Abdelbaki, A. | bioRxiv Science

bioRxiv2021

Direct reprogramming of human embryonic to trophoblast stem cells

During the first week of development, human embryos form a blastocyst comprised of an inner cell mass and trophectoderm (TE) cells, the latter of which are progenitors of placental trophoblast. Here we investigated the expression of transcripts in the human TE from early to late blastocyst stages. We identified enrichment of transcription factors GATA2, GATA3, TFAP2C and KLF5 and characterised their protein expression dynamics across TE development. By inducible overexpression and mRNA transfection we determined that these factors, together with MYC, are sufficient to establish induced trophoblast stem cells (iTSCs) from primed human embryonic stem cells. These iTSCs self-renew and recapitulate morphological characteristics, gene expression profiles, and directed differentiation potential similar to existing human TSCs. Systematic omission of each, or combinations of factors, revealed the critical importance of GATA2 and GATA3 for iTSC transdifferentiation. Altogether, these findings provide insights into the transcription factor network that may be operational in the human TE and broaden the methods for establishing cellular models of early human placental progenitor cells, which may be useful in the future to model placental-associated diseases. Summary statementTranscriptional analysis of human blastocysts reveals transcription factors sufficient to derive induced trophoblast stem cells from primed human embryonic stem cells.

developmental biology↗

bioRxiv2019

AURKA destruction is decoupled from its activity at mitotic exit but suppresses interphase activity

Activity of AURKA is controlled through multiple mechanisms including phosphorylation, ubiquitin-mediated degradation, and allosteric interaction with TPX2. Activity peaks at mitosis before AURKA is degraded during mitotic exit in a process strictly dependent on APC/C coactivator FZR1. We used FZR1 knockout cells (FZR1KO) and a novel FRET-based AURKA biosensor to investigate how activity is regulated in absence of destruction. We found that AURKA activity in FZR1KO cells dropped at mitotic exit as rapidly as in parental cells, despite absence of destruction. Unexpectedly, TPX2 was degraded normally in FZR1KO cells. Overexpression of an N-terminal TPX2 fragment sufficient for AURKA binding, but not degraded at mitotic exit, caused delay in AURKA inactivation. We conclude that AURKA inactivation in mitotic exit is determined not by its own degradation but by degradation of TPX2 and therefore dependent on CDC20 rather than FZR1. The biosensor revealed that FZR1 instead suppresses AURKA activity in interphase and is critically required for assembly of the interphase mitochondrial network after mitosis.

cell biology↗