in-vitro-selection-engineered-transcriptional-repressors-for-targeted

<em>In Vitro</em> Selection of Engineered Transcriptional Repressors for Targeted Epigenetic Silencing

Gene inactivation is instrumental to study gene function and represents a promising strategy for the treatment of a broad range of diseases. Among ...

IRCCS San Raffaele Scientific Institute

Lamin A is a component of the inner nuclear membrane that, together with epigenetic factors, organizes the genome in higher order structures required for transcriptional control. Mutations in the lamin A/C gene cause several diseases belonging to the class of laminopathies, including muscular dystrophies. Nevertheless, molecular mechanisms involved in the pathogenesis of lamin A-dependent dystrophies are still largely unknown. The polycomb group (PcG) of proteins are epigenetic repressors and lamin A interactors, primarily involved in the maintenance of cell identity. Using a murine model of Emery-Dreifuss muscular dystrophy (EDMD), we show here that lamin A loss deregulated PcG positioning in muscle satellite stem cells, leading to derepression of non-muscle-specific genes and p16INK4a, a senescence driver encoded in the Cdkn2a locus. This aberrant transcriptional program caused impairment in self-renewal, loss of cell identity, and premature exhaustion of the quiescent satellite cell pool. Genetic ablation of the Cdkn2a locus restored muscle stem cell properties in lamin A/C-null dystrophic mice. Our findings establish a direct link between lamin A and PcG epigenetic silencing and indicate that lamin A-dependent muscular dystrophy can be ascribed to intrinsic epigenetic dysfunctions of muscle stem cells.

Dysfunctional polycomb transcriptional repression contributes to lamin A/C-dependent muscular dystrophy.

The generation of haematopoietic stem cells (HSCs) from human pluripotent stem cells (hPSCs) is a major goal for regenerative medicine. During embryonic development, HSCs derive from haemogenic endothelium (HE) in a NOTCH- and retinoic acid (RA)-dependent manner. Although a WNT-dependent (WNTd) patterning of nascent hPSC mesoderm specifies clonally multipotent intra-embryonic-like HOXA definitive HE, this HE is functionally unresponsive to RA. Here we show that WNTd mesoderm, before HE specification, is actually composed of two distinct KDR CD34 populations. CXCR4CYP26A1 mesoderm gives rise to HOXA multilineage definitive HE in an RA-independent manner, whereas CXCR4 ALDH1A2 mesoderm gives rise to HOXA multilineage definitive HE in a stage-specific, RA-dependent manner. Furthermore, both RA-independent (RAi) and RA-dependent (RAd) HE harbour transcriptional similarity to distinct populations found in the early human embryo, including HSC-competent HE. This revised model of human haematopoietic development provides essential resolution to the regulation and origins of the multiple waves of haematopoiesis. These insights provide the basis for the generation of specific haematopoietic populations, including the de novo specification of HSCs.

Article	Year
Dysfunctional polycomb transcriptional repression contributes to lamin A/C-dependent muscular dystrophy. The Journal of clinical investigation\| PubMed ID: 31999646	2020
Identification of a retinoic acid-dependent haemogenic endothelial progenitor from human pluripotent stem cells. Nature cell biology\| PubMed ID: 35484246	2022

Sara Valsoni

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