Variability of Linkage Disequilibrium (LD) among Corsican populations

Genetic isolates with a history of a small founder population, long-lasting isolation and population bottlenecks represent exceptional resources in the identification of genes involved in the pathogenesis of multifactorial diseases. In these populations the disease allele reveals Linkage Disequilibrium (LD) with markers over significant genetic intervals, therefore facilitating disease locus identification. This study has been designed to examine the background LD extension in some sub-populations of Corsica. Our interest in the island of Corsica is due to its geographical and genetic proximity to the other Mediterranean island of Sardinia. Sardinian isolates in which the extension of the background Linkage Disequilibrium is particularly high have been recently identified and are now the object of studies aimed towards the mapping of genes involved in complex diseases. Recent evidence have highlighted the genetic proximity between the populations of Corsica and Sardinia. Given these considerations, Sardinia and Corsica may represent a unique system to carry out parallel association studies whose results could be validated by comparison. In the present study, we have analyzed the LD extension on the Xq13.3 genomic region in four subpopulations of Corsica: Corte, Niolo, Bozio, (located in the mountainous north-center of the island) and Ajaccio (located in the south west of the island in a stretch of coast area). Our results show a strong degree of LD over long distance for the population of Bozio and to a less extent for the population of Niolo. Their LD extent is comparable or higher to that reported for other isolates. In contrast the population of Ajaccio shows a very low degree of LD while the population of Corte shows intermediate values.