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Wednesday, August 16, 2006

mtDNA Analysis in Sardinia

A new academic paper by Cristina Farumene et al., entitled High Resolution Analysis and Phylogenetic Network Construction Using Complete mtDNA Sequences in Sardinian Genetic Isolates, undertakes a novel look at the the mitochondrial DNA of three villages (Talana, Urzulei, and Perdasdefogu) in the Ogliastra region of Sardinia.

They reconstructed genealogical records of the towns, then undertook mtDNA samples of the living descendants of identified maternal "founders". Essentially, this amounts to an mtDNA snapshot of the towns in the 17th century. From the article's abstract:

For mitochondrial phylogenetic analysis, the best result comes from complete sequences. We therefore decided to sequenced the entire mtDNA (coding and D-loop regions) of 63 individuals selected in three small Ogliastra villages, an isolated area of eastern Sardinia: Talana, Urzulei and Perdasdefogu. We studied at least one individual for each of the most frequent maternal genealogical lineages belonging to haplogroups H, V, J, K, T, U and X. We found in our 63 samples, 172 and 69 sequence changes in the coding and in the D-loop region respectively. Thirteen out of 172 sequence changes in the coding region are novel. It is our hypothesis that some of them are characteristic of the Ogliastra region and/or Sardinia.

We reconstructed the phylogenetic network of the 63 complete mtDNA sequences for the three villages. We also drew a network including a large number of European sequences and calculated various indices of genetic diversity in Ogliastra. It appears that these small populations remained extremely isolated and genetically differentiated compared to other European populations. We also identified in our samples a never previously described subhaplogroup, U5b3, that seems peculiar to the Ogliastra region.

The paper is interesting, but of primary note for us is the high representation (more than 50%) of Haplogroup H. Two of the villages also had a lot of Haplogroup U (20-30%), but Perdasdefogu had almost none. On the other hand, Perdasdefogu had a good amount of K (19%) whereas the other two villages had none. And none of the villages had the level of Haplogroup T that we have in the Italy DNA Project.


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