Project description:Embryonic development is largely conserved among mammals. However, certain genes show divergent functions. By generating a transcriptional atlas containing >30,000 cells from post-implantation non-human primate embryos, we uncover that ISL1, a gene with a well-established role in cardiogenesis, controls a gene regulatory network in primate amnion. CRISPR/Cas9-targeting of ISL1 results in non-human primate embryos which do not yield viable offspring, demonstrating that ISL1 is critically required in primate embryogenesis. On a cellular level, mutant ISL1 embryos display a failure in mesoderm formation due to reduced BMP4 signaling from the amnion. Via loss of function and rescue studies in human embryonic stem cells we confirm a similar role of ISL1 in human in vitro derived amnion. This study highlights the importance of the amnion as a signaling center during primate mesoderm formation and demonstrates the potential of in vitro primate model systems to dissect the genetics of early human embryonic development.
Project description:The germ cell lineage ensures reproduction, heredity and evolution. However, the mechanism for germ cell specification in primates, including humans, has been unknown. In primates, the pluripotent epiblast segregates the amnion upon implantation and thereafter initiates gastrulation to generate three germ layers. Here, we show that in cynomolgus monkeys, the SOX17/BLIMP1/TFAP2C-positive primordial germ cells (cyPGCs) arise from the dorsal amnion at embryonic day (E) 11. cyPGCs then migrate down beneath the epiblast and expand their numbers, through proliferation and continuous recruitment from the posterior amnion, around posterior yolk sac endoderm by E17. Remarkably, the amnion itself expresses BMP4, a cytokine potentially critical for PGC specification, thereby inducing cyPGCs in an autocrine fashion. Consistently, the amnion expresses T, a key mesodermal factor, prior to the onset of gastrulation. Our study demonstrates the origin of cyPGCs in the amnion, which undergoes a unique morphogenetic event prior to and independent from the gastrulation.
Project description:Mice deficient in the BMP-effector, Smad5 (Smad5 KO), develop severe defects in embryonic morphogenesis as well as a delay in amnion-chorion separation, important extraembryonic tissues. After closure of the proamniotic canal, a remarkable ectopic primitive streak-like aggregate develops in the amnion of these mutants. We investigated the earliest steps of mutant amnion misdifferentiation by RNAseq of single Control (Ctrl) and Smad5 KO amnion samples collected before the appearance of the aggregate. The transcriptome analysis revealed two separate sets of non-squamous amnion defects. One set of mutants (KO-SetA) robustly overexpressed streak mesoderm-related genes conform former analyses (Pereira et al., 2012). The other set overexpressed extraembryonic ectoderm markers suggestive of chorionic inclusion in amnion (KO-SetB). Tetraploid chimera analyses confirmed that SMAD5 deficiency in the epiblast can result in two distinct sets of amnion defects: one with impaired anterior amnion expansion and differentiation, and another with inclusion of chorionic extraembryonic ectoderm in the space normally occupied by amnion.
Project description:Cellular differentiation and lineage commitment are considered to be robust and irreversible processes during development. Recent work has shown that mouse and human fibroblasts can be reprogrammed to a pluripotent state with a combination of four transcription factors. This raised the question of whether transcription factors could directly specify somatic cell fates in cells such as pancreatic ? cells, contractile cardiomyocytes and neurons. We hypothesized that combinatorial expression of chondrocyte-specific transcription factors could directly convert human amnion cells into chondrosarcoma. Starting from a pool of candidate genes, we identified a combination of only five genes (5F pool), BCL6, T (also called BRACHYURY), c-MYC, MITF and BAF60C (also called SMARCD3) that rapidly and efficiently convert postnatal human amnion into chondrosarcoma. The cells generated expressed multiple cartilage-specific genes such as collagen type II ?1, link protein-1 and aggrecan, and exhibited characteristics of cartilage both in vivo and in vitro. Expression of the endogenous genes for T and MITF was initiated, implying that the cell conversion is due to not only the forced expression of the transgenes, but also the cellular reprogramming by the transgenes. The same set of genes converted human placental artery-derived endothelial (hPAE) cells and menstrual blood-derived cells into chondrosarcoma cells, implying that this conversion is independent of cell types. Direct conversion system from non-cartilage tissue to cartilaginous tissue contributes substantially to a major advance toward cartilage development, oncogenesis of chondrocytes, and cell-based therapy. We hypothesized that combinatorial expression of chondrocyte-specific transcription factors could directly convert human amnion cells into chondrosarcoma. Starting from a pool of candidate genes, we identified a combination of only five genes that rapidly efficiently convert postnatal human amnion into chondrosarcoma.
Project description:Analysis of cultured human amnion mesenchymal cells treated with synthetic glucocorticoid dexamethasone for 48 hours. Results provide insight into the molecular response of the human amnion to glucocorticoids.
Project description:We encapsulated common marmoset pluripotent stem cells (cmPSCs) in agarose microgels and optimised culture conditions to generate epiblast and amnion spheroids. Using this system, we investigate the effects of signalling perturbations on epiblast and amnion spheroids as a model for early lineage specification