title: The histone methyltransferase MLL is an upstream regulator of endothelial-cell sprout formation.
abstract: Posttranslational histone modification by acetylation or methylation regulates gene expression. Here, we investigated the role of the histone lysine methyltransferase MLL for angiogenic functions in human umbilical vein endothelial cells. Suppression of MLL expression by siRNA or incubation with the pharmacologic methyltransferase inhibitor 5'-deoxy-5'-(methylthio)adenosine significantly decreased endothelial-cell migration and capillary sprout formation, indicating that methyltransferase activity is required for proangiogenic endothelial-cell functions. Because the expression of homeodomain transcription factors (Hox) is regulated by MLL, we elucidated the role of Hox gene expression. MLL silencing was associated with reduced mRNA and protein expression of HoxA9 and HoxD3, whereas HoxB3, HoxB4, HoxB5, and HoxB9 were not altered. Overexpression of HoxA9 or HoxD3 partially compensated for impaired migration in MLL siRNA-transfected endothelial cells, suggesting that HoxA9 and HoxD3 both contribute to MLL-dependent migration. As a potential underlying mechanism, MLL siRNA down-regulated mRNA and protein levels of the HoxA9-dependent axon guidance factor EphB4. In contrast, MLL knockdown effects on capillary sprouting were not rescued by HoxA9 or HoxD3 overexpression, indicating that MLL affects additional targets required for 3-dimensional sprout formation. We conclude that MLL regulates endothelial-cell migration via HoxA9 and EphB4, whereas sprout formation requires MLL-dependent signals beyond HoxA9 and HoxD3.
authors.affiliation: Molecular Cardiology, Department of Internal Medicine III, University of Frankfurt, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Diehl
authors.forename: Lothar
authors.initials: L
authors.lastname: Rössig
authors.forename: Andreas M
authors.initials: AM
authors.lastname: Zeiher
authors.forename: Stefanie
authors.initials: S
authors.lastname: Dimmeler
authors.forename: Carmen
authors.initials: C
authors.lastname: Urbich
mesh_terms: D002465:Cell Movement; D042783:Endothelial Cells / Q000166:cytology; D004730:Endothelium, Vascular / Q000166:cytology*; D005786:Gene Expression Regulation / Q000502:physiology; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology; D006801:Humans; D051788:Myeloid-Lymphoid Leukemia Protein / Q000502:physiology*; D018919:Neovascularization, Physiologic; D011496:Protein Methyltransferases; D011499:Protein Processing, Post-Translational
chemical_list: D018398:Homeodomain Proteins; C497422:KMT2A protein, human; D051788:Myeloid-Lymphoid Leukemia Protein; D000076983:Histone Methyltransferases; D011496:Protein Methyltransferases; D011495:Histone-Lysine N-Methyltransferase