Gene targeting of the KI-KII sequence elements in a model pre-B cell line: Effects on germline transcription and rearrangement of the κ locus

To study the role of individual sequence elements in the coordinate regulation of rearrangement and germline transcription of the κ locus, we have developed a gene targeting system with a mouse model pre-B cell line, 38B9. This line can be induced to initiate κ germline transcription and V-J rearrangement. Importantly, the effects of gene disruption in the cell line can be analyzed independent of selective pressures that may mask effects in the developing immune system of the mouse. We focused our study on targeting mutation of the endogenous KI-KII sequence elements to allow a direct comparison with the same gene disruption reported in mouse studies. Mutations were targeted to one allele, and effects on induced transcription and rearrangement were compared to the remaining wild type allele. Our results show that KI-KII mutation has little effect on germline transcription, and reduced the frequency of rearrangement two fold compared to the wild type allele. This report demonstrates that the use of model pre-B cell lines for targeted gene disruption is an attractive alternative to targeting the germline of the mouse.