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Multigenic natural variation underlies Caenorhabditis elegans olfactory preference for the bacterial pathogen Serratia marcescens. G3-GENES GENOMES GENETICS 2014; 4:265-76. [PMID: 24347628 PMCID: PMC3931561 DOI: 10.1534/g3.113.008649] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The nematode Caenorhabditis elegans can use olfaction to
discriminate among different kinds of bacteria, its major food source. We asked how
natural genetic variation contributes to choice behavior, focusing on differences in
olfactory preference behavior between two wild-type C. elegans
strains. The laboratory strain N2
strongly prefers the odor of Serratia marcescens, a soil bacterium
that is pathogenic to C. elegans, to the odor of Escherichia
coli, a commonly used laboratory food source. The divergent Hawaiian
strain CB4856 has a weaker attraction to Serratia than the
N2
strain, and this behavioral difference has a complex genetic basis. At least three
quantitative trait loci (QTLs) from the CB4856 Hawaii strain (HW) with large effect sizes lead to reduced
Serratia preference when introgressed into an N2
genetic background. These loci interact and have epistatic interactions with at least
two antagonistic QTLs from HW that increase Serratia preference. The
complex genetic architecture of this C. elegans trait is reminiscent
of the architecture of mammalian metabolic and behavioral traits.
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Stäubert C, Le Duc D, Schöneberg T. Examining the Dynamic Evolution of G Protein-Coupled Receptors. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2014. [DOI: 10.1007/978-1-62703-779-2_2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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The Genetic Basis of Primate Behavior: Genetics and Genomics in Field-Based Primatology. INT J PRIMATOL 2013; 35:1-10. [PMID: 25013243 DOI: 10.1007/s10764-013-9732-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Campbell MC, Ranciaro A, Zinshteyn D, Rawlings-Goss R, Hirbo J, Thompson S, Woldemeskel D, Froment A, Rucker JB, Omar SA, Bodo JM, Nyambo T, Belay G, Drayna D, Breslin PAS, Tishkoff SA. Origin and differential selection of allelic variation at TAS2R16 associated with salicin bitter taste sensitivity in Africa. Mol Biol Evol 2013; 31:288-302. [PMID: 24177185 DOI: 10.1093/molbev/mst211] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Bitter taste perception influences human nutrition and health, and the genetic variation underlying this trait may play a role in disease susceptibility. To better understand the genetic architecture and patterns of phenotypic variability of bitter taste perception, we sequenced a 996 bp region, encompassing the coding exon of TAS2R16, a bitter taste receptor gene, in 595 individuals from 74 African populations and in 94 non-Africans from 11 populations. We also performed genotype-phenotype association analyses of threshold levels of sensitivity to salicin, a bitter anti-inflammatory compound, in 296 individuals from Central and East Africa. In addition, we characterized TAS2R16 mutants in vitro to investigate the effects of polymorphic loci identified at this locus on receptor function. Here, we report striking signatures of positive selection, including significant Fay and Wu's H statistics predominantly in East Africa, indicating strong local adaptation and greater genetic structure among African populations than expected under neutrality. Furthermore, we observed a "star-like" phylogeny for haplotypes with the derived allele at polymorphic site 516 associated with increased bitter taste perception that is consistent with a model of selection for "high-sensitivity" variation. In contrast, haplotypes carrying the "low-sensitivity" ancestral allele at site 516 showed evidence of strong purifying selection. We also demonstrated, for the first time, the functional effect of nonsynonymous variation at site 516 on salicin phenotypic variance in vivo in diverse Africans and showed that most other nonsynonymous substitutions have weak or no effect on cell surface expression in vitro, suggesting that one main polymorphism at TAS2R16 influences salicin recognition. Additionally, we detected geographic differences in levels of bitter taste perception in Africa not previously reported and infer an East African origin for high salicin sensitivity in human populations.
