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Within the vasculature, specialized cellular extensions from endothelium (and sometimes smooth muscle) protrude through the extracellular matrix where they interact with the opposing cell type. These structures, termed myoendothelial junctions, have been cited as a possible key element in the control of several vascular physiologies and pathologies. This review will discuss observations that have led to a focus on the myoendothelial junction as a cellular integration point in the vasculature for both homeostatic and pathological conditions and as a possible independent signaling entity. We will also highlight the need for novel approaches to studying the myoendothelial junction in order to comprehend the cellular biology associated with this structure. [ABSTRACT FROM AUTHOR]

Epigenetic mechanisms contribute to the regulation of cell differentiation and function. Vascular smooth muscle cells (SMCs) are specialized contractile cells that retain phenotypic plasticity even after differentiation. Here, by performing selective demethylation of histone H3 lysine 4 di-methylation (H3K4me2) at SMC-specific genes, we uncovered that H3K4me2 governs SMC lineage identity. Removal of H3K4me2 via selective editing in cultured vascular SMCs and in murine arterial vasculature led to loss of differentiation and reduced contractility due to impaired recruitment of the DNA methylcytosine dioxygenase TET2. H3K4me2 editing altered SMC adaptative capacities during vascular remodeling due to loss of miR-145 expression. Finally, H3K4me2 editing induced a profound alteration of SMC lineage identity by redistributing H3K4me2 toward genes associated with stemness and developmental programs, thus exacerbating plasticity. Our studies identify the H3K4me2-TET2-miR145 axis as a central epigenetic memory mechanism controlling cell identity and function, whose alteration could contribute to various pathophysiological processes. [Display omitted] • Gene-selective epigenome editing reveals that H3K4me2 controls SMC lineage identity • H3K4me2 editing induces loss of contractility and exacerbates phenotypic plasticity • H3K4me2 interacts with TET2 and mediates TET-dependent gene activation • Loss of H3K4me2 impairs SMC-mediated vascular remodeling due to miR-145 deficiency Regulating the contractile states of smooth muscle cells (SMCs) is critical for vascular homeostasis. Liu et al. find that the H3K4me2 modification is required to maintain SMC lineage identity and contractile state, serving as a genomic footprint for TET2-mediated DNA demethylation. H3K4me2 alteration in SMCs may contribute to cardiovascular disease. [ABSTRACT FROM AUTHOR]