Estruturação gênica e ancestralidade da população brasileira: estudo da população nativa da Ilha de Marajó com o emprego de marcadores de DNA

Abstract

Brazilian population is considered highly admixed and different patterns of the mixture between European, African and Native-american ancestry can be observed across the country. Predominance of European ancestry, more pronounced in the South and Southeast regions, followed by African ancestry, in greater proportion in the northeast, and finally the native component, more evident in the North region, have been demonstrated through data from autosomal and lineage markers. The Island of Marajó is in the north of Pará state, Northern Brazil. At the time of Portuguese colonization, it is believed that 30 different indigenous groups inhabited the Island.Currently it is composed by an admixed population, as a result of interethnic mating between European colonizers, Native Americans and African slaves. To investigate the genetic background of the Marajó population, a sample of unrelated individuals was selected, with matrilineal and / or patrilineal local ancestry for at least three generations. A total of 97 males were genotyped for the 27 Y chromosome STR included in the Yfiler Plus kit and 47 Y-SNPs. Additionally, 101 samples were sequenced for the complete mtDNA control region and 160 were genotyped for 46 autosomal insertion-deletion ancestry informative markers in a single multiplex reaction.The haplotype diversities obtained for Y-chromosome and mtDNA markers are lower (0.9959 and 0,9897, respectively) when compared with other Brazilian admixed populations, probably due to the geographic isolation of the island. The mtDNA haplogroup composition revealed a high contribution of Native American maternal ancestry of approximately 63 %, followed by 36 % of African haplogroups and only 1 % where from European origin. Conversely, 71% of male haplogroups, defined by Y-SNPs, were of European origin, 17 % sub-Saharan African and Native American ancestry was responsible for 12 %. In the study of the autosomal ancestry of the individuals, a 40,3 % of Native American ancestry was found, followed by 35.4 % of European and 24,3 % of African contributions. These values are close to the mean values for uniparental markers in this population, indicating a low influx of recent European ancestry within three generations. The results obtained will allow the creation of a database for the admixed population of Ilha de Marajó, this being the first time that the genetic ancestry profile of this population has been evaluated