Purging of deleterious variants due to drift and founder effect in Italian populations with extended autozygosity

Purging through inbreeding occurs when consanguineous marriages increases the rate at which deleterious alleles are present in a homozygous state. In this study we carried out low-read depth (4-10x) whole-genome sequencing in 568 individuals from three Italian founder populations, and compared it to data from other Italian and European populations from the 1000 Genomes Project. We show extended consanguinity and depletion of homozygous genotypes at potentially detrimental sites in the founder populations compared to outbred populations. However these patterns are not compatible with the hypothesis of consanguinity driving the purging of highly deleterious mutations according to simulations. Therefore we conclude that genetic drift and the founder effect should be responsible for the observed purging of deleterious variants.