hide
Free keywords:
Cell Movement/drug effects
Cells, Cultured/cytology/drug effects/metabolism
Endothelial Cells/cytology/drug effects/metabolism
Endothelium, Vascular/cytology/*metabolism
*Gene Expression Regulation
Homeodomain Proteins/chemistry/genetics/*physiology
Humans
Morphogenesis
Mutagenesis, Site-Directed
Neovascularization, Physiologic/genetics/*physiology
Oligonucleotides, Antisense/pharmacology
Promoter Regions, Genetic/genetics
RNA Interference
RNA, Small Interfering/pharmacology
Receptor, EphB4/biosynthesis/genetics/*physiology
Recombinant Fusion Proteins/physiology
Sequence Deletion
*Transcription, Genetic
Abstract:
Homeobox genes (Hox) encode for transcription factors, which regulate cell proliferation and migration and play an important role in the development of the cardiovascular system during embryogenesis. In this study, we investigated the role of HoxA9 for endothelial cell migration and angiogenesis in vitro and identified a novel target gene, the EphB4 receptor. Inhibition of HoxA9 expression decreased endothelial cell tube formation and inhibited endothelial cell migration, suggesting that HoxA9 regulates angiogenesis. Because Eph receptor tyrosine kinases importantly contribute to angiogenesis, we examined whether HoxA9 may transcriptionally regulate the expression of EphB4. Downregulation of HoxA9 reduced the expression of EphB4. Chromatin-immunoprecipitation revealed that HoxA9 interacted with the EphB4 promoter, whereas a deletion construct of HoxA9 without DNA-binding motif (Delta(aa) 206-272) did not bind. Consistently, HoxA9 wild-type overexpression activated the EphB4 promoter as determined by reporter gene expression. HoxA9 binds to the EphB4 promoter and stimulates its expression resulting in an increase of endothelial cell migration and tube forming activity. Thus, modulation of EphB4 expression may contribute to the proangiogenic effect of HoxA9 in endothelial cells.
