Expression of the TAL1 proto-oncogene in cultured endothelial cells and blood vessels of the spleen.

The TAL1 proto-oncogene encodes a basic helix-loop-helix (bHLH) protein that has been implicated in the pathogenesis of T-cell acute lymphoblastic leukemia. Normal expression of TAL1 is observed in erythrocytic, megakaryocytic and mastocytic cells of the hematopoietic lineage. We now report that both RNA transcripts and polypeptide products of TAL1 are present in human umbilical vein endothelial cells cultured in vitro. Moreover, in situ hybridization revealed a restricted pattern of TAL1 expression in endothelial cells in vivo, including vessels within the white pulp and follicles of the spleen. In view of its presumptive role as a transcriptional factor, the TAL1 gene product may serve during normal development as a regulator of endothelial cell growth or differentiation.