DISTRIBUTION AND FREQUENCY OF A POLYMORPHIC ALU INSERTION AT THE PLASMINOGEN-ACTIVATOR LOCUS IN HUMANS

We have investigated the frequency distribution, across a broad range of geographically dispersed populations, of alleles of the polymorphic Alu insertion that occurs within the 8th intron of the tissue plasmin ogen activator gene (PLAT). This Alu is a member of a recently derived subfamily of Alu elements that has been expanding during human evolut ion and continues to be transpositionally active. We used a ''populati on tube'' approach to screen 10 chromosomes from each of 19 human popu lations for presence or absence of this Alu in the PLAT locus and foun d that all tested populations are dimorphic for presence/absence of th is insertion. We show that the previously published EcoRI, HincII, Pst I, TaqI, and XmnI polymorphisms at the PLAT locus all result from inse rtion of this Alu and we use both restriction fragment length polymorp hism and polymerase chain reaction analysis to examine the frequency o f Alu(+) and Alu(-) alleles in a sample of 1003 individuals from 27 hu man populations and in 38 nonhuman primates. Nonhuman primates are mon omorphic for the Alu(-) allele. Human populations differ substantially in allele frequency, and in several populations both alleles are comm on. Our results date the insertion event prior to the spread and diver sification of modem humans.