Ethnic Heterogeneity of the North-swedish Population

ETHNIC HETEROGENEITY OF THE NORTH-SWEDISH POPULATION Its origin and medical consequences Per-Olof Nylander, Department o f Medical Genetics, University ofUmeât Umeå, Sweden Northern Sweden shows a unique population structure with remarkable geographical variations in the distribution of genetic disorders as well as genetic markers like blood groups, serum groups and red cell enzyme types. The present-day population of northern Sweden is a mixture of people of Finnish, Saamish (Lappish) and Central-Swedish origin. In this thesis the ethnic heterogeneity of the North-Swedish population (counties of Väster­ botten and Norrbotten) was studied using genetic blood markers, and the epidemiological impact of the ethnic heterogeneity was exemplified by studying the geographical correlation between Finnish admixture and risk factors for cardiovascular diseases. The following results were found: 1 Two new ethnic marker genes were discovered: the GC*1F allele (GC serum groups) for Saamish influence and the TF*C3 allele (transferrin serum groups) for Finnish influence. 2 Regional gene frequency variations in the A1A2B0 blood groups, 6-phosphogluconate dehydrogenase (6-PGD) types and transferrin and GC serum groups were studied in a sample of 4100-5600 individuals from northern Sweden distributed according to birth place into 23 subpopulations. A significant regional heterogeneity was found in all systems. The ethnic marker genes (AB0*A2, GC*1F, TF*C3, PGD*C) showed clineal variations consistent with the expected patterns of Finnish and Saamish admixture. 3 Finnish and Saamish admixture was estimated in the 23 subpopulations using AB0*A2, GC*1F and PGD*C as Saamish markers and TF*C3, TF*DCHI, TF*B0-1 and SODI*2 as Finnish markers. The Saamish admixture varied between 0 and 34% and was strongest in the northern and northwestern parts of northern Sweden. The Finnish influence varied between 0 and 84% and was strongest in the northern and northeastern parts of the area. The ethnic marker genes showed significant geographical intercorrelations. 4 Hypercholesterolemia showed a significant heterogeneity between the 23 subpopulations, and there was a significant geographical covariation with the degree of Finnish admixture. These results are consistent with the hypothesis that Finnish genetic influence may contribute to the development of hypercholesterolemia and thereby to the increased rate of cardiovascular diseases found in northern Sweden. The results of this study suggest that in addition to the founder effect ethnic heterogeneity is an important determinant of the structure of the North-Swedish population.