PRDM6 is enriched in vascular precursors during development and inhibits endothelial cell proliferation, survival, and differentiation

Abstract

The mechanisms that regulate the differentiation program of multipotential stem cells remain poorly understood. In order to define the cues that delineate endothelial commitment from precursors, we screened for candidate regulatory genes in differentiating mouse embryoid bodies. We found that the PR/SET domain protein, PRDM6, is enriched in flk1(+) hematovascular precursor cells using a microarray-based approach. As determined by 5′ RACE, full length PRDM6 protein contains a PR domain and four Krüpple-like zinc fingers. In situ hybridization in mouse embryos demonstrates staining of the primitive streak, allantois, heart, outflow tract, para-aortic splanchnopleura (P-Sp)/ aorto-gonadal-mesonephric (AGM) region and yolk sac, all sites known to be enriched in vascular precursor cells. PRDM6 is also detected in embryonic and adult-derived endothelial cell lines. PRDM6 is co-localized with histone H4 and methylates H4-K20 (but not H3) in vitro and in vivo, which is consistent with the known participation of PR domains in histone methyltransferase activity. Overexpression of PRDM6 in mouse embryonic endothelial cells induces apoptosis by activating caspase-3 and inducing G1 arrest. PRDM6 inhibits cell proliferation as determined by BrdU incorporation in endothelial cells, but not in rat aortic smooth muscle cells. Overexpression of PRDM6 also results in reduced tube formation in cultured endothelial cells grown in Matrigel. Taken together, our data indicate that PRDM6 is expressed by vascular precursors, has differential effects in endothelial cells and smooth muscle cells, and may play a role in vascular precursor differentiation and survival by modulating local chromatin-remodeling activity within hematovascular subpopulations during development.

Expression patterns of PRDM10 during mouse embryonic development

“…It is known that most of the PR/SET gene family modulates gene expression, specifically the spatial and temporal regulation of tissue differentiation during mouse embryonic development (5,15,19,20). Functionally, PR/SET gene family members directly or indirectly interact with histone methylation proteins that possess HMTase activity as well as components of the transcription machinery (1,8,11).…”

The Prdm family: expanding roles in stem cells and development

“…Furthermore, although most SET family members are enzymatically active, HMT activity has been found only in the PR domains of Prdm2, Prdm8 and Prdm9 (also called Meisetz; meiosis-induced factor containing PR/SET domain and zinc-finger motif) (Derunes et al, 2005;Eom et al, 2009;Hayashi et al, 2005). Activity has also been reported for Prdm6 (also called Prism -Prdm in smooth muscle); however, Prdm6 constructs that lack a PR domain still retain histone H4 methyltransferase activity and the nature of this activity requires further clarification (Wu et al, 2008).…”

PRDM proteins: Important players in differentiation and disease

“…This capacity is shared by PRDM1 [9,13], PRDM5 [10], and PRDM6 [11], although data suggest that PRDM proteins appear to reside in different protein complexes in a cell type and promoter-dependent manner. Indeed, PRDM1 was shown to associate with the PRMT5 arginine methyltransferase in germ cells [14] and with the LSD1 demethylase in plasma cells [15], while PRDM6 has been associated with H4K20 methylation in endothelial cells [16], as well as histone acetylation in smooth muscle cells via binding to the p300 histone acetyltransferase (HAT) [11].…”

“…A PRDM6 isoform containing an additional 170 amino acids was later described to promote early vascular differentiation by inhibiting endothelial differentiation [16]. PRDM6 appears to regulate vascular differentiation of rat primary smooth muscle by promoting cell proliferation and suppressing genes associated with a differentiated phenotype [11].…”

“…PRDM6 appears to regulate vascular differentiation of rat primary smooth muscle by promoting cell proliferation and suppressing genes associated with a differentiated phenotype [11]. However, the long isoform of PRDM6 does not promote proliferation of a rat aortic smooth muscle cell line, but instead PRDM6 overexpression induces cell cycle arrest and apoptosis in endothelial cells [16]. Different cells and/or different isoforms of PRDM6 used in these different studies may account for this discrepancy.…”