THE DCC GENE - STRUCTURAL-ANALYSIS AND MUTATIONS IN COLORECTAL CARCINOMAS

DCC is a candidate tumor-suppressor gene encoding a protein with seque nce similarity to cell adhesion molecules such as N-CAM. A set of over lapping YAC clones that contains the entire DCC coding region was isol ated. Studies of this YAC contig showed that the DCC gene spans approx imately 1.4 Mb. For elucidation of exon-intron structure, lambda phage clones containing all known coding sequences were isolated from a gen omic library. These clones were used to demonstrate the existence of 2 9 DCC exons, and the sequences of the exon-intron boundaries were dete rmined for each. Twenty-three polymorphic markers from chromosome 18 w ere then studied in a panel of primary colorectal tumors that had lost some, but not all, of chromosome 18. In most of these tumors, the reg ion that was lost included DCC. Finally, Southern blot and PCR-based a pproaches were used to search for subtle mutations in several DCC exon s. One tumor that had a point mutation in exon 28 was found, resulting in a proline to histidine substitution. A second tumor with a point m utation in intron 13 was also found. The regional map and genomic stru cture of DCC should provide the means to more extensively study DCC ge ne alterations and protein function in normal and neoplastic cells. (C ) 1994 Academic Press, Inc.