January 11, 2008

Sardinian Y chromosomes

The open access journal PLoS One has an article on the Y chromosomes of Sardinians.

PLoS ONE. 2008 Jan 9;3(1):e1430.

Y-chromosome based evidence for pre-neolithic origin of the genetically homogeneous but diverse sardinian population: inference for association scans.

Contu D, Morelli L, Santoni F, Foster JW, Francalacci P, Cucca F.

Laboratorio di Immunogenetica, Ospedale Microcitemico, Cagliari, Italy.

The island of Sardinia shows a unique high incidence of several autoimmune diseases with multifactorial inheritance, particularly type 1 diabetes and multiple sclerosis. The prior knowledge of the genetic structure of this population is fundamental to establish the optimal design for association studies in these diseases. Previous work suggested that the Sardinians are a relatively homogenous population, but some reports were contradictory and data were largely based on variants subject to selection. For an unbiased assessment of genetic structure, we studied a combination of neutral Y-chromosome variants, 21 biallelic and 8 short tandem repeats (STRs) in 930 Sardinian males. We found a high degree of interindividual variation but a homogenous distribution of the detected variability in samples from three separate regions of the island. One haplogroup, I-M26, is rare or absent outside Sardinia and is very common (0.37 frequency) throughout the island, consistent with a founder effect. A Bayesian full likelihood analysis (BATWING) indicated that the time from the most recent common ancestor (TMRCA) of I-M26, was 21.0 (16.0-25.5) thousand years ago (KYA) and that the population began to expand 14.0 (7.8-22.0) KYA. These results suggest a largely pre-Neolithic settlement of the island with little subsequent gene flow from outside populations. Consequently, Sardinia is an especially attractive venue for case-control genome wide association scans in common multifactorial diseases. Concomitantly, the high degree of interindividual variation in the current population facilitates fine mapping efforts to pinpoint the aetiologic polymorphisms.



  1. I'm no expest on genetics, but as a Sardinian, I have to point out that the information here is incomplete. It is true that Sardinian population is generally homogenous, but probably an in-depth study would reveal that this high homegeneity is confined to the mountain regions, while the plains and coasts show a mugh higher variety. At least, that's what historical and linguistic research shows.

    Livia (from the coast, and with no hereditary diseases)

  2. Livia, unfortunately very few Sardinians are tested, but they would be very interesting genetically, above all for my theory of an Italian Refugium during the Younger Dryas, as what is in Sardinia was in Italy too, but Sardinia is extremely conservative, above all for R1b1a and the old R1b1c10, apart for I2-M26 and G massively present. There are in Sardinia some good geneticists (like my compatriot Francalacci), but I think their exams aren't so deep as those we do (deCODEme and 23andME).If you could find someone for testing (by SMGF it is with no expense),you would do a service for Genetics (and for me).

  3. Gioiello, if the test is free I'm sure it would be easy to find people for testing, but I can't figure out how to contact you.
    You can contact me at cases(at)tiscali(dot)it


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