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Rapinski M, Cuerrier A, Davy D. Giving a voice to "the silent killer": a knowledge, attitude and practice study of diabetes among French Guiana's Parikweneh people. JOURNAL OF ETHNOBIOLOGY AND ETHNOMEDICINE 2024; 20:83. [PMID: 39237925 PMCID: PMC11378631 DOI: 10.1186/s13002-024-00713-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2024] [Accepted: 07/22/2024] [Indexed: 09/07/2024]
Abstract
BACKGROUND The prevalence of type 2 diabetes (T2D) in the French overseas department of French Guiana, South America, nearly doubles that in its European counterpart, Metropolitan France. This region is demographically diverse and includes several populations of Indigenous Peoples. Although such populations are at particular risk of developing T2D across the Americas, very little is known about their health status in French Guiana, and accurate numbers of diabetic patients do not exist. METHODS In light of a potential public health crisis, an ethnomedicinal study of diabetes experienced by Indigenous Parikweneh was conducted to provide better insight into the knowledge, attitudes and practices (KAP) related to this quickly emerging disease in French Guiana. Altogether, 75 interviews were conducted with community members and Elders, as well as healthcare professionals and administrators providing services to the Parikweneh population of Macouria and Saint-Georges de l'Oyapock. RESULTS Interviews suggest a high incidence of T2D in this population, with cases that have risen quickly since the mid-twentieth century. Parikweneh participants linked the development of the illness to dietary changes, notably through the introduction of new and sweet foods. Recognizing the complexity of diabetes and its symptoms, diabetic patients highlighted the importance of biomedical treatments and follow-ups, though they frequently alternated or used them concomitantly with Parikweneh medicines. With the help of biomedical tools (i.e. glucometer), local medicinal practices mirrored biomedical approaches through dietary adaptation and the use of medicinal animals and plants for glycaemic control and the treatment of complications from the disease. CONCLUSION Parikweneh are appropriating T2D into their knowledge system and adapting their health system in response to this relatively new health concern. A greater understanding of local practices and perceptions relating to T2D among medical staff may therefore be beneficial for meeting patients' needs, providing greater autonomy in their health path, and improving treatment outcomes.
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Affiliation(s)
- Michael Rapinski
- Institut de Recherche en Biologie Végétale (IRBV), Université de Montréal, Jardin Botanique de Montréal, 4101 Sherbrooke Est, Montréal, QC, H1X 2B2, Canada.
- Laboratoire Écologie, Évolution, Interactions des Systèmes Amazoniens (LEEISA), CNRS, IFREMER, Université de Guyane, 97300, Cayenne, French Guiana, France.
| | - Alain Cuerrier
- Institut de Recherche en Biologie Végétale (IRBV), Université de Montréal, Jardin Botanique de Montréal, 4101 Sherbrooke Est, Montréal, QC, H1X 2B2, Canada
| | - Damien Davy
- Laboratoire Écologie, Évolution, Interactions des Systèmes Amazoniens (LEEISA), CNRS, IFREMER, Université de Guyane, 97300, Cayenne, French Guiana, France
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Wu DD, Irwin DM. Evolution of Trichocyte Keratin Associated Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1054:47-56. [PMID: 29797267 DOI: 10.1007/978-981-10-8195-8_5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The major components of hair are keratins and keratin associated proteins (KRTAPs). KRTAPs form the interfilamentous matrix between intermediate filament bundles through extensive disulfide bond cross-linking with the numerous cysteine residues in hair keratins. A variable number of approximately100-180 genes compose the KRTAP gene family in mammals. KRTAP gene family members present a typical pattern of concerted evolution, and its evolutionary features are consistent with the evolution of mammalian hair. KRATP genes might be more important in determining the structure of cashmere fibers in domestic mammals like sheep and goats. KRTAP gene variants thus should provide information for improved wool by sheep and goat breeding.
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Affiliation(s)
- Dong-Dong Wu
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China.
| | - David M Irwin
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada
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Abstract
Humans have acquired many distinct evolutionary traits after the human-chimpanzee divergence. These phenotypes have resulted from genetic changes that occurred in the human genome and were retained by natural selection. Comparative primate genome analyses reveal that loss-of-function mutations are common in the human genome. Some of these gene inactivation events were revealed to be associated with the emergence of advantageous phenotypes and were therefore positively selected and fixed in modern humans (the "less-ismore" hypothesis). Representative cases of human gene inactivation and their functional implications are presented in this review. Functional studies of additional inactive genes will provide insight into the molecular mechanisms underlying acquisition of various human-specific traits.
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Affiliation(s)
| | | | | | - Yoonsoo Hahn
- Department of Life Science, Research Center for Biomolecules and Biosystems, Chung-Ang University, Seoul 156-756, Korea
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Monteiro Ferreira A, Tomás Marques A, Bhide M, Cubric-Curik V, Hollung K, Knight CH, Raundrup K, Lippolis J, Palmer M, Sales-Baptista E, Araújo SS, de Almeida AM. Sequence Analysis of Bitter Taste Receptor Gene Repertoires in Different Ruminant Species. PLoS One 2015; 10:e0124933. [PMID: 26061084 PMCID: PMC4465170 DOI: 10.1371/journal.pone.0124933] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 03/06/2015] [Indexed: 11/18/2022] Open
Abstract
Bitter taste has been extensively studied in mammalian species and is associated with sensitivity to toxins and with food choices that avoid dangerous substances in the diet. At the molecular level, bitter compounds are sensed by bitter taste receptor proteins (T2R) present at the surface of taste receptor cells in the gustatory papillae. Our work aims at exploring the phylogenetic relationships of T2R gene sequences within different ruminant species. To accomplish this goal, we gathered a collection of ruminant species with different feeding behaviors and for which no genome data is available: American bison, chamois, elk, European bison, fallow deer, goat, moose, mouflon, muskox, red deer, reindeer and white tailed deer. The herbivores chosen for this study belong to different taxonomic families and habitats, and hence, exhibit distinct foraging behaviors and diet preferences. We describe the first partial repertoires of T2R gene sequences for these species obtained by direct sequencing. We then consider the homology and evolutionary history of these receptors within this ruminant group, and whether it relates to feeding type classification, using MEGA software. Our results suggest that phylogenetic proximity of T2R genes corresponds more to the traditional taxonomic groups of the species rather than reflecting a categorization by feeding strategy.
