Microsatellite variation in Central Africa: An analysis of intrapopulational and interpopulational genetic diversity

Abstract

As a part of a research project on molecular variation in Central Africa, we have analyzed 10 microsatellites (CD4, CSFO, D3S1358, D18S51, D21S11, F13A1, FES, TH01, TPOX, and VWA) in the Bamileke and Ewondo from Cameroon and the Sanga and Mbenzele Pygmies from the Central African Republic (a total of 390 chromosomes). A statistically significant trend towards heterozygote deficiency was detected in the Mbenzele Pygmies. This was established through the use of powerful exact tests for the Hardy-Weinberg equilibrium. A certain degree of isolation and a small effective size may explain this finding. However, the lack of any substantial reduction in allelic diversity in the Mbenzele does not support the possibility that this group has a smaller effective size in evolutionary terms. A possible explanation based on ethnographic studies suggests that the gene flow from non-Pygmies to Pygmies could have been interrupted only in relatively recent times. The analysis of association between genotypes at pairs of independent loci indicates that the level of subheterogeneity is markedly lower in the Bamileke than in other sampled populations. This may be explained by the combined effect of larger population size, more rigid respect of clanic exogamy, and higher matrimonial mobility of the Bamileke. Finally, we have analyzed interpopulational relationships among our sampled populations and other Central African populations. The results are consistent with a previous study of protein loci (Spedini et al. 1999), which suggests the recent history of the Bamileke and Ewondo has led them to aquire a substantial genetic similarity. Furthermore, the Mbenzele Pygmies diverge from Biaka Pygmies, despite their common origin and geographical proximity. This is probably due to the differentiating effect of genetic drift, which is enhanced by the small effective size of Pygmy populations.

Microsatellite studies on an isolated population of African descent in the Brazilian state of Bahia

“…When compared to other populations, it was found that *16 is the most frequent vWA allele in Africans and African-Americans (0.261 to 0.371; Destro-Bisol et al, 2000). In the African descendant population of São Gonçalo, Bahia (Sousa, 2001) the allele *16 was also the most frequent (0.286).…”

“…There were no individuals classified as Amerindian or Caucasian by phenotype in this commuStudies in an African-descendant isolate 25 Sources: (1) Africans - (Deka et al, 1999;Destro-Bisol et al, 2000;Huguet et al, 1998;Bosh et al, 2001;Gene et al, 2001;Alves et al, 2001;Brinkmann et al, 1996;Brinkmann et al, 1998;Rolf et al, 1998;Wang et al, 2002;Pérez-Lezaun et al, 1997;Yunis et al, 2000;Corte-Real et al, 2000;Dios et al, 1998); (2) Europeans (Pérez- Lezaun et al, 2000;Anjos et al, 2000;Lourdes-Pontes et al, 1998;Asmundo et al, 1998;Santos et al, 1996;Souto et al, 1996, Souto et al, 1998Alves et al, 2001;Pinheiro et al, 1996;Amorim et al, 1996;Pereira et al, 1996;Gusmão et al, 1997;Espinheira et al, 1996;Miranda et al, 1998;Prata et al, 1998) nity. This date on phenotypic ethnic classification is based on facial morphological characteristics and skin color in body regions not exposed to the sun (Azevêdo, 1980).…”

“…For the F13A1 locus, the *5 allele was the most frequent in the Bananal (0.333) and Jequié (0.270) samples, this allele also being common in African-Americans (0.342) and Africans (0.337 to 0.500; Destro-Bisol et al, 2000).…”

“…The second most common allele in Bananal (*11; 0.255) was the most frequent FES/FPS allele in Jequié (0.362), African-Americans (0.355) and Africans (0.359 to 0.414; Destro-Bisol et al, 2000).…”

A comprehensive analysis of microsatellite diversity in Aboriginal Australians

“…Several studies have shown, however, that when a reasonably large number of microsatellites are scored the inferences from those samples, even at the worldwide level, are sound (Bowcock et al 1994;Jorde et al 2000;Rosenberg et al 2002;Ayub et al 2003;Zhivotovsky et al 2003;Shepard et al 2005;Zabala Fernandez et al 2005). For examining structure and variation within a single population or ethnic group they may be the marker of choice Destro-Bisol et al 2000;Perez-Miranda et al 2005;Li et al 2006). This study of structure and variation among Australian Aboriginals using fifteen autosomal microsatellites fulfils these requirements.…”