Derivative (1) t(1;1) (p36; q21) Produces the Fusion Protein with Phosphatase 10 and MEL1 (MDS1/EVI1-Like Gene 1) in a AML (M5a) Case.

Objective: A 25 years-old Japanese male was diagnosed as AML (M5a) with 46, XY, der (1) t(1; 1) (p36; q21). To determine the leukemogenesis in this case, we analyzed the fusion product of this chromosomal translocation.

Method: After obtaining informed consent, RNA was extracted from his bone marrow cells (blastic cells were occupied in almost 100%) with GTC method, and poly-A rich RNA was separated with oligo-dT latex particles. 1^st strand cDNA was synthesized with oligo-dT primer. Oligo-dA stretch was added with TdT to make 5′ RACE. 1^st PCR was performed with the synthetic antisense-1 primers from several candidates including p73, and MEL1, and with QT primer (5′-TGAGCCAGAGTGACGAGGACTCGAGCTCAAGCT¹⁷-3′) as a sense primer. 2^nd PCR was performed with internal antisense-2 primers from several candidates, and Q0 primer (5′-CCAGTGAGCAGAGTGACG-3′) as the sense primer. The reaction of DNA sequencing was performed with BigDye Terminator Cycle Sequencing kit (Applied Biosystems), and analyzed with ABI Prism 3700 DNA analyzer.

Result and Discussion: The fusion cDNA product was obtained, which was consisted of MEL1 and Phosphatase 10. The breakpoint of MEL1 was exon 4, and PR domain of MEL1 was disrupted. This domain is reported to be the key function of MEL1, and when MEL1 without PR domain is expressed, myeloid differentiation is blocked. In this case the fusion of Phosphatase 10 and MEL1 is seemed to be the main cause of leukemogenesis.