PARTIAL DUPLICATION OF HRX IN ACUTE-LEUKEMIA WITH TRISOMY-11

The HRX gene has recently been shown to be involved in most of the chr omosomal abnormalities of band 11q23 frequently present in human hemat ological malignancies. Rearrangements are strikingly diverse, but most affect a restricted area of the HRX gene and lead to gene fusion betw een HRX and a gene located on the partner chromosome. Another kind of HRX alteration seen in human acute leukemia is a partial duplication o f the NH2 part of the HRX locus. We have characterized two cases of pa rtial HRX duplication in acute leukemias bearing trisomy 11 as the sol e chromosomal abnormality. In one patient analyzed at the genomic leve l, an Alu repeat was involved within exon 6 but not within intron 1. S plicing of exon 6 to exon 2 was observed in this patient while splicin g of exon 8 to exon 2 was observed in the other. Our data indicated th at HRX duplication is highly similar to the translocation affecting th e HRX locus both in the restricted diversity of the fusion points and the involvement of Alu repeats within the breakpoint cluster region (e xon 5 to 10).