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Affiliation(s)
- Ana Monteiro Ferreira
- Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Universidade de Évora, 7006–554 Évora, Portugal
- Plant Cell Biotechnology Laboratory, Instituto de Tecnologia Química e Biológica António Xavier (ITQB-UNL), Universidade Nova de Lisboa, 2780–157 Oeiras, Portugal
| | | | - Mangesh Bhide
- Laboratory of Biomedical Microbiology and Immunology, University of Veterinary and Pharmacy, 04181 Kosice, Slovakia
| | - Vlatka Cubric-Curik
- University of Zagreb, Faculty of Agriculture, Department of Animal Science, 10000 Zagreb, Croatia
| | - Kristin Hollung
- NOFIMA, Norwegian Food Research Institute, N 1430 Aas, Norway
| | | | | | - John Lippolis
- National Animal Disease Center, Ruminant Diseases and Immunology Research Unit, USDA, Ames, IA, 50010, United States of America
| | - Mitchell Palmer
- National Animal Disease Center, Bacterial Diseases of Livestock Research Unit, USDA, Ames, IA, 50010, United States of America
| | - Elvira Sales-Baptista
- Instituto de Ciências Agrárias e Ambientais Mediterrânicas (ICAAM), Universidade de Évora, 7006–554 Évora, Portugal
- Departamento de Zootecnia, Universidade de Évora, 7002–554 Évora, Portugal
| | - Susana Sousa Araújo
- Plant Cell Biotechnology Laboratory, Instituto de Tecnologia Química e Biológica António Xavier (ITQB-UNL), Universidade Nova de Lisboa, 2780–157 Oeiras, Portugal
- Instituto de Investigação Científica Tropical, 1300–344 Lisboa, Portugal
| | - André Martinho de Almeida
- Plant Cell Biotechnology Laboratory, Instituto de Tecnologia Química e Biológica António Xavier (ITQB-UNL), Universidade Nova de Lisboa, 2780–157 Oeiras, Portugal
- Instituto de Investigação Científica Tropical, 1300–344 Lisboa, Portugal
- CIISA—Centro Interdisciplinar de Investigação em Sanidade Animal, 1300–477 Lisboa, Portugal
- IBET-Instituto de Biologia Experimental e Tecnológica, 2780–157 Oeiras, Portugal
- * E-mail:
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5
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Insights into hominin phenotypic and dietary evolution from ancient DNA sequence data. J Hum Evol 2015; 79:55-63. [DOI: 10.1016/j.jhevol.2014.10.018] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Revised: 09/21/2014] [Accepted: 10/28/2014] [Indexed: 01/02/2023]
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Hayakawa T, Suzuki-Hashido N, Matsui A, Go Y. Frequent Expansions of the Bitter Taste Receptor Gene Repertoire during Evolution of Mammals in the Euarchontoglires Clade. Mol Biol Evol 2014; 31:2018-31. [DOI: 10.1093/molbev/msu144] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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Cygankiewicz AI, Maslowska A, Krajewska WM. Molecular Basis of Taste Sense: Involvement of GPCR Receptors. Crit Rev Food Sci Nutr 2013; 54:771-80. [DOI: 10.1080/10408398.2011.606929] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Li D, Zhang J. Diet shapes the evolution of the vertebrate bitter taste receptor gene repertoire. Mol Biol Evol 2013; 31:303-9. [PMID: 24202612 DOI: 10.1093/molbev/mst219] [Citation(s) in RCA: 125] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Vertebrate Tas2r taste receptors bind to bitter compounds, which are typically poisonous, to elicit bitter sensation to prevent the ingestion of toxins. Previous studies noted a marked variation in the number of Tas2r genes among species, but the underlying cause is unclear. To address this question, we compile the Tas2r gene repertoires from 41 mammals, 4 birds, 2 reptiles, 1 amphibian, and 6 fishes. The number of intact Tas2r genes varies from 0 in the bottlenose dolphin to 51 in the Western clawed frog, with numerous expansions and contractions of the gene family throughout vertebrates, especially among tetrapods. The Tas2r gene number in a species correlates with the fraction of plants in its diet. Because plant tissues contain more toxic compounds than animal tissues do, our observation supports the hypothesis that dietary toxins are a major selective force shaping the diversity of the Tas2r repertoire.
