CASZ1 Promotes Vascular Assembly and Morphogenesis through the Direct Regulation of an EGFL7/RhoA-Mediated Pathway

Abstract

Summary The formation of the vascular system is essential for embryonic development and homeostasis. However, transcriptional control of this process is not fully understood. Here we report an evolutionarily conserved role for the transcription factor CASZ1 in blood vessel assembly and morphogenesis. In the absence of CASZ1, Xenopus embryos fail to develop a branched and lumenized vascular system, and CASZ1-depleted human endothelial cells display dramatic alterations in adhesion, morphology, and sprouting. Mechanistically, we show CASZ1 directly regulates Epidermal Growth Factor-Like Domain 7 (Egfl7). We further demonstrate that defects of CASZ1 or EGFL7-depleted cells are in part due to diminished RhoA expression and impaired focal adhesion localization. Moreover, these abnormal endothelial cell behaviors in CASZ1-depleted cells can be rescued by restoration of Egfl7. Collectively, these studies show CASZ1 is required to directly regulate a unique EGFL7/RhoA-mediated pathway to promote vertebrate vascular development.

Casz1 is required for cardiomyocyte G1-to-S phase progression during mammalian cardiac development

“…1I-L). Given that it is not technically possible to investigate nuclear domains in cardiac tissue in vivo, we examined the compartmentalization of CASZ1 in human primary endothelial cells (HUVECS), a cell type previously shown to express CASZ1 (Charpentier et al, 2013b).…”

“…Cell culture HUVECS (Lonza) were maintained and immunostained as previously described (Charpentier et al, 2013b).…”

The CASZ1/Egfl7transcriptional pathway is required for RhoA expression in vascular endothelial cells

“…[14][15][16] We have recently further implicated RhoA-mediated signaling in vascular development by showing that RhoA lies downstream of a transcriptional cascade involving the transcription factor CASTOR (CASZ1) and its direct target Epidermal Growth Factor-like Domain 7 (Egfl7). 17,18 CASZ1 is an evolutionarily conserved transcription factor originally characterized in Drosophila to maintain neural stem cell identity. 19,20 In addition to expression domains in the brain, Casz1 transcripts have been identified in cardiovascular tissues across vertebrate species, and work from our lab demonstrated that CASZ1 is required for Xenopus cardiogenesis by regulating cardiomyocyte differentiation.…”

“…19,20 In addition to expression domains in the brain, Casz1 transcripts have been identified in cardiovascular tissues across vertebrate species, and work from our lab demonstrated that CASZ1 is required for Xenopus cardiogenesis by regulating cardiomyocyte differentiation. 17,[21][22][23] Furthermore, genome-wide association studies have revealed a genetic link between the human Casz1 locus and high blood pressure implicating CASZ1 in cardiovascular disease as well as development. 24 Through the use of Xenopus and human endothelial cell models, we have recently demonstrated that CASZ1 is also required for blood vessel development.…”

“…24 Through the use of Xenopus and human endothelial cell models, we have recently demonstrated that CASZ1 is also required for blood vessel development. 17 In the absence of CASZ1, Xenopus embryos failed to generate a well-branched vascular network and lumen formation was impaired. At the cellular level, CASZ1-depletion by short hairpin RNA in human umbilical vein endothelial cells (HUVECs) resulted in the inability of cells to maintain adhesion to the underlying substrate and failure of cells to undergo the G1/S cell cycle transition; likely due to defective control of cell contractility.…”