Amplification and rearrangement of melF/mouse CD43 (leukosialin) gene encoding a highly glycosylated membrane protein gp120 in Friend erythroleukemia cells.

Using a differential hybridization method, we isolated a cDNA (melF) overexpressed in a murine Friend erythroleukemia cell line, F5-5. Southern blotting and sequence analysis revealed that the melF cDNA encodes a membrane protein of 395 amino acids that is the couterpart to human CD43 (leukosialin) surface antigen of lymphocytes in mice. The melF/mouse CD43 (mCD43) gene was found to be amplified eight- to 10-fold not only in F5-5 cells, but also in their sib cell lines, including the earliest clone established. This indicates that the amplification of melF/mCD43 gene occurred at an early stage of malignant transformation of the F5-5 family. Furthermore, the same gene was rearranged in another Friend erythroleukemia cell line TSA8. In both cell lines, F5-5 and TSA8, the levels of melF/mCD43 mRNA were 30- to 50-fold higher than that in uninfected spleen cells. Among normal tissues examined, the expression of melF/mCD43 gene was restricted to hematopoietic tissues. These results suggest that melF/mCD43 gene has an important role in progression of leukemic cells in the erythroid lineage and also has a physiological function in normal hematopoiesis.