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Affiliation(s)
- Diyan Li
- College of Animal Science and Technology, Sichuan Agricultural University, Ya'an, Sichuan, China
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Ledda M, Kutalik Z, Souza Destito MC, Souza MM, Cirillo CA, Zamboni A, Martin N, Morya E, Sameshima K, Beckmann JS, le Coutre J, Bergmann S, Genick UK. GWAS of human bitter taste perception identifies new loci and reveals additional complexity of bitter taste genetics. Hum Mol Genet 2013; 23:259-67. [PMID: 23966204 PMCID: PMC3857948 DOI: 10.1093/hmg/ddt404] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Human perception of bitterness displays pronounced interindividual variation. This phenotypic variation is mirrored by equally pronounced genetic variation in the family of bitter taste receptor genes. To better understand the effects of common genetic variations on human bitter taste perception, we conducted a genome-wide association study on a discovery panel of 504 subjects and a validation panel of 104 subjects from the general population of São Paulo in Brazil. Correction for general taste-sensitivity allowed us to identify a SNP in the cluster of bitter taste receptors on chr12 (10.88– 11.24 Mb, build 36.1) significantly associated (best SNP: rs2708377, P = 5.31 × 10−13, r2 = 8.9%, β = −0.12, s.e. = 0.016) with the perceived bitterness of caffeine. This association overlaps with—but is statistically distinct from—the previously identified SNP rs10772420 influencing the perception of quinine bitterness that falls in the same bitter taste cluster. We replicated this association to quinine perception (P = 4.97 × 10−37, r2 = 23.2%, β = 0.25, s.e. = 0.020) and additionally found the effect of this genetic locus to be concentration specific with a strong impact on the perception of low, but no impact on the perception of high concentrations of quinine. Our study, thus, furthers our understanding of the complex genetic architecture of bitter taste perception.
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Affiliation(s)
- Mirko Ledda
- Department of Food-Consumer Interaction, Nestlé Research Center, Lausanne, Switzerland
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Newcomb RD, Xia MB, Reed DR. Heritable differences in chemosensory ability among humans. ACTA ACUST UNITED AC 2012. [DOI: 10.1186/2044-7248-1-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Abstract
The combined senses of taste, smell and the common chemical sense merge to form what we call ‘flavor.’ People show marked differences in their ability to detect many flavors, and in this paper, we review the role of genetics underlying these differences in perception. Most of the genes identified to date encode receptors responsible for detecting tastes or odorants. We list these genes and describe their characteristics, beginning with the best-studied case, that of differences in phenylthiocarbamide (PTC) detection, encoded by variants of the bitter taste receptor gene TAS2R38. We then outline examples of genes involved in differences in sweet and umami taste, and discuss what is known about other taste qualities, including sour and salty, fat (termed pinguis), calcium, and the ‘burn’ of peppers. Although the repertoire of receptors involved in taste perception is relatively small, with 25 bitter and only a few sweet and umami receptors, the number of odorant receptors is much larger, with about 400 functional receptors and another 600 potential odorant receptors predicted to be non-functional. Despite this, to date, there are only a few cases of odorant receptor variants that encode differences in the perception of odors: receptors for androstenone (musky), isovaleric acid (cheesy), cis-3-hexen-1-ol (grassy), and the urinary metabolites of asparagus. A genome-wide study also implicates genes other than olfactory receptors for some individual differences in perception. Although there are only a small number of examples reported to date, there may be many more genetic variants in odor and taste genes yet to be discovered.
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Wooding S. Signatures of natural selection in a primate bitter taste receptor. J Mol Evol 2012; 73:257-65. [PMID: 22218679 DOI: 10.1007/s00239-011-9481-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Accepted: 12/14/2011] [Indexed: 01/15/2023]
Abstract
Bitter taste receptors (TAS2Rs) enable animals to detect and avoid toxins in the environment, including noxious defense compounds produced by plants. This suggests that TAS2Rs are under complex pressures from natural selection. To investigate these pressures, we examined signatures of selection in the primate TAS2R38 gene. Whole-gene (1,002 bp) sequences from 40 species representing all major primate taxa uncovered extensive variation. Nucleotide substitutions occurred at 448 positions, resulting in 201 amino acid changes. Two single-nucleotide deletions, one three-nucleotide in-frame deletion, and one premature stop codon were also observed. The rate of non-synonymous substitution (ω = dN/dS), was high in TAS2R38 (ω = 0.60) compared to other genes, but significantly lower than expected under neutrality (P = 4.0 × 10(-9)), indicating that purifying selection has maintained the basic structure of the receptor. However, differences were present among receptor subregions. Non-synonymous rates were significantly lower than expected in transmembrane domains (ω = 0.55, P = 1.18 × 10(-12)) and internal loops (ω = 0.51, P = 7.04 × 10(-5)), but not external loops (ω = 1.16, P = 0.53), and evidence of positive selection was found in external loop 2, which exhibited a high rate (ω = 2.53) consistent with rapid shifts in ligand targeting. These patterns point to a history of rapid yet constrained change in bitter taste responses in the course of primate evolution.
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Affiliation(s)
- Stephen Wooding
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390-8591, USA.
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Sugawara T, Go Y, Udono T, Morimura N, Tomonaga M, Hirai H, Imai H. Diversification of bitter taste receptor gene family in western chimpanzees. Mol Biol Evol 2010; 28:921-31. [PMID: 20961961 DOI: 10.1093/molbev/msq279] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In mammals, bitter taste is mediated by T2R genes, which belong to the large family of seven transmembrane G protein-coupled receptors. Because T2Rs are directly involved in the interaction between mammals and their dietary sources, it is likely that these genes evolved to reflect species' specific diets during mammalian evolution. Here, we investigated the sequences of all 28 putative functional chimpanzee T2R genes (cT2Rs) in 46 western chimpanzees to compare the intraspecies variations in chimpanzees to those already known for all 25 human functional T2R genes (hT2Rs). The numbers of functional genes varied among individuals in western chimpanzees, and most chimpanzees had two or three more functional genes than humans. Similarly to hT2Rs, cT2Rs showed high nucleotide diversity along with a large number of amino acid substitutions. Comparison of the nucleotide substitution patterns in cT2Rs with those in five cT2R pseudogenes and 14 autosomal intergenic noncoding regions among the same individuals revealed that the evolution of cT2R genes was almost identical to that of putative neutral regions with slight but significantly positive Tajima's D values, suggesting that selective constraint on these genes was relaxed with weak balancing selection. These trends have resulted in the occurrence of various divergent alleles of T2Rs within the western chimpanzee populations and in heterozygous individuals who might have the ability to taste a broader range of substances.
