January 14, 2013

Haplotype of Neandertal origin in OAS gene cluster in Eurasians

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Mol Biol Evol (2013) doi: 10.1093/molbev/mst004

Neandertal origin of genetic variation at the cluster of OAS immunity genes

Fernando L. Mendez et al.

Analyses of ancient DNA from extinct humans reveal signals of at least two independent hybridization events in the history of non-African populations. To date there are very few examples of specific genetic variants that have been rigorously identified as introgressive. Here we survey DNA sequence variation in the OAS gene cluster on chromosome 12 and provide strong evidence that a haplotype extending for ~185 kb introgressed from Neandertals. This haplotype is nearly restricted to Eurasians and is estimated to have diverged from the Neandertal sequence ~125 kya. Despite the potential for novel functional variation, the observed frequency of this haplotype is consistent with neutral introgression. This is the second locus in the human genome, after STAT2, carrying distinct haplotypes that appear to have introgressed separately from both Neandertals and Denisova.

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4 comments:

Luca said...

According to the paper the haplotype is restricted to Eurasians and is estimated to have diverged from the Neandertal sequence 125 kya.
How it is possibile if we still consider the "out of Africa" event not early than 100 kya?
I suppose something is missing to my understanding of the matter...

shenandoah said...

"How it is possibile if we still consider the "out of Africa" event not early than 100 kya?"

It's because Neanderthals are being treated by researchers as an "archaic" species (that's their operating premise, in other words). Problem is, they probably are not all that "archaic". Instead, what they probably are/were is a hybrid mixture of Homo Sapiens and Lower Primates (ie Apes or more probably Rhesus macaques). It is probably the Lower Primate factor(s) in the Neanderthal DNA which is giving geneticists that strange timeline (125 kya).

terryt said...

"they probably are not all that "archaic". Instead, what they probably are/were is a hybrid mixture of Homo Sapiens and Lower Primates (ie Apes or more probably Rhesus macaques)".

I think you're on your own with that idea.

"According to the paper the haplotype is restricted to Eurasians and is estimated to have diverged from the Neandertal sequence 125 kya.
How it is possibile if we still consider the 'out of Africa' event not early than 100 kya?"

One solution may be that it was already diverse when it introgressed. If that is the solution it would necessitate it having introgressed into modern humans many times, even extensively, though. An extensive hybridisation, not just a single event.

"This is the second locus in the human genome, after STAT2, carrying distinct haplotypes that appear to have introgressed separately from both Neandertals and Denisova".

And may just be the beginning of even more discoveries.

Raimo said...

It might be that 125k event represents a)divergence in Neanderthal populations, with only one of them eventually mating with modern humans b)results from a very minor contact between modern humans and Neanderthals or c)shows that a continued geneflow on very low level was happening in the areas where the species lived closest to each other at the moment. There's possible evidence of Neanderthal sea travels to Crete. Before 125k the sea level at Strait of Gibraltar was possibly little lower than now; on one shore were Neanderthals, on the other modern humans. Either us or them could have traveled over it.