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Melis M, Atzori E, Cabras S, Zonza A, Calò C, Muroni P, Nieddu M, Padiglia A, Sogos V, Tepper BJ, Tomassini Barbarossa I. The gustin (CA6) gene polymorphism, rs2274333 (A/G), as a mechanistic link between PROP tasting and fungiform taste papilla density and maintenance. PLoS One 2013; 8:e74151. [PMID: 24040192 PMCID: PMC3767652 DOI: 10.1371/journal.pone.0074151] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Accepted: 07/29/2013] [Indexed: 01/29/2023] Open
Abstract
Taste sensitivity to PROP varies greatly among individuals and is associated with polymorphisms in the bitter receptor gene TAS2R38, and with differences in fungiform papilla density on the anterior tongue surface. Recently we showed that the PROP non-taster phenotype is strongly associated with the G variant of polymorphism rs2274333 (A/G) of the gene that controls the salivary trophic factor, gustin. The aims of this study were 1) to investigate the role of gustin gene polymorphism rs2274333 (A/G), in PROP sensitivity and fungiform papilla density and morphology, and 2) to investigate the effect of this gustin gene polymorphism on cell proliferation and metabolic activity. Sixty-four subjects were genotyped for both genes by PCR techniques, their PROP sensitivity was assessed by scaling and threshold methods, and their fungiform papilla density, diameter and morphology were determined. In vitro experiments examined cell proliferation and metabolic activity, following treatment with saliva of individuals with and without the gustin gene mutation, and with isolated protein, in the two iso-forms. Gustin and TAS2R38 genotypes were associated with PROP threshold (p=0.0001 and p=0.0042), but bitterness intensity was mostly determined by TAS2R38 genotypes (p<0.000001). Fungiform papillae densities were associated with both genotypes (p<0.014) (with a stronger effect for gustin; p=0.0006), but papilla morphology was a function of gustin alone (p<0.0012). Treatment of isolated cells with saliva from individuals with the AA form of gustin or direct application of the active iso-form of gustin protein increased cell proliferation and metabolic activity (p<0.0135). These novel findings suggest that the rs2274333 polymorphism of the gustin gene affects PROP sensitivity by acting on fungiform papilla development and maintenance, and could provide the first mechanistic explanation for why PROP super-tasters are more responsive to a broad range of oral stimuli.
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Affiliation(s)
- Melania Melis
- Department of Biomedical Sciences, University of Cagliari, Monserrato, Italy
| | - Elena Atzori
- Department of Life and Environment Sciences, University of Cagliari, Monserrato, Italy
| | - Stefano Cabras
- Department of Biomedical Sciences, University of Cagliari, Monserrato, Italy
| | - Andrea Zonza
- Department of Biomedical Sciences, University of Cagliari, Monserrato, Italy
| | - Carla Calò
- Department of Life and Environment Sciences, University of Cagliari, Monserrato, Italy
| | - Patrizia Muroni
- Department of Biomedical Sciences, University of Cagliari, Monserrato, Italy
| | - Mariella Nieddu
- Department of Biomedical Sciences, University of Cagliari, Monserrato, Italy
| | - Alessandra Padiglia
- Department of Life and Environment Sciences, University of Cagliari, Monserrato, Italy
| | - Valeria Sogos
- Department of Biomedical Sciences, University of Cagliari, Monserrato, Italy
| | - Beverly J. Tepper
- Department of Food Science, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey, United States of America
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Behrens M, Gunn HC, Ramos PCM, Meyerhof W, Wooding SP. Genetic, Functional, and Phenotypic Diversity in TAS2R38-Mediated Bitter Taste Perception. Chem Senses 2013; 38:475-84. [DOI: 10.1093/chemse/bjt016] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Wooding SP, Atanasova S, Gunn HC, Staneva R, Dimova I, Toncheva D. Association of a bitter taste receptor mutation with Balkan Endemic Nephropathy (BEN). BMC MEDICAL GENETICS 2012; 13:96. [PMID: 23050764 PMCID: PMC3495054 DOI: 10.1186/1471-2350-13-96] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 09/28/2012] [Indexed: 11/10/2022]
Abstract