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Affiliation(s)
- Tohru Sugawara
- Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan.
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[Molecular cloning and evolutionary analysis of hog badger bitter taste receptor T2R2 gene]. YI CHUAN = HEREDITAS 2009; 31:1113-20. [PMID: 19933092 DOI: 10.3724/sp.j.1005.2009.01113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Recognition of natural bitter toxins through taste is one of the most effective mechanisms of self-safety. An approximate 1 169 bp sequence of the bitter taste receptor T2R2 gene was obtained by PCR and cloning technique from hog badger genomic DNA(GenBank accession number: FJ812727). This sequence contains a complete single exon (without intron) 915 bp in size, which encodes 304 amino acid residues. The isoelectric point (pI) of the protein is 9.76 and its molecular weight is 34.74 kDa. Topology prediction showed that the T2R2 protein contained one N-glycosylation site, one N-myristoylation site, and two potential protein kinase C phosphorylation sites. Additionally, the whole peptide chain was comprised of seven transmembrane helix regions, four extracellular regions, and four intracellular regions. The T2R2 is a hydrophobic protein with a few hydrophilic components. Homology analysis of the T2R2 gene sequences by Clustal W indicated that the cDNA sequence homology of T2R2 gene in hog badger with dog, cat, cattle, horse, chimpanzee, and mouse is 91.4%, 90.6%, 84.4%, 85.4%, 83.8%and 72.1%, respectively, and the homology of amino acid sequence is 85.5%, 85.8%, 74.0%, 77.6%, 75.3% and 61.5%, respectively. The results of nucleotide acid substitution computation and selective test showed that strong purifying selection (functional constraint) occurred between hog badger and the six species, respectively, which mainly existed in the transmembrane regions of T2R2. In addition, the Neighbour-Joining tree of T2R2 gene exons from these seven species is consistent with their species tree, indicating that the T2R2 gene is suitable for constructing molecular phylogenetic tree among different species likewise.
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Dong D, Jones G, Zhang S. Dynamic evolution of bitter taste receptor genes in vertebrates. BMC Evol Biol 2009; 9:12. [PMID: 19144204 PMCID: PMC2646699 DOI: 10.1186/1471-2148-9-12] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Accepted: 01/15/2009] [Indexed: 11/30/2022] Open
Abstract
Background Sensing bitter tastes is crucial for many animals because it can prevent them from ingesting harmful foods. This process is mainly mediated by the bitter taste receptors (T2R), which are largely expressed in the taste buds. Previous studies have identified some T2R gene repertoires, and marked variation in repertoire size has been noted among species. However, the mechanisms underlying the evolution of vertebrate T2R genes remain poorly understood. Results To better understand the evolutionary pattern of these genes, we identified 16 T2R gene repertoires based on the high coverage genome sequences of vertebrates and studied the evolutionary changes in the number of T2R genes during birth-and-death evolution using the reconciled-tree method. We found that the number of T2R genes and the fraction of pseudogenes vary extensively among species. Based on the results of phylogenetic analysis, we showed that T2R gene families in teleost fishes are more diverse than those in tetrapods. In addition to the independent gene expansions in teleost fishes, frogs and mammals, lineage-specific gene duplications were also detected in lizards. Furthermore, extensive gains and losses of T2R genes were detected in each lineage during their evolution, resulting in widely differing T2R gene repertoires. Conclusion These results further support the hypotheses that T2R gene repertoires are closely related to the dietary habits of different species and that birth-and-death evolution is associated with adaptations to dietary changes.
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Affiliation(s)
- Dong Dong
- School of Life Sciences, East China Normal University, Shanghai, PR China.
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Shi P, Zhang J. Extraordinary diversity of chemosensory receptor gene repertoires among vertebrates. Results Probl Cell Differ 2009; 47:1-23. [PMID: 19145414 DOI: 10.1007/400_2008_4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Chemosensation (smell and taste) is important to the survival and reproduction of vertebrates and is mediated by specific bindings of odorants, pheromones, and tastants by chemoreceptors that are encoded by several large gene families. This review summarizes recent comparative genomic and evolutionary studies of vertebrate chemoreceptor genes. It focuses on the remarkable diversity of chemoreceptor gene repertoires in terms of gene number and gene sequence across vertebrates and the evolutionary mechanisms that are responsible for generating this diversity. We argue that the great among-species variation of chemoreceptor gene repertoires is a result of adaptations of individual species to their environments and diets.
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Affiliation(s)
- P Shi
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, The Chinese Academy of Sciences, Arthur-Scheunert-Allee 114-116, 650223, Kunming, China.
