title: Independent evolution of bitter-taste sensitivity in humans and chimpanzees.
abstract: It was reported over 65 years ago that chimpanzees, like humans, vary in taste sensitivity to the bitter compound phenylthiocarbamide (PTC). This was suggested to be the result of a shared balanced polymorphism, defining the first, and now classic, example of the effects of balancing selection in great apes. In humans, variable PTC sensitivity is largely controlled by the segregation of two common alleles at the TAS2R38 locus, which encode receptor variants with different ligand affinities. Here we show that PTC taste sensitivity in chimpanzees is also controlled by two common alleles of TAS2R38; however, neither of these alleles is shared with humans. Instead, a mutation of the initiation codon results in the use of an alternative downstream start codon and production of a truncated receptor variant that fails to respond to PTC in vitro. Association testing of PTC sensitivity in a cohort of captive chimpanzees confirmed that chimpanzee TAS2R38 genotype accurately predicts taster status in vivo. Therefore, although Fisher et al.'s observations were accurate, their explanation was wrong. Humans and chimpanzees share variable taste sensitivity to bitter compounds mediated by PTC receptor variants, but the molecular basis of this variation has arisen twice, independently, in the two species.
authors.affiliation: Department of Human Genetics, University of Utah, 15 North 2030 East, Salt Lake City, Utah 84112-5330, USA. swooding@genetics.utah.edu
authors.forename: Stephen
authors.initials: S
authors.lastname: Wooding
authors.forename: Bernd
authors.initials: B
authors.lastname: Bufe
authors.forename: Christina
authors.initials: C
authors.lastname: Grassi
authors.forename: Michael T
authors.initials: MT
authors.lastname: Howard
authors.forename: Anne C
authors.initials: AC
authors.lastname: Stone
authors.forename: Maribel
authors.initials: M
authors.lastname: Vazquez
authors.forename: Diane M
authors.initials: DM
authors.lastname: Dunn
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Meyerhof
authors.forename: Robert B
authors.initials: RB
authors.lastname: Weiss
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bamshad
mesh_terms: D000483:Alleles; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D005838:Genotype; D006071:Gorilla gorilla / Q000235:genetics / Q000502:physiology; D006801:Humans; D002679:Pan troglodytes / Q000235:genetics* / Q000502:physiology*; D010641:Phenotype; D010670:Phenylthiourea / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D013649:Taste / Q000187:drug effects / Q000502:physiology*; D000098706:Taste Receptors, Type 2
chemical_list: D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D000098706:Taste Receptors, Type 2; D010670:Phenylthiourea