Inferring microevolutionary patterns from allele-size frequency distributions of minisatellite loci: a worldwide study of the APOB 3 ' hypervariable region polymorphism

The availability of numerous population and molecular data makes the apolip oprotein B 3' hypervariable region (APOB 3' HVR) polymorphism ideal for a p ilot study of the relationships between the allele-size frequency distribut ions (referred to as allele-size distributions) of minisatellite loci and t he microevolutionary processes underlying their present-day polymorphism in human populations. In this paper, we present a worldwide APOB 3' HVR study , based on published and unpublished data, which refers to 36 populations. We systematically compare APOB 3' HVR within-group diversity (in terms of h eterozygosity, number of alleles, and allele-size variance) in numerous hum an populations, including African, European, Asian, Amerindian, Australomel anesian, and Polynesian groups. Overall, our analyses indicate a greater AP OB 3' HVR diversity in Africans than non-Africans. Then, we compare APOB 3' HVR allele-size distributions. The RPOB 3' HVR allele-size distribution is found to be quasi-unimodal in Africans and bimodal or nonunimodal in non-A frican populations. The analysis of the distribution of pairwise comparison s suggests that Africans expanded earlier and/or that their ancestral popul ation was larger than other continental groups. As a final step, we examine APOB 3' HVR interpopulational relationships by using three genetic distanc es. The Fs, genetic distance, which assumes genetic drift as being the agen t that differentiates populations, provides results that are more congruent with established anthropological knowledge than mutation-based distances ( D-SW and R-ST). We hypothesize that the ancestral population was characteri zed by a high heterozygosity, an extended range of allele size, and a quasi -unimodal allele-size distribution centered on allele *37, features persist ing in examined African populations. Sampling processes during "out-of-Afri ca" migrations would be responsible for the decrease in APOB 3' HVR gene di versity and the nonunimodal allele-size distribution observed in non-Africa ns. Some possible confounding factors are discussed and a prospect of how t he hypothesis could be refined and tested is given.