CLOSING IN ON THE RIEGER SYNDROME GENE ON 4Q25 - MAPPING TRANSLOCATION BREAKPOINTS WITHIN A 50-KB REGION

Rieger syndrome (RGS) is an autosomal dominant disorder of morphogenes is affecting mainly the formation of the anterior eye chamber and of t he teeth. RGS has been localized to human chromosome 4q25 by linkage t o epidermal growth factor (EGF). We have constructed a detailed physic al map and a YAC contig of the genomic region encompassing the EGF loc us. Using FISH, several YACs could be shown to cross the breakpoint in two independent RGS patients with balanced 4q translocations. Alu- an d LINE-fragmentation of a 2.4-Mb YAC generated a panel of shorter YACs ranging in size from 2.4 Mb to 75 kb. Several fragmentation YACs were subcloned in cosmids, which were mapped to specific subregions of the original YAC by hybridization to the fragmentation panel to further r efine the localization of the translocation breakpoints, allowing mapp ing of the breakpoints to within the most-telomeric 200 kb of the orig inal 2.4-Mb YAC. FiberFISH of cosmids located in this 200-kb region ma pped the two translocation breakpoints within a 50-kb region similar t o 100-150 kb centromeric to D4S193, significantly narrowing down the c andidate region for RGS. The mapping data and resources reported here should facilitate the identification of a gene implicated in Rieger sy ndrome.