INDUCED REARRANGEMENT OF KAPPA-GENES IN THE BLIN-1 HUMAN PRE-B CELL-LINE CORRELATES WITH GERMLINE J-C-KAPPA AND V-KAPPA TRANSCRIPTION

The human pre-B acute lymphoblastic leukemia cell line, BLIN-1, has been previously shown to undergo kappa-light chain rearrangement in vitro, making it a valuable resource for analyzing pre-B to B cell differentiation. We have examined the recombination potential of BLIN-1 by characterizing several independently derived kappa-expressing subclones for DNA rearrangement and V-kappa gene usage. Analysis of five kappa-expressing subclones (all having the same heavy chain rearrangement) demonstrated independent kappa-light chain rearrangement events by DNA hybridization analysis. Northern blot analysis using probes recognizing the four different V-kappa families revealed that two subclones used the most proximal V-kappa (V-kappa-IV), one subclone used a V-kappa-I, and one subclone used a V-kappa-II. By polymerase chain reaction analyses, we detected transcripts from rearranged V-J-C-kappa genes as well as transcripts from germline J-C-kappa and V-kappa in BLIN-1 cells induced to rearrange the kappa-locus. Kappa-germline transcripts were also detected in normal developing B cell populations in fetal liver and bone marrow. Our collective results indicate that: (a) BLIN-1 can be induced to rearrange the kappa-locus, and this correlates with the expression of germline kappa-locus transcripts that may play a role in activating or targeting gene rearrangement; and (b) active rearrangement and usage of V genes representing different kappa-families suggest that, like in the mouse, repertoire diversification in humans occurs in the presence of a fixed heavy chain rearrangement.