It is well demonstrated that the frequency of sickle cell allele, HBB*S, reaches the highest values in regions of endemic malaria, due to resistance to the malaria infection conferred by HBB*S. Its presence in Portugal has been explained as the consequence of past population migrations, which in part also explain the uneven distribution of HBB*S across the country, where it tends to increase in frequency from the north towards the south-central regions.
In order to better understand how HBB*S was introduced in Portugal, the screening of HBB was performed in 266 individuals from Alentejo (Coruche, Serpa (Pias) and Alcácer do Sal). Then, to further infer the origin of the detected HBB*S chromosomes, their haplotypic background, encompassing the entire cluster of β-globin genes, was examined through a SNaPshot® Multiplex system that was purposely implemented as an alternative to the conventional RFLP-based method, and that allowed to interrogate the most informative positions defining the HBB*S haplotypes.
19 individuals harboured the c.20A>T mutation that underlies HBB*S, whose frequency was 2.2, 2.9 and 7.7% in Coruche, Alcácer do Sal and Serpa, respectively. The last value is the highest up to now reported in the country, where foci of high prevalence of HBB*S carriers have been previously identified in south regions.
Among the chromosomes bearing HBB*S, 29% harboured the Benin haplotype, 13.1% the Senegal and 10.5% the Bantu. Remarkably, whereas in Alcáçer do Sal and Coruche only Senegal and Bantu haplotypes were found, in Serpa all haplotypes were Benin.
Taking into account the global distribution of HBB*S haplotypes, the findings obtained reinforce a scenario before proposed positing that the introduction of HBB*S in south Portugal was mediated by gene influx events with distinct sources: one from the region encompassing the Mediterranean basin (captured by the Benin haplotype), and other from sub-Saharan Africa, likely afforded by the transatlantic slave trade (captured by the Senegal and Bantu haplotypes).info:eu-repo/semantics/publishedVersio
