Expression and functional analysis of a hemopoietic progenitor antigen, NJ-1 (114/A10), in the megakaryocytic lineage

To analyze the functions of molecules expressed in hemopoietic progenitor cells, we obtained several monoclonal antibodies by immunizing Wistar rats with antigens from a murine immature leukemic cell line, DA-1, Here, we characterize one antibody designated NJ-l, which recognizes a 145-kd molecule, and identify the cDNA encoding the NJ-l antigen by retrovirus-mediated expression cloning. Sequence analysis of the cDNA reveals that it is identical to a previously reported cDNA encoding a surface molecule of 573 amino acids recognized by monoclonal antibody 114/A10. Our studies show that expression of NJ-l antigen is upregulated in a murine megakaryoblastic cell line, L8057, when it differentiates into a megakaryocytic lineage in response to 12-O-tetradecanoyl phorbol-13-acetate. Overexpression of NJ-l antigen in L8057 cells inhibits cell adhesion to fibronectin, suggesting that it may act as a negative regulator of cell adhesion in the megakaryocytic lineage. (C) 1998 Academic Press.