Cloning and sequencing of a t(14;19) breakpoint that involves the Cμ switch region

The t(14;19) is a recurring translocation found in a small number of cases of chronic B‐cell leukemia (CLL). We have cloned and sequenced the breakpoint in a patient with a t(14;19) and shown that the breakpoint on chromosome 14 occurred in the Cμ switch region, and that the breakpoint on chromosome 19 occurred in the 5′ untranslated region of the BCL3 gene. This is in contrast to all the other reported cases with a t(14;19) in which the breakpoints on chromosome 14 occurred in the Cαl or Cα2 switch region, and the breakpoints on chromosome 19 occurred upstream of the BCL3 gene. Our results further emphasize the importance of the switch region in the t(14;19) translocation. © 1993 Wiley‐Liss, Inc.