Mel-18, a mammalian Polycomb gene, regulates angiogenic gene expression of endothelial cells

Mel-18 is a mammalian homolog of Polycomb group (PcG) genes. Microarray analysis revealed that Mel-18 expression was induced during endothelial progenitor cell (EPC) differentiation and correlates with the expression of EC-specific protein markers. Overexpression of Mel-18 promoted EPC differentiation and angiogenic activity of ECs. Accordingly, silencing Mel-18 inhibited EC migration and tube formation in vitro. Gene expression profiling showed that Mel-18 regulates angiogenic genes including kinase insert domain receptor (KDR), claudin 5, and angiopoietin-like 2. Our findings demonstrate, for the first time, that Mel-18 plays a significant role in the angiogenic function of ECs by regulating endothelial gene expression.

Research highlights
► The expression of Mel-18, a mammalian polycomb homologue, was induced during the differentiation of endothelial progenitor cell (EPC) into endothelial cells (EC) in vitro.
► Mel-18 accelerates EPC differentiation into EC and promotes angiogenic activity of ECs in vitro.
► The expression level of several angiogenesis related genes including VEGF receptor2 (KDR) was reduced in Mel-18 knockdown ECs.