Sequential formation and resolution of multiple rosettes drive embryo remodelling after implantation

The morphogenetic remodelling of embryo architecture after implantation culminates in pro-amniotic cavity formation. Despite its key importance, how this transformation occurs remains unknown. Here, we apply high-resolution imaging of embryos developing in vivo and in vitro, spatial RNA sequencing and 3D trophoblast stem cell models to determine the sequence and mechanisms of these remodelling events. We show that cavitation of the embryonic tissue is followed by folding of extra-embryonic tissue to mediate the formation of a second extra-embryonic cavity. Concomitantly, at the boundary between embryonic and extra-embryonic tissues, a hybrid 3D rosette forms. Resolution of this rosette enables the embryonic cavity to invade the extra-embryonic tissue. Subsequently, β1-integrin signalling mediates the formation of multiple extra-embryonic 3D rosettes. Podocalyxin exocytosis leads to their polarized resolution, permitting the extension of embryonic and extra-embryonic cavities and their fusion into a unified pro-amniotic cavity. These morphogenetic transformations of embryogenesis reveal a previously unappreciated mechanism for lumen expansion and fusion

ESC-Derived Basal Forebrain Cholinergic Neurons Ameliorate the Cognitive Symptoms Associated with Alzheimer’s Disease in Mouse Models

SummaryDegeneration of basal forebrain cholinergic neurons (BFCNs) is associated with cognitive impairments of Alzheimer’s disease (AD), implying that BFCNs hold potentials in exploring stem cell-based replacement therapy for AD. However, studies on derivation of BFCNs from embryonic stem cells (ESCs) are limited, and the application of ESC-derived BFCNs remains to be determined. Here, we report on differentiation approaches for directing both mouse and human ESCs into mature BFCNs. These ESC-derived BFCNs exhibit features similar to those of their in vivo counterparts and acquire appropriate functional properties. After transplantation into the basal forebrain of AD model mice, ESC-derived BFCN progenitors predominantly differentiate into mature cholinergic neurons that functionally integrate into the endogenous basal forebrain cholinergic projection system. The AD mice grafted with mouse or human BFCNs exhibit improvements in learning and memory performances. Our findings suggest a promising perspective of ESC-derived BFCNs in the development of stem cell-based therapies for treatment of AD

Self-assembly of embryonic and two extra-embryonic stem cell types into gastrulating embryo-like structures.

Embryonic stem cells can be incorporated into the developing embryo and its germ line, but, when cultured alone, their ability to generate embryonic structures is restricted. They can interact with trophoblast stem cells to generate structures that break symmetry and specify mesoderm, but their development is limited as the epithelial-mesenchymal transition of gastrulation cannot occur. Here, we describe a system that allows assembly of mouse embryonic, trophoblast and extra-embryonic endoderm stem cells into structures that acquire the embryo's architecture with all distinct embryonic and extra-embryonic compartments. Strikingly, such embryo-like structures develop to undertake the epithelial-mesenchymal transition, leading to mesoderm and then definitive endoderm specification. Spatial transcriptomic analyses demonstrate that these morphological transformations are underpinned by gene expression patterns characteristic of gastrulating embryos. This demonstrates the remarkable ability of three stem cell types to self-assemble in vitro into gastrulating embryo-like structures undertaking spatio-temporal events of the gastrulating mammalian embryo.European Research Council (669198) Wellcome Trust (098287/Z/12/Z)

Self-assembly of embryonic and two extra-embryonic stem cell types into gastrulating embryo-like structures

Embryonic stem cells can be incorporated into the developing embryo and its germ line, but, when cultured alone, their ability to generate embryonic structures is restricted. They can interact with trophoblast stem cells to generate structures that break symmetry and specify mesoderm, but their development is limited as the epithelial–mesenchymal transition of gastrulation cannot occur. Here, we describe a system that allows assembly of mouse embryonic, trophoblast and extra-embryonic endoderm stem cells into structures that acquire the embryo’s architecture with all distinct embryonic and extra-embryonic compartments. Strikingly, such embryo-like structures develop to undertake the epithelial–mesenchymal transition, leading to mesoderm and then definitive endoderm specification. Spatial transcriptomic analyses demonstrate that these morphological transformations are underpinned by gene expression patterns characteristic of gastrulating embryos. This demonstrates the remarkable ability of three stem cell types to self-assemble in vitro into gastrulating embryo-like structures undertaking spatio-temporal events of the gastrulating mammalian embryo

