The fine-scale genetic structure of the French population (preprint):
The existence of population stratification is a major problem in case-control association studies and there is a need for a better assessment of allele frequency variation within populations at all geographic scales. Such efforts have been conducted in different European countries where strong patterns of geographic variations were found. The genome-wide extent of variations in allele frequencies of common variants has however never been documented at the scale of France. In this study, we describe these patterns of variation using genome-wide SNP chip data from 4,433 individuals, recruited as part of the Three-City study and whose places of birth in France were available. We show that there is a strong correlation between the top three principal components extracted from the genetic data and the latitude and longitude of birth places. Using multiple linear regression models, we were able to determine the birth places within less than 197 km of the reported origin for 50% of the individuals. Using model-based clustering with seven main geographic regions, we found that individuals were assigned in majority to their true region of origin. However, we found that information on ancestry could not be retrieved by using a small panel of Ancestry-Informative Markers (AIMs).