Biology subjects

Azami, T.

Publications and source records attributed to Azami, T..

3 recordsLinked to original sources

bioRxiv2023

A single-cell atlas of pig gastrulation as a resource for comparative embryology

Early mammalian gastrulations cell-fate decisions are poorly understood due to difficulties obtaining non-rodent embryos. The bilaminar disc of pig embryos mirrors humans, making them a useful proxy for studying gastrulation. Here we present a single-cell transcriptomic atlas of pig gastrulation, revealing cell-fate emergence dynamics, as well as conserved and divergent gene programs governing early porcine, primate, and murine development. We highlight heterochronicity in extraembryonic cell-type development, despite the broad conservation of cell-type-specific transcriptional programs. We apply these findings in combination with functional investigations, to outline conserved spatial, molecular, and temporal events during definitive endoderm (DE). We find early FOXA2+/TBXT-embryonic disc cells directly from DE, contrasting later-emerging FOXA2/TBXT+ node/notochord progenitors. Unlike mesoderm, none of these progenitors undergo epithelial-to-mesenchymal transition. DE/Node fate hinges on balanced WNT and hypoblast-derived NODAL, which is extinguished upon DE differentiation. These findings emphasise the interplay between temporal and topological signalling in early fate decisions during gastrulation.

developmental biology↗

bioRxiv2022

Requirement for STAT3 and its target, TFCP2L1 in self-renewal of naïve pluripotent stem cells in vivo and in vitro

We previously demonstrated gradual loss of epiblast during diapause in embryos lacking components of the LIF/IL6 receptor. Here we explore requirement for the downstream signalling transducer and activator of transcription, STAT3 and its target, TFCP2L1, in maintenance of naive pluripotency. Unlike conventional markers, such as NANOG, which remains high in epiblast until implantation, both STAT3 and TFCP2L1 proteins decline during blastocyst expansion, but intensify in the embryonic region after induction of diapause, as observed visually and confirmed using our novel image analysis tool, consistent with our previous transcriptional expression data. Embryos lacking STAT3 or TFCP2L1, underwent catastrophic loss of most of the inner cell mass during the first few days of diapause, implicating involvement of signals in addition to LIF/IL6 for sustaining naive pluripotency in vivo. By blocking MEK/ERK signalling from the morula stage we could derive embryonic stem cells with high efficiency from STAT3 null embryos, but not those lacking TFCP2L1, suggesting a hitherto unknown additional role for this essential STAT3 target in transition from embryo to embryonic stem cells in vitro. Summary StatementInducing diapause in mouse embryos demonstrates that STAT3 and TFCP2L1 are essential for self-renewal of the epiblast, but only TFCP2L1 is required for derivation of embryonic stem cells.

developmental biology↗

bioRxiv2022

Distinct phospho-variants of STAT3 regulate naïve pluripotency and developmental pace in vivo

STAT3 has been studied extensively in the context of self-renewal of naive pluripotent mouse embryonic stem cells. We uncovered acute roles for STAT3 and its target, TFCP2L1, in maintenance of epiblast and primitive endoderm during in vivo diapause. On an outbred genetic background, we observed consistent developmental retardation from implantation until embryonic day 11.5, beginning with significant reduction of epiblast cells at implantation in Stat3 null embryos. Remarkably, mutants closely resemble non-affected embryos from the previous day at all postimplantation stages examined. We attribute this phenotype to loss of the active serine phosphorylated form of STAT3 required for neural differentiation and implicated in growth defects in mice and humans. Bulk RNA-sequencing analysis of isolated epiblasts revealed compromised lipid metabolism in Stat3 null embryos by embryonic day 6.5. Furthermore, we demonstrate that gastruloids generated from Stat3 null ESCs failed to extend the posterior axis or maintain BRACHYURY expression and were underrepresented in this region when mixed with wild type cells in chimaeric gastruloids. Our study implicates a role for STAT3 in temporal control of embryonic progression and metabolic mechanisms.

developmental biology↗