Lmo2 (LIM-Domain-Only 2) Modulates Sphk1 (Sphingosine Kinase) and Promotes Endothelial Cell Migration.

OBJECTIVE

(LIM-domain-only)2 transcription factor is involved in hematopoiesis and vascular remodeling. (sphingosine kinase)1 phosphorylates sphingosine to S1P (sphingosine-1-phosphate). We hypothesized that regulates to promote endothelial cell (EC) migration and vascular development. APPROACH AND RESULTS: and knockdown (KD) were performed in ) zebrafish and in human umbilical vein EC. Rescue of phenotypes or overexpression of these factors were achieved using mRNA encoding or . EC proliferation in vivo was assessed by BrdU (bromodeoxyuridine) immunostaining and fluorescence-activated cell sorter analysis of dissociated ) embryos. Cell migration was assessed by scratch assay in human umbilical vein EC and mouse aortic rings. interactions with promoter were assessed by ChIP-PCR (chromatin immunoprecipitation-polymerase chain reaction). or KD reduced number and length of intersegmental vessels. There was no reduction in the numbers of GFP (green fluorescent protein) ECs after KD. However, reduced numbers of BrdUGFP nuclei were observed along the dysmorphic intersegmental vessels, accumulating instead at the sprouting origin of the intersegmental vessels. This anomaly was likely because of impaired EC migration, which was confirmed in migration assays using KD human umbilical vein ECs and mouse aortic rings. Both in vivo and in vitro, KD reduced gene expression, associated with less binding to the promoter as assessed by ChIP-PCR. mRNA rescued the KD phenotype.

CONCLUSIONS

Our data showed that is necessary for gene expression in ECs. KD reduced - gene interaction, impaired intersegmental vessels formation, and reduced cell migration. We identified for the first time as downstream effector of .