Inference on the biological history of the Comoros archipelago using the CD4 Alu/STR compound system

Abstract

The Comoros Archipelago is located at the northern end of the Mozambique Channel between Madagascar and the East African coast. Its settlement would have been influenced by contacts and possibly migratory waves that would have come from the East African coast, Middle East and Southeast Asia. This finding was the conclusion of various previous genetic studies carried out on Comorian populations to answer the question of its settlement and its biological history. These studies have used many kinds of molecular markers, although the autosomal markers (Alu/STR CD4) used in the present study have never been studied on the archipelago's populations. Nevertheless, they have been used on populations all over the world and have provided valuable information on genetic affinities and differentiation between populations and have also shed more light on the origins of modern human.In this study, we aimed to characterize for the first time the populations of the 3 main islands of the Comoros Archipelago using the CD4 Alu/STR compound system. Due to its robustness, this system allowed us to include, in our comparative analyses, populations having shared a common history with Comoros islanders (through migrations, commercial relations, or others).Our results showed by island, peculiar frequencies of STR and Alu alleles, as well as haplotypic ones. Genetic diversity values at the allelic level, ranged between 0.798 and 0.836 for the STR, and between 0.254 and 0.327 for the Alu. The most frequent haplotypes were 85+, followed by 115+ and 120+ in all the three islands. Phylogenetic and comparative analyses highlighted that our populations exhibit more affinities with sub-Saharan populations especially the Kenyans. However some Middle Eastern signals are perceptible in Anjouan Islanders through 90+ and 110− haplotypes.Finally, the results obtained contribute to a further understanding of the biological history of the Comoros population and provide new insights into the gene flows such as haplotypes of Middle Eastern origin.