Easy detection of all T cell receptor gamma (TCRG) gene rearrangements by Southern blot analysis: recommendations for optimal results

Southern blot analysis of T cell receptor (TCR) gene rearrangements has pro ven to be a helpful tool to establish clonality in T cell leukemias and lym phomas. To improve the detection of clonal TCR gamma (TCRG) gene rearrangem ents by Southern blot analysis, we designed four new Jy probes and determin ed the most optimal restriction enzymes to be used with these probes. Based on detailed analysis of the sequences as well as on hybridization experime nts with the TCRGJ21 probe, the J gamma 1.2 and J gamma 2.1 downstream area s were found to be highly homologous, suggesting that during evolution the duplication of the Jy region was followed by deletion of the tentative J ga mma 2.2 gene segment. Southern blot analysis of 51 T cell acute lymphoblast ic leukemias (T-ALL) revealed that all TCRG gene rearrangements can be dete cted by use of the TCRGJ13 probe in EcoRI digests and the TCRGJ21 probe in Pstl digests. Additional probes and digests allow a more precise identifica tion of the exact type of TCRG gene rearrangements in the majority of cases . Almost 90% of the TCRG gene rearrangements in T-ALL involved the J gamma 2 region (16% J gamma 2.1 and 72% J gamma 2.3), whereas J gamma 1 region re arrangements were particularly found in TCR gamma delta(+); T-ALL. This inf ormation has implications for design of primer sets for PCR analysis at dia gnosis and for PCR target choice in detection of minimal residual disease d uring follow-up of T-ALL patients.