LINKAGE MAPPING BY SIMULTANEOUS SCREENING OF MULTIPLE POLYMORPHIC LOCI USING ALU OLIGONUCLEOTIDE-DIRECTED PCR

We present the use of our recently described multiple-loci polymorphic DNA markers ("alumorphs") for linkage mapping of the human genome. By using the polymerase chain reaction (PCR) with an Alu-specific primer we could reveal, in a single experiment, up to 20 genomic polymorphisms seen as the presence or absence of amplified DNA fragments originating from genomic segments flanked by Alu repeats. Using this approach we examined genomic DNA samples from two families with a history of pseudovitamin D-deficiency rickets (PDDR), an autosomal recessive disorder. An indication of linkage with the PDDR phenotype was found for one of the polymorphic bands, denoted 30A. A significant linkage [logarithm-of-odds (lod) score > 3.0] was obtained between this polymorphism and a number of chromosome 12q markers tightly linked to PDDR. The 30A band specifically hybridized to DNA digests from hybrid cell lines carrying a human chromosome 12, thus independently assigning the 30A marker to this chromosome. Since Alu elements are ubiquitous in human DNA, the use of alternative Alu-specific primers, which reveal different sets of Alu-flanked loci, should provide an efficient and rapid approach to human genetic mapping.