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In this paper, we carry out a combined analysis of autosomal (ten microsatellites and an Alu insertion), mitochondrial (HVR-1 sequence, 360 nucleotides) and Y-chromosomal (seven microsatellites) variation in the Mbenzele Pygmies from the Central African Republic. This study focuses on two important questions concerning the admixture and origin of African Pygmies. Ethnographic observations suggest a sex-biased gene flow between the Bantus and Pygmies, an issue which could be clarified through genetic analyses may shed light. A study of intrapopulational variation of mtDNA and Y-chromosome produces results in accordance with the hypothesized matrimonial behaviour. In fact, while shared mitochondrial haplotypes belonging to the L1c5 (or L1c1a1 clade) sub-haplogroup provides evidence of a Pygmy-to-Bantu female biased gene flow, a male biased gene flow from Bantu to Pygmies is supported by the distribution of the Y-chromosomes bearing M2 mutation. The second part of our study regards the question of the genetic relationships between Western and Eastern Pygmies. Our results favour the pre-Bantu hypothesis which suggests that the two Pygmy groups separated in ancient times (at least 18,000 years ago), whereas they do not support the recent divergence and differential admixture hypothesis which posits their separation as a consequence of the Bantu expansion (2,000-3,000 years ago).

This study analyzes the variation of six binary polymorphisms and six microsatellites in the Mbenzele Pygmies from the Central African Republic. Five different haplogroups (B2b, E(xE3a), E3a, P and BR(xB2b,DE,P)) were observed, with frequencies ranging from 0.022 (haplogroup P) to 0.609 (haplogroup E3a). A comparison of haplogroup frequencies indicates a close genetic affinity between the Mbenzele and the Biaka Pygmies, a finding consistent with the common origin and the geographical proximity of the two populations. The haplogroups P, BR(xB2b,DE,P) and E(xE3a), which are rare in sub-Saharan Africa but common in western Eurasia, were observed with frequencies ranging from 0.022 (haplogroup P) to 0.087 (haplogroup E(xE3a)). Thirty different microsatellite haplotypes were detected, with frequencies ranging from 0.022 to 0.152. The Mbenzele share the highest percent of microsatellite haplotypes with the Biaka Pygmies. Five out seven haplotypes which are shared by the Mbenzele and Biaka Pygmies belong to haplogroup E3a, which suggests that they are of Bantu origin. The plot based on F(st) genetic distances calculated using microsatellite data provides a picture of population relationships which is in part congruent and in part complementary to that obtained using haplogroup frequencies. Finally, the Mbenzele and Biaka Pygmies were found to be markedly more genetically similar using Y-chromosomal than autosomal microsatellites. We suggest that this could be due to the higher phylogenetic stability of Y-chromosome and to the effect of the male-biased gene flow during the Bantu expansion., (Copyright 2003 Wiley-Liss, Inc.)

Ten protein coding loci (6-PGD, A1-AT, ACP1, CaII, ESD, GC, GPX1, Hb beta, PGM1, and TF) were analyzed in the Mbenzele Pygmies from the Central African Republic. The frequency data were used to calculate the genetic distances between Mbenzele Pygmies and other African groups. In the principal coordinate plot of FST genetic distances, the Mbenzele cluster together with other Pygmies of the western cluster, the Biaka from C.A.R., Gielli from Cameroon, and Babinga from Congo. By contrast, they are considerably distanced from other Pygmy groups of the eastern cluster (Twa from Rwanda, Mbuti from Zaire). Genetic distances obtained using protein loci were compared with those based on microsatellite loci. The two distance matrices are insignificantly correlated (r = 0.268; one tail probability = 0.332), and the main difference is in the higher genetic affinity between the Mbenzele and Biaka Pygmies observed at the protein level. Although reasons underlying the discrepancy between inter-populational variation at protein and DNA loci are not established with certainty, the comparison suggests that the genetic distance between the Mbenzele and Biaka Pygmies at microsatellite loci could have been shaped by genetic drift.

Phenotype and allele frequencies for hemoglobin types (Hb beta), acid phosphatase (AcP), phosphoglucomutase (PGM1 and PGM2), esterase D (EsD), 6-phosphogluconate dehydrogenase (6-PGD), glyoxalase I (GLO), superoxide dismutase (SOD A), and adenylate kinase (AK) as well as for haptoglobins (Hp), group-specific component (Gc), transferrin (Tf), Gm, and Inv groups and albumin, are reported in the Mbugu, Sango, Yakpa, and Baya Mandja ethnic groups in the Basse Kotto district of the Central African Republic. The total sample size amounts to 133 males and 128 females aged from 16 to 60, unrelated and healthy. A new albumin variant (albumin Mbugu) is described and discussed. The average heterozygosity is high in each group because of a high degree of exogamy. the FST average standardized value among the four groups indicates that the genetic differentiation in Basse Kotto is at level of about 2%. This indicates that the four examined groups might be considered genetically homogeneous, in spite of their different ethnic origins. The genetic distances among the four groups show that only the Baya Mandja are less closely related to the other three groups because of their foreign origin.

Phenotype and allele frequencies for erythrocyte glutathione peroxidase (GPX1) polymorphism are reported in the Mbugu and Sango (Central African Republic), Goun (Benin), and Bamileke (Cameroon) ethnic groups. The GPX1*2 allele frequencies (from 0.012 in the Sango to 0.058 in the Bamileke) fit into the range of the data already known for the Subsaharan populations. The value of GPX1*2 for study of the genetic admixture between Negro and Pygmy populations is suggested. Three different unusual GPX1 electrotypes are described. Finally, we hypothesize an interaction between GPX1*2 and Hb beta*S allelic products occurring in the sickle cells infected by Plasmodium falciparum.

Phenotype and gene frequencies of four blood group polymorphisms (ABO, MNSs, Rhesus, and Duffy) as well as hemoglobin types of four populations of the Republic of Central Africa are reported. All these polymorphisms are in Hardy-Weinberg equilibrium. Regarding the four blood group polymorphisms mentioned above the genetic distances according to NEI have been computed for fifteen populations of the Central-Eastern and Central-Western areas of Africa, including the four own samples. The results of these analyses are discussed.

PGM1 and CAII polymorphisms were studied in four population samples of the Central African Republic (Mbugu and Sango) and of Benin (Goun and Nago). The results are compared with those reported on other African populations.