Introducing the Algerian mitochondrial DNA and Y-chromosome profiles into the North African landscape

Abstract

North Africa is considered a distinct geographic and ethnic entity within Africa. Although modern humans originated in this Continent, studies of mitochondrial DNA (mtDNA) and Y-chromosome genealogical markers provide evidence that the North African gene pool has been shaped by the back-migration of several Eurasian lineages in Paleolithic and Neolithic times. More recent influences from sub-Saharan Africa and Mediterranean Europe are also evident. The presence of East-West and North-South haplogroup frequency gradients strongly reinforces the genetic complexity of this region. However, this genetic scenario is beset with a notable gap, which is the lack of consistent information for Algeria, the largest country in the Maghreb. To fill this gap, we analyzed a sample of 240 unrelated subjects from a northwest Algeria cosmopolitan population using mtDNA sequences and Y-chromosome biallelic polymorphisms, focusing on the fine dissection of haplogroups E and R, which are the most prevalent in North Africa and Europe respectively. The Eurasian component in Algeria reached 80% for mtDNA and 90% for Y-chromosome. However, within them, the North African genetic component for mtDNA (U6 and M1; 20%) is significantly smaller than the paternal (E-M81 and E-V65; 70%). The unexpected presence of the European-derived Y-chromosome lineages R-M412, R-S116, R-U152 and R-M529 in Algeria and the rest of the Maghreb could be the counterparts of the mtDNA H1, H3 and V subgroups, pointing to direct maritime contacts between the European and North African sides of the western Mediterranean. Female influx of sub-Saharan Africans into Algeria (20%) is also significantly greater than the male (10%). In spite of these sexual asymmetries, the Algerian uniparental profiles faithfully correlate between each other and with the geography.

Figure 1. Simplified phylogenetic trees for Y-chromosome sub-haplogroups.

A) E-M78 and B) M-R343.

Figure 2. Graphical relationships among the studied populations.

PCA plots based on mtDNA (a) and Y-chromosome (b) polymorphism. Codes are as in Supplementary Tables S2 and S6.

Figure 3. Reduced median network relating HVS-1 sequences of subhaplogroup M1.

The central motif (haplotype HT1) differs from rCRS , at position 16129 16189 16223 16249 16311. Population codes as in Supplementary Table S2. Numbers along links refer to nucleotide positions minus 16000; suffix indicates a transversion. Black circles correspond to haplotypes observed in Algeria, whereas grey triangles pentagons correspond to lineages found in Egypt. Haplotype observed both in Algeria and Egypt are indicated using a black triangle. Grey circles indicate haplotypes observed in other geographical regions. Size of boxes is proportional to the number of individuals included. HT1 = 13 ALG, 17 ARP, 2 BAL, 8 EGY, 5 IP, 5 ISS, 2 LIB, 18 MOR, 13 TUN, TuAn; HT2 = 6 ALG, ARP, BAL, IRN, LEQ, 2 LIB, 3 MOR, SAM, 2 TUN; HT3 = 2 ALG, ARP, LEQ, 2 MOR; HT4 = 3 ALG, 2 EGY, 3 IP, 2MOR; HT5 = 14 ARP, 3 BAL, 3 CAU, 10 EGY, 4 IP, IRN, 7 ISS, 4 LEQ, 2 LIB, 6 MOR; HT6 = ARP, 16 EGY.