Proceedings of the National Academy of Sciences | 2021
Fli1+ cells transcriptional analysis reveals an Lmo2–Prdm16 axis in angiogenesis
Abstract
Significance Understanding the molecular signals driving the development of vascular endothelium is important in seeking therapies for human disease. This work highlights the role of an epigenetic modifier and oncogene in the development of the vascular endothelium and angiogenesis in zebrafish. In particular, we show that the expression of the histone methyltransferase prdm16 is high in endothelial cells and that prdm16 is necessary for the endothelial differentiation and migration in vivo and in vitro in iPSC-derived endothelial cells. Moreover, prdm16 expression is mediated by Lmo2, a well-known oncogene implicated in angiogenesis and leukemogenesis. We hence unveil a role of prdm16 in endothelial development and angiogenesis and therefore propose that PRDM16 could be a target for therapeutic modulation of angiogenesis. A network of molecular factors drives the development, differentiation, and maintenance of endothelial cells. Friend leukemia integration 1 transcription factor (FLI1) is a bona fide marker of endothelial cells during early development. In zebrafish Tg(fli1:EGFP)y1, we identified two endothelial cell populations, high-fli1+ and low-fli1+, by the intensity of green fluorescent protein signal. By comparing RNA-sequencing analysis of non-fli1 expressing cells (fli1−) with these two (fli1+) cell populations, we identified several up-regulated genes, not previously recognized as important, during endothelial development. Compared with fli1− and low-fli1+ cells, high-fli1+ cells showed up-regulated expression of the zinc finger transcription factor PRDI-BF1 and RIZ homology domain containing 16 (prdm16). Prdm16 knockdown (KD) by morpholino in the zebrafish larva was associated with impaired angiogenesis and increased number of low-fli1+ cells at the expense of high-fli1+ cells. In addition, PRDM16 KD in endothelial cells derived from human-induced pluripotent stem cells impaired their differentiation and migration in vitro. Moreover, zebrafish mutants (mut) with loss of function for the oncogene LIM domain only 2 (lmo2) also showed reduced prdm16 gene expression combined with impaired angiogenesis. Prdm16 expression was reduced further in endothelial (CD31+) cells compared with CD31− cells isolated from lmo2-mutants (lmo2-mut) embryos. Chromatin immunoprecipitation–PCR demonstrated that Lmo2 binds to the promoter and directly regulates the transcription of prdm16. This work unveils a mechanism by which prdm16 expression is activated in endothelial cells by Lmo2 and highlights a possible therapeutic pathway by which to modulate endothelial cell growth and repair.