Friday, October 28, 2016

Inuit Body Fat Gene Derived From Denisovans

A new pre-print finds that a gene that enhances selective fitness in Arctic Inuits related to body fat (which is protective in cold temperatures) has origins in the Denisovan genome. The only prior instance of likely selective fitness enhancing Denisovan introgression (of which I am aware) was of high altitude adaptation genes in Tibetans. Among other things, this suggests non-Melanesians experienced Denisovan introgression in the area where Denisovan remains were found, even if this ancestry was subsequently highly diluted.
A recent study conducted the first genome-wide scan for selection in Inuit from Greenland using SNP chip data. Here, we report that selection in the region with the second most extreme signal of positive selection in Greenlandic Inuit favored a deeply divergent haplotype that is closely related to the sequence in the Denisovan genome, and was likely introgressed from an archaic population. The region contains two genes, WARS2 and TBX15, and has previously been associated with adipose tissue differentiation and body-fat distribution in humans. We show that the adaptively introgressed allele has been under selection in a much larger geographic region than just Greenland. Furthermore, it is associated with changes in expression of WARS2 and TBX15 in multiple tissues including the adrenal gland and subcutaneous adipose tissue, and with regional DNA methylation changes in TBX15.
Fernando Racimo, et al., "Archaic adaptive introgression in TBX15/WARS2" (October 27, 2016).
 doi: http://dx.doi.org/10.1101/033928 .

(Note that earlier versions of the article were released quite a few months ago.)

2 comments:

terryt said...

"this suggests non-Melanesians experienced Denisovan introgression in the area where Denisovan remains were found"

I don't believe it has been disproved that Melanesians too first experienced Denisovan introgression in the area where Denisovan remains were found. To me it is quite possible that at least some aspect of the Melanesian ancestry arrived in SE Asia via a northern route. That would have easily carried a partially Denisovan population to SE Asia.

terryt said...

Furthermore I just found this:

https://www.sciencenews.org/article/dna-data-offer-evidence-unknown-extinct-human-relative

I'd actually be very surprised in modern humans had admixed with even just three pre-modern human species.