a cell line model of a TWIST1-dependent mesenchymal state, we identified, among the downstream genes, three direct transcriptional targets of TWIST1: Ddr2, Pcolce and Tgfbi. Our findings show that the mesenchymal properties of the cranial mesoderm is likely to be regulated by a network of TWIST1 targets genes that influence the extracellular matrix and cell-matrix interactions, and collectively they are required for the morphogenesis of the craniofacial structures. For microarray analysis of CM-CKO embryos, embryo heads of four genotypes were collected at E8.5 (5-7 somites) and E9.5 (18- 20 somites): CM-CKO (Twist1flox/del; Mesp1Cre/+), CM-Het (Twist1flox/wt; Mesp1Cre/+), Het (Twist1flox/del; Mesp1+/+) and Control (Twist1flox/wt; Mesp1+/+). Sample sizes for E8.5 embryos were as follows: Control, n=4 CM-CKO, n=4; Het, n=3; CM-Hets, n=3).
Project description:To examine global gene expression profile of chicken early paraxial mesoderm differentiation, we microdissected stage 12HH chicken PSM regions into 20 pieces (10 pieces both left-right PSM), including the tail bud, the PSM and somites. We create microarray series using these fragments.
Project description:Somites form during embryonic development and give rise to unique cell and tissue types, such as skeletal muscles and bones and cartilages of the vertebrae. Using somitogenesis stage human embryos, we performed the first ever transcriptomic profiling of human presomitic mesoderm as well as nascent and developed somites. Using this approach we uncovered novel regulators unique duing human somitogensis, and efficiently guided human pluripotent stem cells to differentiate to somite cells and downstream progeny. This work improves our understanding of human somite development and may enhance our ability to model and treat diseases affecting somite derivatives.
Project description:TWIST1, a basic helix-loop-helix transcription factor is essential for the development of cranial mesoderm and cranial neural crest-derived craniofacial structures. Our previous work showed that, in the absence of TWIST1, some cells within the cranial mesoderm adopt an abnormal epithelial configuration. Here, we show by transcriptome analysis that loss of TWIST1 in the cranial mesoderm is accompanied by a reduction in the expression of genes that are associated with cell-extracellular matrix interactions and the acquisition of mesenchymal characteristics. By comparing the transcriptional profiles of cranial mesoderm-specific Twist1 loss-of-function mutant and control mouse embryos, we identified a set of genes that are both TWIST1-dependent and predominantly expressed in the mesoderm. By ChIP-seq in a cell line model of a TWIST1-dependent mesenchymal state, we identified, among the downstream genes, three direct transcriptional targets of TWIST1: Ddr2, Pcolce and Tgfbi. Our findings show that the mesenchymal properties of the cranial mesoderm is likely to be regulated by a network of TWIST1 targets genes that influence the extracellular matrix and cell-matrix interactions, and collectively they are required for the morphogenesis of the craniofacial structures. For microarray analysis of CM-CKO embryos, embryo heads of four genotypes were collected at E8.5 (5-7 somites) and E9.5 (18- 20 somites): CM-CKO (Twist1flox/del; Mesp1Cre/+), CM-Het (Twist1flox/wt; Mesp1Cre/+), Het (Twist1flox/del; Mesp1+/+) and Control (Twist1flox/wt; Mesp1+/+). Sample sizes for E9.5 were as follows: Control, n=3; CM-CKO, n=4; Het, n=4; CM-Het, n=4). RNA was extracted using the RNeasy Micro kit (Qiagen) and samples sent to the Australian Genome Research Foundation for labelling and hybridization.