Genetic variation in taste receptor pseudogenes provides evidence for a dynamic role in human evolution

BMC Evolutionary Biology

Dennis Drayna⁴  Donata Luiselli¹  Gabriella Morini²  Sergio Tofanelli³  Davide Risso¹ 

[1] Department of BiGeA, Laboratory of Molecular Anthropology and Centre for Genome Biology, University of Bologna, via Selmi 3, Bologna, 40126, Italy;University of Gastronomic Sciences, Piazza Vittorio Emanuele 9, Bra, Pollenzo 12042, CN, Italy;Department of Biology, University of Pisa, Via Ghini 13, Pisa, 56126, Italy;National Institute on Deafness and Other Communication Disorders, NIH, Bethesda 20892, MD, USA

关键词: TAS2Rs;    Pseudogenization;    Genetic polymorphisms;    Evolution;    Bitter taste;   

Others  :  1117955
DOI  :  10.1186/s12862-014-0198-8

 received in 2014-05-20, accepted in 2014-09-01,  发布年份 2014

【 摘 要 】

Background

Human bitter taste receptors are encoded by a gene family consisting of 25 functional TAS2R loci. In addition, humans carry 11 TAS2R pseudogenes, some of which display evidence for substantial diversification among species, showing lineage-specific loss of function. Since bitter taste is thought to help prevent the intake of toxic substances, diversity at TAS2R genes could reflect the action of natural selection on the ability to recognize some bitter compounds rather than others. Whether species-specific variation in TAS2R pseudogenes is solely the result of genetic drift or whether it may have been influenced by selection due to different feeding behaviors has been an open question.

Results

In this study, we analyzed patterns of variation at human TAS2R pseudogenes in both African and non-African populations, and compared them to those observable in nonhuman primates and archaic human species. Our results showed a similar worldwide distribution of allelic variation for most of the pseudogenes, with the exception of the TAS2R6P and TAS2R18P loci, both of which presented an unexpected higher frequency of derived alleles outside Africa. At the TAS2R6P locus, two SNPs were found in strong linkage disequilibrium (r² > 0.9) with variants in the functional TAS2R5 gene, which showed signatures of selection. The human TAS2R18P carried a species-specific stop-codon upstream of four polymorphic insertions in the reading frame. SNPs at this locus showed significant positive values in a number of neutrality statistics, and age estimates indicated that they arose after the homo-chimp divergence.

Conclusions

The similar distribution of variation of many human bitter receptor pseudogenes among human populations suggests that they arose from the ancestral forms by a unidirectional loss of function. However we explain the higher frequency of TAS2R6P derived alleles outside Africa as the effect of the balancing selection acting on the closely linked TAS2R5 gene. In contrast, TAS2R18P displayed a more complex history, suggesting an acquired function followed by a recent pseudogenization that predated the divergence of human modern and archaic species, which we hypothesize was associated with adaptions to dietary changes.

【 授权许可】

   
2014 Risso et al.; licensee BioMed Central Ltd.

【 图 表 】

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