A 2-MB YAC CONTIG AND PHYSICAL MAP COVERING THE CHROMOSOME 8Q12 BREAKPOINT CLUSTER REGION IN PLEOMORPHIC ADENOMAS OF THE SALIVARY-GLANDS

Pleomorphic adenomas are benign epithelial tumors originating from the major and minor salivary glands. Extensive cytogenetic studies have d emonstrated that they frequently show chromosome abnormalities involvi ng chromosome 8, with consistent breakpoints at 8q12, In previous stud ies, we have shown that these breakpoints are located in a 9-cM interv al between MOS/D8S285 and D8S260. Here, we describe directional chromo some walking studies starting from D8S260 as well as D8S285. Using the CEPH and ICRF YAC libraries, these studies resulted in the constructi on of two nonoverlapping YAC contigs of about 2 and 5 Mb, respectively . Initial fluorescence in situ hybridization (FISH) analysis suggested that the majority of 8q12 breakpoints clustered within the 2-Mb conti g, which was mapped to the centromeric part of chromosome band 8q12. T his contig has at least double coverage and consists of 34 overlapping YAC clones, The localization of the YACs was confirmed by FISH analys is. On the basis of mapping data of landmarks with an average spacing of 65 kb as well as restriction enzyme analysis, a long-range physical map was established for the chromosome region spanned by the 2-Mb con tig. The relative positions of various known genes and expressed seque nce tags within this contig were also determined. Subsequent FISH anal yses of pleomorphic adenomas using YACs as well as cosmids revealed th at all but two of the 8q12 breakpoints in the primary tumors tested ma pped within a 300-kb interval between the MOS proto-oncogene and STS E M156. The target gene affected by the chromosome aberrations mapping w ithin this interval was recently shown to be the PLAG1 gene, which enc odes a novel zinc finger protein. (C) 1997 Academic Press.