HMGIY is the target of 6p21.3 rearrangements in various benign mesenchymal tumors.

Specific chromosomal abnormalities of chromosomal region 6p21.3 have been described in subsets of many benign mesenchymal tumors. In the presented study, we investigated a series of 36 such cases by FISH, and Southern blot analyses for HMGIY rearrangements. FISH results revealed that the chromosomal breakpoints of 11 pulmonary chondroid hamartomas (PCHs), 12 endometrial polyps (EPs), one lipoma, and two uterine leiomyomas (ULs) were located within a 80 kb region surrounding the HMGIY gene. In 11 PCHs and one UL the breakpoints were located 3' of HMGIY, and one PCH showed a breakpoint 5' of HMGIY. Southern blot analyses with intra- and extragenic probes were performed of primary tumor material or cell lines from one UL, three PCHs, and five EPs. In none of these cases was an intragenic rearrangement found. Finally, we were able to detect expression of truncated HMGIY transcripts by 3'-RACE PCR. Our data clearly show the role of a further member of the HMGI family in the development of benign mesenchymal tumors. Although most of the breakpoints of the chromosomal translocations involving HMGIY are located outside the gene, aberrant transcripts resembling the structure of those observed in the case of HMGIC have been found. Our molecular investigations thus led to the identification of the molecular mechanism by which rearrangements of either of two closely related genes lead to the development of frequent benign mesenchymal tumors in humans.