IDENTIFICATION OF A YEAST ARTIFICIAL CHROMOSOME (YAC) SPANNING THE SYNOVIAL SARCOMA-SPECIFIC T(X 18)(P11.2 Q11.2) BREAKPOINT

A somatic cell hybrid containing the synovial sarcoma-associated t(X;18)(p11.2;q11.2) derivative (der(X)) chromosome was used to characterize the translocation breakpoint region on the X chromosome. By using Southern hybridization of DNA from this der(X) hybrid in conjunction with Xp-region specific radiation reduced cell hybrids and probes, it was found that this breakpoint maps within the ornithine aminotransferase (OAT) L1 cluster. A yeast artificial chromosome (YAC) clone (OAT YAC2) which hybridizes to a human OAT cDNA probe and is known to contain part of the OATL1 luster was selected and used to confirm these results both by fluorescence in situ hybridization on synovial sarcoma patient material and by hybridization of its end-clones to the der(X) containing hybrid cells. It was found that indeed the human Xp sequences contained within this YAC are split as a consequence of the (X;18) translocation. Therefore, we conclude that OAT YAC2 spans the synovial sarcoma-specific translocation breakpoint and, as such, may serve as an ideal starting point from which the gene(s) involved in the development of this soft tissue tumor can be isolated.