Genetic variation in Bulgarians: a mitochondrial DNA perspective

The structure and diversity of the Bulgarian mitochondrial DNA (mtDNA) gene pool is still almost unknown. In the present study, we have evaluated the extent and nature of mtDNA variation in a very large sample of Bulgarians, comprising 855 healthy unrelated subjects from across the country. The analysis was performed by sequencing about 850 base pairs (from np 16000 to np 250) of the mtDNA control region, followed by the hierarchical RFLP survey of numerous diagnostic coding-region markers. Overall, this approach allowed the identification of 586 different haplotypes and their classification into 79 known haplogroups or paragroups. The observed pattern of mtDNA diversity in Bulgarians is mainly shaped by haplogroups (H and U) dated to the Upper Paleolithic period. The spread of majority of the subclades of these haplogroups is related with waves of post-LGM recolonization. A fraction of the Bulgarian mtDNA gene pool is allocated to haplogroups, which represent Neolithic genetic component. In the comparisons of the observed haplogroup frequencies with those from a wide range of western Eurasian populations, Bulgarians do not group with the great majority of other Europeans and differ substantially from Near Eastern populations. This reflects the peculiarity of the Bulgarian mtDNA gene pool, determined by its history and demographic processes.