LAF4, an AF4-related gene, is fused to MLL in infant acute lymphoblastic leukemia

Infant acute lymphoblastic leukemia (ALL) with MLL gene rearrangements is characterized by a proB phenotype and a poor clinical outcome. We analyzed an infant proB ALL with t(2; 11)(p 15;p 14) and an MLL rearrangement on Southern blot analysis, Rapid amplification of cDNA ends-polymerase chain reaction (PCR) and reverse transcriptase-PCR identified the LAF4 gene mapped on chromosome region 2q11.2-q12 as a fusion partner of the MLL gene. The LAF4 gene was identified previously by its high sequence homology to the AF4 protein and encodes a protein of 1,227 amino acids. The t(4:11)(q21:q23), creating the MLL-AF4 chimeric transcripts, is the predominant I I q23 chromosome translocation in infant ALL and is associated with an extremely poor prognosis. Our findings further suggest that fusion of MLL to one of the AF4 family members (AF4/LAF4/ AF5Q31) might determine a proB-cell phenotype in infant leukemia. (C) 2002 Wiley-Liss. Inc.