Article

Analysis of genomic breakpoints in p190 and p210 BCR–ABL indicate distinct mechanisms of formation

Wessex Regional Genetics Laboratory, Salisbury and Human Genetics Division, University of Southampton School of Medicine, Southampton, UK.
Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K (Impact Factor: 9.38). 10/2010; 24(10):1742-50. DOI: 10.1038/leu.2010.174
Source: PubMed

ABSTRACT We sought to understand the genesis of the t(9;22) by characterizing genomic breakpoints in chronic myeloid leukemia (CML) and BCR-ABL-positive acute lymphoblastic leukemia (ALL). BCR-ABL breakpoints were identified in p190 ALL (n=25), p210 ALL (n=25) and p210 CML (n=32); reciprocal breakpoints were identified in 54 cases. No evidence for significant clustering and no association with sequence motifs was found except for a breakpoint deficit in repeat regions within BCR for p210 cases. Comparison of reciprocal breakpoints, however, showed differences in the patterns of deletion/insertions between p190 and p210. To explore the possibility that recombinase-activating gene (RAG) activity might be involved in ALL, we performed extra-chromosomal recombination assays for cases with breakpoints close to potential cryptic recombination signal sequence (cRSS) sites. Of 13 ALL cases tested, 1/10 with p190 and 1/3 with p210 precisely recapitulated the forward BCR-ABL breakpoint and 1/10 with p190 precisely recapitulated the reciprocal breakpoint. In contrast, neither of the p210 CMLs tested showed functional cRSSs. Thus, although the t(9;22) does not arise from aberrant variable (V), joining (J) and diversity (D) (V(D)J) recombination, our data suggest that in a subset of ALL cases RAG might create one of the initiating double-strand breaks.

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