Evidence for population sub‐structuring in São Tomé e Príncipe as inferred from Y‐chromosome STR analysis

Abstract

Seven Y‐chromosome STR loci, DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392 and DYS393 have been analysed in population samples of Angolares, Forros and Tongas, three ethnic groups from the African archipelago of São Tomé e Príncipe (Gulf of Guinea). Complete typings were obtained for 103 chromosomes, which belonged to 79 different haplotypes. The mean heterozygosity per locus in the overall São Tomean sample was 0.566, with the highest value found among Forros and the lowest among Angolares. Angolares also showed the lowest level of haplotype diversity. On average, the mean pairwise difference between two random haplotypes from Angolares, Forros and Tongas was 4.69, 6.74 and 6.23 repeats, respectively. The genetic distances were found to be statistically significant between Angolares and Forros or Tongas. In accordance, AMOVA revealed that the percentage of variation attributable to differences among groups was only significant when we distinguished between Angolares and non‐Angolares. Globally, these results indicate that, with respect to the pool of male lineages of São Tomé e Príncipe, some genetic sub‐structuring does exist, basically determined by the Angolares ethnic group.

Pattern of mtDNA Variation in Three Populations from São Tomé e Príncipe

“…The results here obtained with mtDNA are in full agreement with those previously derived from Y-STRs haplotypes (Trovoada et al 2001), and reinforce the depiction of genetic affinities between the three São Tomean ethnic groups as previously outlined.…”

“…This finding contrasts with that find using other genomic regions. In a previous study (Trovoada et al 2001) we detected some Y-chromosome haplotypes (defined by microsatellite loci) of likely European ancestry. Recently, Tomás et al (2002), using autosomal markers, estimated the European genetic contribution in São Tomé e Príncipe as 10.7%, although the value dropped to 6.5% when individuals with recent European ancestry were removed from the analysis.…”

“…The origin of the Angolares is less clear, notwithstanding the fact that their identification as a distinct community has strong support from their geographical confinement to the southeastern tip of São Tomé, from their cultural and livelihood traditions, and even from their own language, one of the most important badges of population identity. In a previous study (Trovoada et al 2001) we analysed Y-chromosome STRs in order to investigate the malemediated relationships among these three ethnic groups, and the genetic structure of São Tomé e Príncipe. We detected signs of a slight genetic microdifferentiation of Angolares comparative to the other two groups.…”

Insights from pattern of mtDNA variation into the genetic history of São Tomé e Prı́ncipe

“…1) belonging to 32 distinct haplogroups all specific from sub-Sahara, which testifies a full matrilineal African background. Previously we have detected some Y-STR haplotypes of likely European ancestry [3]. The combined results indicate that the European component of present São Tomé e Príncipe population was essentially mediated by males, signalling therefore the biased mating pattern that has prevailed in the archipelago.…”

Polimorfismos genéticos de ESD, GLO1, GPT e PGM1 em São Tomé e Príncipe

“…A análise baseada em frequências alélicas do tipo de marcadores estudados, tem-se afigurado pouco informativa para evidenciar pequenas misturas po pulacionais. Porém, um estudo mais recente da população Sãotomense re ferente a polimorfismos do cromossoma Y (Trovoada et al, 2001) …”