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Anastassiadis, K.

Publications and source records attributed to Anastassiadis, K..

2 recordsLinked to original sources

Human axial progenitors generate trunk neural crest cells

The neural crest (NC) is a multipotent embryonic cell population generating distinct cell types in an axial position-dependent manner. The production of NC cells from human pluripotent stem cells (hPSCs) is a valuable approach to study human NC biology. However, the origin of human trunk NC remains undefined and therefore current in vitro differentiation strategies induce only a modest yield of trunk NC cells. Here we show that hPSC-derived axial progenitors, the posteriorly-located drivers of embryonic axis elongation, give rise to trunk NC cells and their derivatives. Moreover, we define the molecular signatures associated with the emergence of human NC cells of distinct axial identities in vitro. Collectively, our findings indicate that there are two routes toward a human post-cranial NC state: the birth of cardiac and vagal NC is facilitated by retinoic acid-induced posteriorisation of an anterior precursor whereas trunk NC arises within a pool of posterior axial progenitors.

developmental biology

Differential epigenetic landscapes and transcription factors explain X-linked gene behaviours during X-chromosome reactivation in the mouse inner cell mass

X-chromosome inactivation (XCI) is established in two waves during mouse development. First, silencing of the paternal X chromosome (Xp) is triggered, with transcriptional repression of most genes and enrichment of epigenetic marks such as H3K27me3 being achieved in all cells by the early blastocyst stage. XCI is then reversed in the inner cell mass (ICM), followed by a second wave of maternal or paternal XCI, in the embryo-proper. Although the role of Xist RNA in triggering XCI is now clear, the mechanisms underlying Xp reactivation in the inner cell mass have remained enigmatic. Here we use in vivo single cell approaches (allele-specific RNAseq, nascent RNA FISH and immunofluorescence) and find that different genes show very different timing of reactivation. We observe that the genes reactivate at different stages and that initial enrichment in H3K27me3 anti-correlates with the speed of reactivation. To define whether this repressive histone mark is lost actively or passively, we investigate embryos mutant for the X-encoded H3K27me3 demethylase, UTX. Xp genes that normally reactivate slowly are retarded in their reactivation in Utx mutants, while those that reactive rapidly are unaffected. Therefore, efficient reprogramming of some X-linked genes in the inner cell mass is very rapid, indicating minimal epigenetic memory and potentially driven by transcription factors, whereas others may require active erasure of chromatin marks such as H3K27me3.

developmental biology