Clinical immunology
Road-like pattern of HLA-ABDR-based genetic distances between populations

Genetic distances between populations may indicate the optimal direction of hematopoietic stem cell donor search. In some extent straight-line spatial geographic distances are similar to genetic distances. We tested the hypothesis that natural barriers, such as mountains, water reservoirs, desert and permafrost areas can change simple correlation between geography and genetics. We typed 200 healthy individuals of Polish population in HLA-A, B and DRB1 at the allelic level and compared allele group frequencies with 38 world populations. Standard Nei’s pairwise genetic distances were estimated and correlated with land road distances in kilometres and straight-line spatial geographic distances. The genetic distances between all 39 populations were highly correlated with road distances (r=0.499, P=0.0012, df. =37).
The correlation was much higher when estimation was limited to non-admixed and non-transferred populations (ie. when African American 1998, African American 2007, Argentina Buenos Aires, Belgian Total and Turkish minority in Germany, have been removed) (r=0.831, P=1,2E-09, df.=32). Simultaneously the straight-line spatial geographic distances correlated with genetic distances even higher (r=0.699, P=7.3E-07, df.=32 and r=0.848, P=2.4E-10, df.=32, respectively, for all 39 and 34 non-admixed/non-transferred populations). The preliminary analysis of a limited number of populations (N=20) has shown that the straight-line geographic spatial distances correlated with genetic distances much less than road distances (r=0.442, P=0.051, df.=18 vs. r=0.550, P=0.012, df.=18, respectively for straight-line and road distances). Simultaneously, geographic-like pattern of gene frequency low dimensional correspondence analysis was displayed in three dimensional projection. These results confirm considerable dependence of genetic and geographic distances. The results support the hypothesis that natural gene spread-out must have been more similar to waves and water circle-like propagation than to journeys along single paths. Natural barriers such as water reservoirs and mountains have had limited influence.