Molecular genetic characterization of the genomic ACTB-GLI fusion in pericytoma with t(7;12).

"Pericytoma with t(7;12)" is a newly defined soft tissue tumor characterized by fusion of the ACTB and GLI genes through the translocation t(7;12)(p22;q13). Recently, we reported the structure of the ACTB-GLI and GLI-ACTB fusion transcripts in five cases, and herein the corresponding genomic breakpoints were investigated. Overall, the findings at the DNA level corresponded well with the structure of the expressed transcripts. In three cases, the fusions were due to junction of intronic sequences, in two cases breakpoints were found in exonic sequences. In four cases the fusions corresponded to the juxtapositioning of unaltered DNA sequences, and in one case, a micro-inversion was found at the junction. All five fusions were molecularly unbalanced, including the two cases with reciprocal GLI-ACTB chimeras. Whereas large repeats or recombinase recognition sequences were not detected, sequences of shared oligonucleotides, possibly important for recombination, were found in the proximity of the respective breakpoints.