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Hao S, Dulake M, Espero E, Sternini C, Raybould HE, Rinaman L. Central Fos expression and conditioned flavor avoidance in rats following intragastric administration of bitter taste receptor ligands. Am J Physiol Regul Integr Comp Physiol 2008; 296:R528-36. [PMID: 19073908 DOI: 10.1152/ajpregu.90423.2008] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
G protein-coupled receptors that signal bitter taste (T2Rs) are expressed in the mucosal lining of the oral cavity and gastrointestinal (GI) tract. In mice, intragastric infusion of T2R ligands activates Fos expression within the caudal viscerosensory portion of the nucleus of the solitary tract (NTS) through a vagal pathway (Hao S, Sternini C, Raybould HE. Am J Physiol Regul Integr Comp Physiol 294: R33-R38, 2008). The present study was performed in rats to further characterize the distribution and chemical phenotypes of brain stem and forebrain neurons activated to express Fos after intragastric gavage of T2R ligands, and to determine a potential behavioral correlate of this central neural activation. Compared with relatively low brain stem and forebrain Fos expression in control rats gavaged intragastrically with water, rats gavaged intragastrically with T2R ligands displayed significantly increased activation of neurons within the caudal medial (visceral) NTS and caudal ventrolateral medulla, including noradrenergic neurons, and within the lateral parabrachial nucleus, central nucleus of the amygdala, and paraventricular nucleus of the hypothalamus. A behavioral correlate of this Fos activation was evidenced when rats avoided consuming flavors that previously were paired with intragastric gavage of T2R ligands. While unconditioned aversive responses to bitter tastants in the oral cavity are often sufficient to inhibit further consumption, a second line of defense may be provided postingestively by ligand-induced signaling at GI T2Rs that signal the brain via vagal sensory inputs to the caudal medulla.
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Affiliation(s)
- Shuzhen Hao
- Vet Med: APC, 1330 Haring Hall, UC Davis, Davis, CA 95616, USA
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Wu DD, Irwin DM, Zhang YP. Molecular evolution of the keratin associated protein gene family in mammals, role in the evolution of mammalian hair. BMC Evol Biol 2008; 8:241. [PMID: 18721477 PMCID: PMC2528016 DOI: 10.1186/1471-2148-8-241] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Accepted: 08/23/2008] [Indexed: 01/14/2023] Open
Abstract
Background Hair is unique to mammals. Keratin associated proteins (KRTAPs), which contain two major groups: high/ultrahigh cysteine and high glycine-tyrosine, are one of the major components of hair and play essential roles in the formation of rigid and resistant hair shafts. Results The KRTAP family was identified as being unique to mammals, and near-complete KRTAP gene repertoires for eight mammalian genomes were characterized in this study. An expanded KRTAP gene repertoire was found in rodents. Surprisingly, humans have a similar number of genes as other primates despite the relative hairlessness of humans. We identified several new subfamilies not previously reported in the high/ultrahigh cysteine KRTAP genes. Genes in many subfamilies of the high/ultrahigh cysteine KRTAP genes have evolved by concerted evolution with frequent gene conversion events, yielding a higher GC base content for these gene sequences. In contrast, the high glycine-tyrosine KRTAP genes have evolved more dynamically, with fewer gene conversion events and thus have a lower GC base content, possibly due to positive selection. Conclusion Most of the subfamilies emerged early in the evolution of mammals, thus we propose that the mammalian ancestor should have a diverse KRTAP gene repertoire. We propose that hair content characteristics have evolved and diverged rapidly among mammals because of rapid divergent evolution of KRTAPs between species. In contrast, subfamilies of KRTAP genes have been homogenized within each species due to concerted evolution.
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Affiliation(s)
- Dong-Dong Wu
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, PR China.
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Hao S, Sternini C, Raybould HE. Role of CCK1 and Y2 receptors in activation of hindbrain neurons induced by intragastric administration of bitter taste receptor ligands. Am J Physiol Regul Integr Comp Physiol 2008; 294:R33-8. [DOI: 10.1152/ajpregu.00675.2007] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
G-protein-coupled receptors signaling bitter taste (T2Rs) in the oral gustatory system and the α-subunit of the taste-specific G-protein gustducin are expressed in the gastrointestinal (GI) tract. α-Subunit of the taste-specific G-protein gustducin colocalizes with markers of enteroendocrine cells in human and mouse GI mucosa, including peptide YY. Activation of T2Rs increases cholecystokinin (CCK) release from the enteroendocrine cell line, STC-1. The aim of this study was to determine whether T2R agonists in the GI tract activate neurons in the nucleus of the solitary tract (NTS) and whether this activation is mediated by CCK and peptide YY acting at CCK1 and Y2 receptors. Immunocytochemistry for the protooncogene c-Fos protein, a marker for neuronal activation, was used to determine activation of neurons in the midregion of the NTS, the region where vagal afferents from the GI tract terminate. Intragastric administration of the T2R agonist denatonium benzoate (DB), or phenylthiocarbamide (PTC), or a combination of T2R agonists significantly increased the number of Fos-positive neurons in the mid-NTS; subdiaphragmatic vagotomy abolished the NTS response to the mixture of T2R agonists. Deletion of CCK1 receptor gene or blockade of CCK1 receptors with devazepide abolishes the activation of NTS neurons in response to DB, but had no effect on the response to PTC. Administration of the Y2 receptor antagonist BIIE0246 blocks the activation of NTS neurons to DB, but not PTC. These findings suggest that activation of neurons in the NTS following administration of T2R agonists to the GI tract involves CCK1 and Y2 receptors located on vagal afferent terminals in the gut wall. T2Rs may regulate GI function via release of regulatory peptides and activation of the vagal reflex pathway.
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Simon SA, de Araujo IE, Gutierrez R, Nicolelis MAL. The neural mechanisms of gustation: a distributed processing code. Nat Rev Neurosci 2007; 7:890-901. [PMID: 17053812 DOI: 10.1038/nrn2006] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Whenever food is placed in the mouth, taste receptors are stimulated. Simultaneously, different types of sensory fibre that monitor several food attributes such as texture, temperature and odour are activated. Here, we evaluate taste and oral somatosensory peripheral transduction mechanisms as well as the multi-sensory integrative functions of the central pathways that support the complex sensations that we usually associate with gustation. On the basis of recent experimental data, we argue that these brain circuits make use of distributed ensemble codes that represent the sensory and post-ingestive properties of tastants.
