The overall goal is to isolate genes responsible for craniosynostosis on chromosome 7p, which is a """"""""Center for craniosynostotic genes."""""""" The common craniosynostotic syndrome, Saethre-Chotzen, was mapped to chromosome 7p2, and the less common Greig cephalopolysyndactyly syndrome locus at 7p13 was identified as the mutated GLI3 gene. Craniosynostosis is also associated with 40% of deletions of chromosome 7p. The 1st specific aim is to isolate the Saethre-Chotzen syndrome gene and determine phenotype and genotype correlations. We have identified a balanced translocation at chromosome 7p22 [t(2;7)(p23;p22)] in a mother and son with Saethre-Chotzen syndrome. We have confirmed linkage of this disorder with DNA markers spanning the chromosome 7p arm. The tightest linkage was to locus D7S664 (S=6.230=0.00). Haplotype, linkage analysis, and physical mapping data suggest that the disease gene maps between loci D7S664 and D7S507 which flank the translocation breakpoint, suggesting that the Saethre-Chotzen syndrome gene is disrupted by the translocation. The experimental design for this specific aim is to 1) ascertain additional Saethre-Chotzen syndrome families and sporadic cases, and analyze their chromosomes for abnormalities which may further refine the gene location, 2) refine the location on the genetic map by linkage analysis with chromosome 7p2 DNA markers, 3) refine the location on the physical map by constructing yeast artificial chromosome (YAC) and cosmid contigs corresponding to the genetic map location, 4) physically map and clone the translocation breakpoint, using hybrid cell lines containing the translocation chromosomes, 5) sequence genomic DNA clones, which bridge the translocation breakpoint and isolate candidate cDNAs, 6) identify the disease gene by detecting mutations in affected individuals, and 7) perform phenotype and genotype correlations. The 2nd specific aim is to isolate craniosynostotic genes involved in the chromosome del(7p) syndrome. The experimental design for this specific aim is to 1) collect additional craniosynostotic patients with del(7p) and analyze their chromosomes, 2) determine if there are regions of minimal overlap which may define an associated contiguous gene syndrome, and 3) if there are 'critical' regions, create a corresponding YAC or cosmid contig. The contig will be screened by direct selection and exon trapping for candidate cDNAs. These candidate genes will be screened for appropriate tissue expression and mutations in known craniosynostotic syndromes (Jackson-Weiss, Crouzon, etc.). The mechanism for phenotypic expression of these craniosynostotic regions or genes will be analyzed for allelism, genetic heterogeneity, mosaicism, uniparental disomy or imprinting. Isolation of these genes will be important for accurate diagnosis and identification of genetic factors involved in cranial development.
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