Expression of the bcl-2 gene in mouse B lymphocytic cell lines is differentiation stage specific.

cDNA clones of mouse bcl-2 have been isolated and characterized by homology to the human bcl-2 gene, a putative oncogene that is found on the portion of chromosome 18 characteristically involved in the t(14;18) translocation present in nearly all human follicular B cell lymphomas. Our mouse cDNA clone detects 7.9 and 6.3-kb bcl-2 RNAs in mouse B cell lymphomas, but only in tumors consisting of pre-B and follicular center mature B cells, not in pro-B cell or plasma cell tumors. Thus, this gene appears to be a B cell differentiation marker that is expressed only in committed B cells, but is shut off in end stage plasma cells. This pattern of expression is unique among oncogenes, and we suggest that it may be responsible for the high frequency of translocations at this locus in the common malignancy of human mature B cells, follicular lymphomas.