Document Type

Brief Communication


The joint distributions of phenotypes from the apolipoprotein E gene (APOE) and from a closely linked restriction site polymorphism at the apolipoprotein C l locus {APOCl) were studied in population samples from Portugal and Sao Tome e Principe (Gulf of Guinea), a former Portuguese colony that was originally populated by slaves imported from the African mainland. The frequencies of the APOE alleles (*2, *3, and *4) in Portugal and Sao Tome fitted the ranges of variation generally observed in European and African populations, respectively. Haplotype analysis showed that in both populations the strength of linkage disequilibrium was highest for the APOE*2 allele and lowest for the APOE*4 allele, suggesting that the origin of the APOE alleles followed a 4 —> 3 —> 2 pathway and thus providing independent confirmation of the results from sequence homology studies with nonhuman primates. In accordance with global trends in the distribution of human genetic variation, the European sample from Portugal presented more intense linkage disequilibrium between APOE and APOCl than the African sample from Sao Tome where, despite the short 4-kb distance that separates the 2 loci, the level of association between the APOCl alleles and APOE*4 was nonsignificant.