GENE-EXPRESSION OF LIPID-BINDING PROTEIN TRANSFERRED THE ABILITY OF SPECIFIC ATTACHMENT OF HEMATOPOIETIC-CELLS TO NON-SUPPORTIVE STROMAL CELL-LINE, MS-K

In order to identify the cDNAs responsible for hemopoietic supportive activity, expression of mRNAs in hemopoietic supportive bone marrow st romal cells (MS-5) and non-supportive stromal cells (MS-K) were compar ed by the cDNA subtraction method. A subtracted MS-5-cDNA library, whi ch contains cDNA clones corresponding to mRNAs present in MS-5 cells b ut not in MS-K cells, was constructed. Screening of subtracted MS-5-cD NA library resulted in the isolation of some clones. Two of them, lipi d binding protein (LBP) and haptoglobin (Hp), were expressed specifica lly in MS-5 cells but not in MS-K cells. The genes of LBP and up were subcloned into mammalian expression vector and transfected into hemopo ietic non-supportive stromal cells line, MS-K. Then LBP-expressing sta ble transformants (MS-K-LBP) and Hp-expressing transformants (MS-K-Hp) were cloned. A rosette formation assay was carried out to investigate whether or not the LBP and up cause MS-K cells to adhere to hemopoiet ic cells, MS-K-LBP formed rosettes with hemopoietic cells as MS-5 cell s, although the MS-K-Hp and normal MS-K cells did not form rosettes. T hese data indicate that LBP expressed in hemopoietic supportive stroma l cells is partly responsible for the adhesion of hemopoietic stem cel ls to stromal cells.