Background Balkan Endemic Nephropathy (BEN) is late-onset kidney disease thought to arise from chronic exposure to aristolochic acid, a phytotoxin that contaminates wheat supplies in rural areas of Eastern Europe. It has recently been demonstrated that humans are capable of perceiving aristolochic acid at concentrations below 40 nM as the result of high-affinity interactions with the TAS2R43 bitter taste receptor. Further, TAS2R43 harbors high-frequency loss-of-function mutations resulting in 50-fold variability in perception. This suggests that genetic variation in TAS2R43 might affect susceptibility to BEN, with individuals carrying functional forms of the receptor being protected by an ability to detect tainted foods. Methods To determine whether genetic variation in TAS2R43 predicts BEN susceptibility, we examined genotype-phenotype associations in a case–control study. A cohort of 88 affected and 99 control subjects from western Bulgaria were genotyped with respect to two key missense variants and a polymorphic whole-gene deletion of TAS2R43 (W35S, H212R, and wt/Δ), which are known to affect taste sensitivity to aristolochic acid. Tests for association between haplotypes and BEN status were then performed. Results Three major TAS2R43 haplotypes observed in previous studies (TAS2R43-W35/H212, -S35/R212 and –Δ) were present at high frequencies (0.17, 0.36, and 0.47 respectively) in our sample, and a significant association between genotype and BEN status was present (P = 0.020; odds ratio 1.18). However, contrary to expectation, BEN was positively associated with TAS2R43-W35/H212, a highly responsive allele previously shown to confer elevated bitter sensitivity to aristolochic acid, which should drive aversion but might also affect absorption, altering toxin activation. Conclusions Our findings are at strong odds with the prediction that carriers of functional alleles of TAS2R43 are protected from BEN by an ability to detect and avoid aristolochic acid exposure. Evidence for a positive association between high-sensitivity alleles and BEN status suggests instead that possession of toxin-responsive receptor variants may paradoxically increase vulnerability, possibly by shifting attractive responses associated with low-intensity bitter sensations. The broad-spectrum tuning of the ~25-member TAS2R family as a whole toward xenobiotics points to a potentially far-reaching relevance of bitter responses to exposure-related disease in both individuals and populations.
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Affiliation(s)
- Stephen P Wooding
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75244, USA.
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Hayakawa T, Sugawara T, Go Y, Udono T, Hirai H, Imai H. Eco-geographical diversification of bitter taste receptor genes (TAS2Rs) among subspecies of chimpanzees (Pan troglodytes). PLoS One 2012; 7:e43277. [PMID: 22916235 PMCID: PMC3420883 DOI: 10.1371/journal.pone.0043277] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2012] [Accepted: 07/18/2012] [Indexed: 12/03/2022] Open
Abstract
Chimpanzees (Pan troglodytes) have region-specific difference in dietary repertoires from East to West across tropical Africa. Such differences may result from different genetic backgrounds in addition to cultural variations. We analyzed the sequences of all bitter taste receptor genes (cTAS2Rs) in a total of 59 chimpanzees, including 4 putative subspecies. We identified genetic variations including single-nucleotide variations (SNVs), insertions and deletions (indels), gene-conversion variations, and copy-number variations (CNVs) in cTAS2Rs. Approximately two-thirds of all cTAS2R haplotypes in the amino acid sequence were unique to each subspecies. We analyzed the evolutionary backgrounds of natural selection behind such diversification. Our previous study concluded that diversification of cTAS2Rs in western chimpanzees (P. t. verus) may have resulted from balancing selection. In contrast, the present study found that purifying selection dominates as the evolutionary form of diversification of the so-called human cluster of cTAS2Rs in eastern chimpanzees (P. t. schweinfurthii) and that the other cTAS2Rs were under no obvious selection as a whole. Such marked diversification of cTAS2Rs with different evolutionary backgrounds among subspecies of chimpanzees probably reflects their subspecies-specific dietary repertoires.
