Coexistence of alternative MLL-SEPT9 fusion transcripts in an acute myeloid leukemia with t(11;17)(q23;q25).

We present the characterization at the RNA level of an acute myeloid leukemia with a t(11;17)(q23;q25) and a MLL rearrangement demonstrated by FISH. Molecular analysis led to the identification of two coexistent in-frame MLL-SEPT9 fusion transcripts (variants 1 and 2), presumably resulting from alternative splicing. Real-time quantitative RT-PCR analysis showed that the relative expression of the MLL-SEPT9 fusion variant 2 was 1.88 fold higher than the relative expression of MLL-SEPT9 fusion variant 1. This is the first description of a MLL-SEPT9 fusion resulting in coexistence of two alternative splicing variants, each of which previously found isolated in myeloid leukemias.
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