Sequential formation and resolution of multiple rosettes drive embryo remodelling after implantation

The morphogenetic remodelling of embryo architecture after implantation culminates in pro-amniotic cavity formation. Despite its key importance, how this transformation occurs remains unknown. Here, we apply high-resolution imaging of embryos developing in vivo and in vitro, spatial RNA sequencing and 3D trophoblast stem cell models to determine the sequence and mechanisms of these remodelling events. We show that cavitation of the embryonic tissue is followed by folding of extra-embryonic tissue to mediate the formation of a second extra-embryonic cavity. Concomitantly, at the boundary between embryonic and extra-embryonic tissues, a hybrid 3D rosette forms. Resolution of this rosette enables the embryonic cavity to invade the extra-embryonic tissue. Subsequently, β1-integrin signalling mediates the formation of multiple extra-embryonic 3D rosettes. Podocalyxin exocytosis leads to their polarized resolution, permitting the extension of embryonic and extra-embryonic cavities and their fusion into a unified pro-amniotic cavity. These morphogenetic transformations of embryogenesis reveal a previously unappreciated mechanism for lumen expansion and fusionThe M.Z.G lab is supported by grants from the European Research Council (669198) and the Welcome Trust (098287/Z/12/Z) and the EU Horizon 2020 Marie Sklodowska-Curie actions (ImageInLife,721537). C.K is supported by BBSRC Doctoral training studentship

Pluripotent Stem Cell Studies Elucidate the Underlying Mechanisms of Early Embryonic Development

Early embryonic development is a multi-step process that is intensively regulated by various signaling pathways. Because of the complexity of the embryo and the interactions between the germ layers, it is very difficult to fully understand how these signals regulate embryo patterning. Recently, pluripotent stem cell lines derived from different developmental stages have provided an in vitro system for investigating molecular mechanisms regulating cell fate decisions. In this review, we summarize the major functions of the BMP, FGF, Nodal and Wnt signaling pathways, which have well-established roles in vertebrate embryogenesis. Then, we highlight recent studies in pluripotent stem cells that have revealed the stage-specific roles of BMP，FGF and Nodal pathways during neural differentiation. These findings enhance our understanding of the stepwise regulation of embryo patterning by particular signaling pathways and provide new insight into the mechanisms underlying early embryonic development

Gain-of-function mutations in Trim71 linked to congenital hydrocephalus.

The genetic basis of congenital hydrocephalus is only partially understood. A new study in PLOS Biology reports a potential gain-of-function pathological mechanism of congenital hydrocephalus in mouse embryonic stem cells that involves Wnt-β-catenin signaling pathway regulation

Genome-wide analysis of histone acetylation dynamics during mouse embryonic stem cell neural differentiation

Epigenetic modification as an intrinsic fine-tune program cooperates with key transcription factors to regulate the cell fate determination. The histone acetylation participating in neural differentiation of pluripotent stem cells is expected but not well studied. Here, using acetylated histone H3 ChIP-sequencing (ChIP-seq), we demonstrate that the histone H3 acetylation level is gradually increased on the neural gene loci while decreased on the neural-inhibitory gene loci during mouse embryonic stem cell (mESC) neural differentiation. We further show that histone deacetylase 1 (HDAC1) is essential for neural commitment by targeting Nodal signaling. Thus, our study reveals a mechanism by which the epigenetic modification of histone acetylation/deacetylation interacts with extracellular signaling in mESC neural fate determination. Data were deposited in Gene Expression Omnibus (GEO) datasets under reference number GSE66025

Integration of Computational Analysis and Spatial Transcriptomics in Single-cell Studies

Recent advances of single-cell transcriptomics technologies and allied computational methodologies have revolutionized molecular cell biology. Meanwhile, pioneering explorations in spatial transcriptomics have opened up avenues to address fundamental biological questions in health and diseases. Here, we review the technical attributes of single-cell RNA sequencing and spatial transcriptomics, and the core concepts of computational data analysis. We further highlight the challenges in the application of data integration methodologies and the interpretation of the biological context of the findings