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Affiliation(s)
- Sidney A Simon
- Department of Neurobiology, Duke University, Durham, North Carolina 27710, USA.
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20
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Li X, Li W, Wang H, Bayley DL, Cao J, Reed DR, Bachmanov AA, Huang L, Legrand-Defretin V, Beauchamp GK, Brand JG. Cats lack a sweet taste receptor. J Nutr 2006; 136:1932S-1934S. [PMID: 16772462 PMCID: PMC2063449 DOI: 10.1093/jn/136.7.1932s] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Xia Li
- Monell Chemical Senses Center, Philadelphia, PA 19104, USA
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21
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Wooding S, Bufe B, Grassi C, Howard MT, Stone AC, Vazquez M, Dunn DM, Meyerhof W, Weiss RB, Bamshad MJ. Independent evolution of bitter-taste sensitivity in humans and chimpanzees. Nature 2006; 440:930-4. [PMID: 16612383 DOI: 10.1038/nature04655] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2005] [Accepted: 02/16/2006] [Indexed: 11/08/2022]
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.
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Affiliation(s)
- Stephen Wooding
- Department of Human Genetics, University of Utah, 15 North 2030 East, Salt Lake City, Utah 84112-5330, USA.
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22
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Affiliation(s)
- Stephen Wooding
- Department of Human Genetics, University of Utah, Salt Lake City, Utah 84112-5330, USA.
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23
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Liang M, Ventura B. Physiological genomics in PG and beyond: July to September 2005. Physiol Genomics 2005. [DOI: 10.1152/physiolgenomics.00212.2005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Shi P, Zhang J. Contrasting Modes of Evolution Between Vertebrate Sweet/Umami Receptor Genes and Bitter Receptor Genes. Mol Biol Evol 2005; 23:292-300. [PMID: 16207936 DOI: 10.1093/molbev/msj028] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Taste reception is fundamental to diet selection in many animals. The genetic basis underlying the evolution and diversity of taste reception, however, is not well understood. Recent discoveries of T1R sweet/umami receptor genes and T2R bitter receptor genes in humans and mice provided an opportunity to address this question. Here, we report the identification of 20 putatively functional T1R genes and 167 T2R genes from the genome sequences of nine vertebrates, including three fishes, one amphibian, one bird, and four mammals. Our comparative genomic analysis shows that orthologous T1R sequences are relatively conserved in evolution and that the T1R gene repertoire remains virtually constant in size across most vertebrates, except for the loss of the T1R2 sweet receptor gene in the sweet-insensitive chicken and the absence of all T1R genes in the tongueless western clawed frog. In contrast, orthologous T2R sequences are more variable, and the T2R repertoire diverges tremendously among species, from only three functional genes in the chicken to 49 in the frog. These evolutionary patterns suggest the relative constancy in the number and type of sweet and umami tastants encountered by various vertebrates or low binding specificities of T1Rs but a large variation in the number and type of bitter compounds detected by different species. Although the rate of gene duplication is much lower in T1Rs than in T2Rs, signals of positive selection are detected during the functional divergences of paralogous T1Rs, as was previously found among paralogous T2Rs. Thus, functional divergence and specialization of taste receptors generally occurred via adaptive evolution.
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Affiliation(s)
- Peng Shi
- Department of Ecology and Evolutionary Biology, University of Michigan, USA
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25
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Soranzo N, Bufe B, Sabeti PC, Wilson JF, Weale ME, Marguerie R, Meyerhof W, Goldstein DB. Positive selection on a high-sensitivity allele of the human bitter-taste receptor TAS2R16. Curr Biol 2005; 15:1257-65. [PMID: 16051168 DOI: 10.1016/j.cub.2005.06.042] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2005] [Revised: 05/31/2005] [Accepted: 06/14/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND During periods of human expansion into new environments, recognition of bitter natural toxins through taste may have conferred an important selective advantage. The G protein-coupled receptor encoded by TAS2R16 mediates response to salicin, amygdalin, and many bitter beta-glucopyranosides. beta-glucopyranosides are ubiquitous in nature, with many having a highly toxic cyanogenic activity. RESULTS We examined evidence for natural selection on the human receptor TAS2R16 by sequencing the entire coding region, as well as part of the 5' and 3' UTRs, in 997 individuals from 60 human populations. We detected signatures of positive selection, indicated by an excess of evolutionarily derived alleles at the nonsynonymous site K172N and two linked sites and significant values of Fay and Wu's H statistics in 19 populations. The estimated age range for the common ancestor of the derived N172 variant is 78,700-791,000 years, placing it in the Middle Pleistocene and before the expansion of early humans out of Africa. Using calcium imaging in cells expressing different receptor variants, we showed that N172 is associated with an increased sensitivity to salicin, arbutin, and five different cyanogenic glycosides. CONCLUSION We have detected a clear signal of positive selection at the bitter-taste receptor gene TAS2R16. We speculate that the increased sensitivity that is shown toward harmful cyanogenic glycosides and conferred by the N172 allele may have driven the signal of selection at an early stage of human evolution.
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Affiliation(s)
- Nicole Soranzo
- Department of Biology, University College London, United Kingdom.
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26
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Abstract
Bitter tastes are among the most salient of life's experiences--who can forget one's first encounter with dandelion milk or a stout beer? Studies of the genes underlying these tastes are providing new perspectives on human origins and health.
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Affiliation(s)
- Stephen Wooding
- Department of Human Genetics, University of Utah, Salt Lake City, 84112-5330, USA.
