Identification of an ETV6-ABL2 fusion transcript in combination with an ETV6 point mutation in a T-cell acute lymphoblastic leukaemia cell line

ETV6, a member of the Ets family of transcription factors, is frequently rearranged to various translocation partners in human leukaemias. We previously described a CD3(+)/TCRalpha/beta(+) mature T-cell acute lymphoblastic leukaemia (T-ALL) cell line, MT-ALL, carrying a t(1;10;12)(q25; p13; p13) with cytokine-inducible lineage switch into the myeloid lineage. Using reverse transcription polymerase chain reaction with primers complementary to ETV6 and ABL2, two ETV6-ABL2 fusion transcripts were identified in MT-ALL which resulted from alternative splicing of an ABL2 exon. The fusion transcripts code for putative ETV6-ABL2 fusion proteins containing the pointed domain of ETV6 and almost the complete ABL2 protein, including the SH2, SH3 domains and the protein tyrosine kinase domain (PTK). Identical ETV6-ABL2 fusion transcripts have been reported in an acute myeloid leukaemia (AML) M3 cell line, carrying both a t(15; 17)(q22; q21) and a t(1; 12)(q25; p13) with unusual inducible differentiation to eosinophils, and in a patient with AML-M4eo. Interestingly, the non-rearranged allele of ETV6 in the MT-ALL cell line carries an arginine to histidine (R399H) mutation which affects a conserved amino acid in the ets DNA binding domain.