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Affiliation(s)
- Takashi Hayakawa
- Molecular Biology Section, Department of Cellular and Molecular Biology, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
- Japan Society for Promotion of Science, Tokyo, Japan
| | - Tohru Sugawara
- Molecular Biology Section, Department of Cellular and Molecular Biology, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
| | - Yasuhiro Go
- Molecular Biology Section, Department of Cellular and Molecular Biology, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
| | - Toshifumi Udono
- Kumamoto Sanctuary, Wildlife Research Center of Kyoto University, Uki, Kumamoto, Japan
| | - Hirohisa Hirai
- Molecular Biology Section, Department of Cellular and Molecular Biology, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
| | - Hiroo Imai
- Molecular Biology Section, Department of Cellular and Molecular Biology, Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan
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Abstract
The central preoccupation of human genetics is an effort to understand the genotypic basis of human phenotypic diversity. Although recent progress in identifying the genes that, when mutated, underlie major genetic diseases has been rapid, knowledge of the genetic influences on the vast range of variable, and at least partially heritable, traits that constitute the "normal" range of human phenotypic variation lags. Spectacular advances in our knowledge of human genetic variation have laid the groundwork for a synthesis of insights from medical genetics, population genetics, molecular evolution, and the study of human origins that places basic constraints on models of human genetic individuality. Balancing selection, local adaptation, mutation-selection balance, and founder effects have all extensively shaped contemporary genetic variation. Long-term-balancing selection appears largely to reflect the consequences of host-pathogen arms races. Local adaptation has been widespread-and involved responses to a plethora of selective pressures, some identifiable but most unknown. However, it appears to be a combination of mutation-selection balance and founder effects that largely accounts for genetic individuality. If true, this inference has major implications for future research programs in human genetics.
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Affiliation(s)
- Maynard V Olson
- Department of Medicine, Division of Medical Genetics, University of Washington, Seattle, WA 98195, USA.
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Lipchock SV, Reed DR, Mennella JA. Relationship between bitter-taste receptor genotype and solid medication formulation usage among young children: a retrospective analysis. Clin Ther 2012; 34:728-33. [PMID: 22440514 PMCID: PMC3341939 DOI: 10.1016/j.clinthera.2012.02.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 02/07/2012] [Accepted: 02/07/2012] [Indexed: 11/18/2022]
Abstract
BACKGROUND Children often refuse to take medication in liquid formulation because of its unpleasant taste. Recent advances in taste genetics have provided some insight into individual differences in taste among children: due to their genotype, some prefer more intense sweetness and are more sensitive to bitter tastes and thus may have different needs for medication formulation. OBJECTIVE The aims of this study were to: (1) test the a priori hypothesis that children with the bitter-sensitive genotypes are more likely to have experienced solid medication formulations than those with the bitter-insensitive genotype; and (2) conduct post hoc analyses to examine the relationship between genotype and most preferred level of sucrose in water because sweeteners are a common component of liquid formulations. METHODS The following data were obtained from healthy, 3- to 10-year-old children who participated in 1 of 5 taste-research studies: taste genotype for alleles of the bitter-taste receptor TAS2R38; data from retrospective reports of solid medication formulation usage and favorite beverage; and most preferred level of sucrose in water, as determined psychophysically. RESULTS Data from 448 children were included (245 girls, 203 boys; mean age, 7.8 years). Children with ≥1 bitter-sensitive allele (TAS2R38 PP or AP genotype) were more likely to have taken medication in solid formulation than were bitter-insensitive (AA genotype) children. Children with the PP genotype preferred higher concentrations of sucrose in water, and their favorite beverage contained more grams of sugar compared with children with the AA genotype. CONCLUSIONS Taste genotype was associated with experience with solid medication formulations and preference for more intense sweetness. This finding suggests that taste genetics might be an important factor in formulation choice and compliance in the pediatric population.
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