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27
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Li X, Li W, Wang H, Cao J, Maehashi K, Huang L, Bachmanov AA, Reed DR, Legrand-Defretin V, Beauchamp GK, Brand JG. Pseudogenization of a sweet-receptor gene accounts for cats' indifference toward sugar. PLoS Genet 2005; 1:27-35. [PMID: 16103917 PMCID: PMC1183522 DOI: 10.1371/journal.pgen.0010003] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2005] [Accepted: 03/26/2005] [Indexed: 11/18/2022] Open
Abstract
Although domestic cats (Felis silvestris catus) possess an otherwise functional sense of taste, they, unlike most mammals, do not prefer and may be unable to detect the sweetness of sugars. One possible explanation for this behavior is that cats lack the sensory system to taste sugars and therefore are indifferent to them. Drawing on work in mice, demonstrating that alleles of sweet-receptor genes predict low sugar intake, we examined the possibility that genes involved in the initial transduction of sweet perception might account for the indifference to sweet-tasting foods by cats. We characterized the sweet-receptor genes of domestic cats as well as those of other members of the Felidae family of obligate carnivores, tiger and cheetah. Because the mammalian sweet-taste receptor is formed by the dimerization of two proteins (T1R2 and T1R3; gene symbols Tas1r2 and Tas1r3), we identified and sequenced both genes in the cat by screening a feline genomic BAC library and by performing PCR with degenerate primers on cat genomic DNA. Gene expression was assessed by RT-PCR of taste tissue, in situ hybridization, and immunohistochemistry. The cat Tas1r3 gene shows high sequence similarity with functional Tas1r3 genes of other species. Message from Tas1r3 was detected by RT-PCR of taste tissue. In situ hybridization and immunohistochemical studies demonstrate that Tas1r3 is expressed, as expected, in taste buds. However, the cat Tas1r2 gene shows a 247-base pair microdeletion in exon 3 and stop codons in exons 4 and 6. There was no evidence of detectable mRNA from cat Tas1r2 by RT-PCR or in situ hybridization, and no evidence of protein expression by immunohistochemistry. Tas1r2 in tiger and cheetah and in six healthy adult domestic cats all show the similar deletion and stop codons. We conclude that cat Tas1r3 is an apparently functional and expressed receptor but that cat Tas1r2 is an unexpressed pseudogene. A functional sweet-taste receptor heteromer cannot form, and thus the cat lacks the receptor likely necessary for detection of sweet stimuli. This molecular change was very likely an important event in the evolution of the cat's carnivorous behavior.
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Affiliation(s)
- Xia Li
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
| | - Weihua Li
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
| | - Hong Wang
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
| | - Jie Cao
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
| | - Kenji Maehashi
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
| | - Liquan Huang
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
| | | | - Danielle R Reed
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
| | | | - Gary K Beauchamp
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
- Department of Psychology, School of Arts and Sciences and Department of Anatomy, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
| | - Joseph G Brand
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Veterans Affairs Medical Center, Philadelphia, Pennsylvania, United States of America
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28
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Nelson TM, Munger SD, Boughter JD. Haplotypes at the Tas2r locus on distal chromosome 6 vary with quinine taste sensitivity in inbred mice. BMC Genet 2005; 6:32. [PMID: 15938754 PMCID: PMC1181811 DOI: 10.1186/1471-2156-6-32] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Accepted: 06/06/2005] [Indexed: 11/25/2022] Open
Abstract
Background The detection of bitter-tasting compounds by the gustatory system is thought to alert animals to the presence of potentially toxic food. Some, if not all, bitter stimuli activate specific taste receptors, the T2Rs, which are expressed in subsets of taste receptor cells on the tongue and palate. However, there is evidence for both receptor-dependent and -independent transduction mechanisms for a number of bitter stimuli, including quinine hydrochloride (QHCl) and denatonium benzoate (DB). Results We used brief-access behavioral taste testing of BXD/Ty recombinant inbred (RI) mouse strains to map the major quantitative trait locus (QTL) for taste sensitivity to QHCl. This QTL is restricted to a ~5 Mb interval on chromosome 6 that includes 24 genes encoding T2Rs (Tas2rs). Tas2rs at this locus display in total 307 coding region single nucleotide polymorphisms (SNPs) between the two BXD/Ty RI parental strains, C57BL/6J (quinine-sensitive) and DBA/2J (quinine insensitive); approximately 50% of these mutations are silent. Individual RI lines contain exclusively either C57BL/6J or DBA/2J Tas2r alleles at this locus, and RI lines containing C57BL/6J Tas2r alleles are more sensitive to QHCl than are lines containing DBA/2J alleles. Thus, the entire Tas2r cluster comprises a large haplotype that correlates with quinine taster status. Conclusion These studies, the first using a taste-salient assay to map the major QTL for quinine taste, indicate that a T2R-dependent transduction cascade is responsible for the majority of strain variance in quinine taste sensitivity. Furthermore, the large number of polymorphisms within coding exons of the Tas2r cluster, coupled with evidence that inbred strains exhibit largely similar bitter taste phenotypes, suggest that T2R receptors are quite tolerant to variation.
