1. ¹Department of Molecular Laboratory Medicine, Kyoto Prefectural University of Medicine Graduate School of Medical Science, Kamigyo-ku, Kyoto, Japan
2. ²Department of Molecular Hematology and Oncology, Kyoto Prefectural University of Medicine Graduate School of Medical Science, Kamigyo-ku, Kyoto, Japan
3. ³Department of Pediatrics, Ibaraki Children's Hospital, Futabadai, Mito, Japan
4. ⁴Gunma Children's Medical Center, Shimohakoda, Hokkitsu, Shibukawa, Gunma, Japan

Correspondence: Dr T Taki, Department of Molecular Laboratory Medicine, Kyoto Prefectural University of Medicine Graduate School of Medical Science, 465 Kajii-cho Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan. E-mail: taki-t@umin.net

Received 4 May 2007; Revised 13 September 2007; Accepted 17 September 2007; Published online 29 October 2007.

Abstract

The AML1 gene is frequently rearranged by chromosomal translocations in acute leukemia. We identified that the LAF4 gene on 2q11.2–12 was fused to the AML1 gene on 21q22 in a pediatric patient having T-cell acute lymphoblastic leukemia (T-ALL) with t(2;21)(q11;q22) using the bubble PCR method for cDNA. The genomic break points were within intron 7 of AML1 and of LAF4, resulting in the in-frame fusion of exon 7 of AML1 and exon 8 of LAF4. The LAF4 gene is a member of the AF4/FMR2 family and was previously identified as a fusion partner of MLL in B-precursor ALL with t(2;11)(q11;q23), although AML1-LAF4 was in T-ALL. LAF4 is the first gene fused with both AML1 and MLL in acute leukemia. Almost all AML1 translocations except for TEL-AML1 are associated with myeloid leukemia; however, AML1-LAF4 was associated with T-ALL as well as AML1-FGA7 in t(4;21)(q28;q22). These findings provide new insight into the common mechanism of AML1 and MLL fusion proteins in the pathogenesis of ALL. Furthermore, we successfully applied bubble PCR to clone the novel AML1-LAF4 fusion transcript. Bubble PCR is a powerful tool for detecting unknown fusion transcripts as well as genomic fusion points.