High-resolution physical and genetic mapping of the critical region for Meckel syndrome and Mulibrey Nanism on chromosome 17q22-q23

Previously, we assigned the genes For two autosomal recessive disorders, Me ckel syndrome (MKS; MIM 249000) and Mulibrey Nanism [MUL (muscle-liver-brai n-eye Nanism) MIM 253250] that are enriched in the Finnish population, to o verlapping genomic regions on chromosome 17q. Now, we report the constructi on of a bacterial clone contig over the critical region for both disorders. Several novel CA-repeat markers were isolated from these clones, which all owed refined mapping of the MKS and MUL loci using haplotype and linkage di sequilibrium analysis. The localization of the MKS locus was narrowed to <1 cM between markers D17S1290 and 132-CA, within an similar to 800-kb region . The MUL locus was refined into an similar to 1400-kb interval between mar kers D17S1290 and 52-CA. The whole MKS region falls within the MUL region. In the common critical region, the conserved haplotypes were different in M KS and MUL patients. A trancript map was constructed by assigning expressed sequence tags (ESTs) and genes, derived from the human gene map, to the ba cterial clone contig. Altogether, four genes and a total of 20 ESTs were pr ecisely localized. These data provide the molecular tools for the final ide ntification of the MKS and the MUL genes.