CHARACTERIZATION OF THE RARE TRANSLOCATION T(3;10)(Q26;Q21) IN AN ACUTE MYELOID LEUKEMIA PATIENT

ABSSUB-3966

Background: Recently, we introduced a flexible strategy for mapping cytogenetically identified unique abnormalities down to the single nucleotide level. This strategy has enabled us to design clone-specific assays for sensitive minimal residual disease (MRD) monitoring in acute leukemia patients (Jancuskova et al. Leuk Res. 2013) as well as to elucidate regions/genes involved in congenital chromosomal aberrations (unpublished data).

Here we characterize the rare chromosomal translocation t(3;10)(q26;q21), involving the MECOM gene (MDS and EVI1 complex locus located in band 3q26), identified in an acute myeloid leukemia (AML) patient.

Aims: Our aim was to use our strategy to identify the fusion partner on chromosome 10q21 and to characterize the precise nucleotide sequence of the chromosomal breakpoint.

Methods: The chromosomal translocation was revealed by standard cytogenetic techniques (G-banding, mFISH), and involvement of the MECOM gene was confirmed by FISH with the use of a commercially available probe set. The derivative chromosome 10 was isolated using fine-needle microdissection followed by whole genome amplification (WGA). Ten dissected fragments were sequenced on the GS-Junior next-generation sequencing platform. The reads obtained were aligned to reference sequences of chromosomes 3 and 10 using in-house developed software. The last mapped reads from both chromosomes were used as docking sites for primers for long-range PCR to amplify the putative breakpoint. The long-range PCR products were directly sequenced using Sanger sequencing to reveal the precise nucleotide sequence of the breakpoint.

Results: Using a combination of cytogenetic and molecular approaches, we mapped the t(3;10)(q26;q21) to the single nucleotide level, revealing a fusion of the MECOM gene (3q26.2) and C10orf107 (10q21.2).

Keywords: Acute myeloid leukemia, Minimal residual disease (MRD), Molecular markers

Summary/Conclusion: In AML patients, the MECOM gene can be rearranged with a variety of other partner chromosomes and partner genes. According to the Mitelman database, only one case with a t(3;10)(q26;q21) translocation has been reported, but neither the fusion partner of the MECOM gene nor DNA sequence were identified. The approach described here opens up new possibilities in characterizing acquired as well as congenital chromosomal aberrations. In addition, DNA sequences of chromosomal breakpoints may be a useful tool for unique molecular MRD target identification in acute leukemia patients.

Keywords: Acute myeloid leukemia, Minimal residual disease (MRD), Molecular markers

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