Biology subjects

Betto, R. M.

Publications and source records attributed to Betto, R. M..

3 recordsLinked to original sources

bioRxiv2022

Chemical conversion of human conventional Pluripotent Stem Cells to Trophoblast Stem Cells

In human embryos, naive pluripotent cells of the inner cell mass generate epiblast, primitive endoderm and Trophectoderm (TE) lineage, whence trophoblast cells derive. In vitro, naive pluripotent stem cells (PSCs) retain this potential and can generate trophoblast stem cells (TSCs), while conventional PSCs form amnion-like cells and lack the competence to generate TSCs. Transient histone deacetylase and MEK inhibitions with LIF stimulation can be used to chemically reset conventional to naive PSCs. Here we report that chemical resetting induced expression of both naive and TSC markers and of placental imprinted genes. A modified chemical resetting protocol allowed for the fast and efficient conversion of conventional PSCs into TSCs, entailing shutdown of pluripotency genes and full activation of the trophoblast master regulators, without induction of amnion markers. Chemical resetting generates a responsive intermediate state, in which conventional PSCs rapidly acquire competence to form TSCs without the need of stabilisation and expansion in a naive state. The efficiency and rapidity of our system will be useful for the study of cell fate transitions, and to generate models of placental disorders.

developmental biology↗

bioRxiv2021

STAT3 and HIF1α cooperatively mediate the transcriptional and physiological responses to hypoxia

STAT3 and HIF1 are two fundamental transcription factors involved in many merging processes, like angiogenesis, metabolism, and cell differentiation. Notably, under pathological conditions, the two factors have been shown to interact genetically, but both the molecular mechanisms underlying such interactions and their relevance under physiological conditions remain unclear. Here we report that STAT3 is required for the HIF1-dependent response to hypoxia. In Stat3 knock-out pluripotent embryonic stem cells (ESCs), a large fraction of HIF1 target genes is not induced by hypoxia. Mechanistically, STAT3 does not regulate neither HIF1 expression nor stability, rather, it physically interacts with it in the nucleus. In vivo, we observed that both genetic and chemical inactivation of Stat3 blunted physiological responses to hypoxia, such as angiogenesis, erythropoiesis, and immune cell mobilization. Such defects were accompanied with faulty transcriptional activity of HIF1. In sum, our data reveal that STAT3 and HIF1 cooperatively mediate the physiological response to hypoxia.

developmental biology↗

bioRxiv2020

Mitochondrial STAT3 regulates proliferation of tissue stem cells.

The STAT3 transcription factor, acting both in the nucleus and mitochondria, maintains embryonic stem cell pluripotency and promotes their proliferation. In this work, using zebrafish, we determined in vivo that mitochondrial STAT3 regulates mtDNA transcription in embryonic and larval stem cell niches and that this activity affects their proliferation rates. As a result, we demonstrated that STAT3 import inside mitochondria requires Y705 phosphorylation by Jak2, while its mitochondrial transcriptional activity, as well as its effect on proliferation, depends on the MAPK target S727. These data were confirmed using mouse embryonic stem cells: Y705 mutated STAT3 cannot enter the mitochondrion while the S727 mutation does not affect mitochondrial import of the protein. Surprisingly, STAT3-dependent increase of mitochondrial transcription seems independent from STAT3 binding to STAT3 responsive elements. Finally, loss of function experiments, with chemical inhibition of JAK/STAT3 pathway or genetic ablation of stat3 gene, demonstrated that STAT3 is also required for cell proliferation in the intestine of zebrafish.

developmental biology↗