Sunday, August 17, 2008

flipping inversion

A new paper, just out in Nature Genetics, by Zody and Jiang et al. looks at the evolutionary history of the ~1Mb 17q inversion. This inversion was first described by Stefansson et al.. Stefansson et al. found the normal allele H1 was present in many populations but that the inverted allele H2, seemed to have increased rapidly in frequency in Europeans, perhaps due to positive selection, in support of this they found that the inverted allele H2 was associated with a higher birth-rate in modern day individuals in Iceland. Further sequence analysis by Stefansson et al. suggested that the two alleles (H1 and H2) diverged ~2.5-3 million years ago, which is old for a human allele and surprising given the low frequency of H2 in Africa. Since then the region has been implicated in various diseases. Zody and Jiang et al. reconstruct the history of the region and surprisingly suggest that the H2 allele is actually the ancestral state, despite the fact that it is present at low frequency world-wide. They also find that the similar inversions are polymorphic in chimpanzee and orangutan, suggesting that the region is subject to recurrent inversions.

Evolutionary toggling of the MAPT 17q21.31 inversion region.
Zody and Jiang et al.
Nature Genetics

A common inversion under selection in Europeans.
Stefansson et al.
Nature Genetics

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