Research of the origin of a particular Tunisian group using a physical marker and Alu insertion polymorphisms

Alu insertion polymorphisms in the African Sahel and the origin of Fulani pastoralists

BACKGROUND

The origin of Western African pastoralism, represented today by the Fulani nomads, has been a highly debated issue for the past decades, and has not yet been conclusively resolved.

AIM

This study focused on Alu polymorphisms in sedentary and nomadic populations across the African Sahel to investigate patterns of diversity that can complement the existing results and contribute to resolving issues concerning the origin of West African pastoralism.

SUBJECTS AND METHODS

A new dataset of 21 Alu biallelic markers covering a substantial part of the African Sahel has been analysed jointly with several published North African populations.

RESULTS

Interestingly, with regard to Alu variation, the relationship of Fulani pastoralists to North Africans is not as evident as was earlier revealed by studies of uniparental loci such as mtDNA and NRY. Alu insertions point rather to an affinity of Fulani pastoralists to Eastern Africans also leading a pastoral lifestyle.

CONCLUSIONS

It is suggested that contemporary Fulani pastoralists might be descendants of an ancestral Eastern African population that, while crossing the Sahara in the Holocene, admixed slightly with a population of Eurasian (as evidenced by uniparental polymorphisms) ancestry. It seems that, in the Fulani pastoralists, Alu elements reflect more ancient genetic relationships than do uniparental genetic systems.

(C)ce(s) haplotype screening in Tunisian blood donors

BACKGROUND

The (C)ce(s) haplotype, mainly found in black individuals, contains two altered genes: a hybrid RHD-CE-D(s) gene segregated with a ce(s) allele of RHCE with two single nucleotide polymorphisms, c. 733C>G (p.Leu245Val) in exon 5 and c. 1006G>T (Gly336Cys) in exon 7. This haplotype could be responsible for false positive genotyping results in RhD-negative individuals and at a homozygous level lead to the loss of a high incidence antigen RH34. The aim of this study was to screen for the (C)ce(s) haplotype in Tunisian blood donors, given its clinico-biological importance.

MATERIAL AND METHODS

Blood samples were randomly collected from blood donors in the blood transfusion centre of Sousse (Tunisia). A total of 356 RhD-positive and 44 RhD-negative samples were tested for the (C)ce(s) haplotype using two allele-specific primer polymerase chain reactions that detect c. 733C>G (p.Leu245Val) and c. 1006G>T (p. Gly336Cys) substitutions in exon 5 and 7 of the RHCE gene. In addition, the presence of the D-CE hybrid exon 3 was evaluated using a sequence-specific primer polymerase chain reaction.

RESULTS

Among the 400 individuals only five exhibited the (C)ce(s) haplotype in heterozygosity, for a frequency of 0.625%. On the basis of the allele-specific primer polymerase chain reaction results, the difference in (C)ce(s) haplotype frequency was not statistically significant between RhD-positive and RhD-negative blood donors.

DISCUSSION

These data showed the presence of the (C)ce(s) haplotype at a low frequency (0.625%) compared to that among Africans in whom it is common. Nevertheless, the presence of RHD-CE-D(s) in Tunisians, even at a lower frequency, should be considered in the development of a molecular genotyping strategy for Rh genes, to ensure better management of the prevention of alloimmunisation.