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Affiliation(s)
- Theodore M Nelson
- Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA
| | - Steven D Munger
- Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA
- Program in Neuroscience, University of Maryland School of Medicine, Baltimore, Maryland, 21201, USA
| | - John D Boughter
- Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, 38163, USA
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29
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Wu SV, Chen MC, Rozengurt E. Genomic organization, expression, and function of bitter taste receptors (T2R) in mouse and rat. Physiol Genomics 2005; 22:139-49. [PMID: 15886333 DOI: 10.1152/physiolgenomics.00030.2005] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mammalian type 2 taste receptors (T2R) are a family of G protein-coupled receptors that mediate bitter signals in taste cells. In the present study, we compared the genomic organization of rodent T2R genes based on the recently completed mouse and rat genomes and examined tissue- and cell-specific expression of T2Rs. Both mouse and rat T2R families consist of 36 intact genes and at least 7 pseudogenes that are mapped to mouse chromosomes 15, 2, and 6 and to rat chromosomes 2, 3, and 4, respectively. All but two T2R genes are clustered on mouse chromosome 6 and rat chromosome 4 with virtually identical genomic organization. The orthologs of the first human T2R gene identified, mT2R119 and rT2R1, are located on mouse chromosome 15 and rat chromosome 2, whereas the novel rodent-specific T2R genes, mT2R134 and rT2R34, are located on mouse chromosome 2 and rat chromosome 3, respectively. Our results, using RT-PCR, demonstrate the presence of transcripts corresponding to the putative denatonium benzoate (DB) and phenylthiocarbamide (PTC) receptors in the antrum, fundus, and duodenum as well as in STC-1 and AR42J cells. The novel rodent-specific T2R gene (mT2R134 and rT2R34) was also expressed in these tissues and cell lines. The addition of DB, PTC, or cycloheximide to AR42J cells induced a rapid increase in the intracellular Ca(2+) concentration. The specificity of these effects is shown by the fact that these bitter stimuli did not induce any detectable Ca(2+) signaling in many other rodent or human cells that do not express receptors or G proteins implicated in bitter taste signaling. These results demonstrate that mouse and rat T2R genes are highly conserved in terms of genomic organization and tissue expression, suggesting that rodent T2Rs are evolved under similar dietary pressure and share bitter sensing functions in the lingual and gastrointestinal systems.
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Affiliation(s)
- S Vincent Wu
- Center for Ulcer Research and Education, Department of Medicine, David Geffen School of Medicine, and Molecular Biology Institute, University of California and Veterans Affairs Greater Los Angeles Healthcare System, 90095, USA
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Go Y, Satta Y, Takenaka O, Takahata N. Lineage-specific loss of function of bitter taste receptor genes in humans and nonhuman primates. Genetics 2005; 170:313-26. [PMID: 15744053 PMCID: PMC1449719 DOI: 10.1534/genetics.104.037523] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Since the process of becoming dead genes or pseudogenes (pseudogenization) is irreversible and can occur rather rapidly under certain environmental circumstances, it is one plausible determinant for characterizing species specificity. To test this evolutionary hypothesis, we analyzed the tempo and mode of duplication and pseudogenization of bitter taste receptor (T2R) genes in humans as well as in 12 nonhuman primates. The results show that primates have accumulated more pseudogenes than mice after their separation from the common ancestor and that lineage-specific pseudogenization becomes more conspicuous in humans than in nonhuman primates. Although positive selection has operated on some amino acids in extracellular domains, functional constraints against T2R genes are more relaxed in primates than in mice and this trend has culminated in the rapid deterioration of the bitter-tasting capability in humans. Since T2R molecules play an important role in avoiding generally bitter toxic and harmful substances, substantial modification of the T2R gene repertoire is likely to reflect different responses to changes in the environment and to result from species-specific food preference during primate evolution.
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Affiliation(s)
- Yasuhiro Go
- Department of Biosystems Science, Graduate University for Advanced Studies (Sokendai), Hayama, Kanagawa, Japan.
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31
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Abstract
A family of approximately 30 TAS2R bitter taste receptors has been identified in mammals. Their genes evolved through adaptive diversification and are linked to chromosomal loci known to influence bitter taste in mice and humans. The agonists for various TAS2Rs have been identified and all of them were established as bitter tastants. TAS2Rs are broadly tuned to detect multiple bitter substances, explaining, in part, how mammals can recognize numerous bitter compounds with a limited set of receptors. The TAS2Rs are expressed in a subset of taste receptor cells, which are distinct from those mediating responses to other taste qualities. However, cells devoted to the detection of sweet, umami, and bitter stimuli share common signal transduction components. Transgenic expression of a human TAS2R in sweet or bitter taste receptor-expressing cells of mice induced either strong attraction or aversion to the receptor's cognate bitter tastant. Thus, dedicated taste receptor cells appear to function as broadly tuned detectors for bitter substances and are wired to elicit aversive behavior.
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Affiliation(s)
- Wolfgang Meyerhof
- German Institute of Human Nutrition Potsdam-Rehbrücke, Department of Molecular Genetics, Arthur-Scheunert-Allee 114-1 16, 14558 Nuthetal, Germany.
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32
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Stewart MK, Clark NL, Merrihew G, Galloway EM, Thomas JH. High genetic diversity in the chemoreceptor superfamily of Caenorhabditis elegans. Genetics 2004; 169:1985-96. [PMID: 15520260 PMCID: PMC1449585 DOI: 10.1534/genetics.104.035329] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We investigated genetic polymorphism in the Caenorhabditis elegans srh and str chemoreceptor gene families, each of which consists of approximately 300 genes encoding seven-pass G-protein-coupled receptors. Almost one-third of the genes in each family are annotated as pseudogenes because of apparent functional defects in N2, the sequenced wild-type strain of C. elegans. More than half of these "pseudogenes" have only one apparent defect, usually a stop codon or deletion. We sequenced the defective region for 31 such genes in 22 wild isolates of C. elegans. For 10 of the 31 genes, we found an apparently functional allele in one or more wild isolates, suggesting that these are not pseudogenes but instead functional genes with a defective allele in N2. We suggest the term "flatliner" to describe genes whose functional vs. pseudogene status is unclear. Investigations of flatliner gene positions, d(N)/d(S) ratios, and phylogenetic trees indicate that they are not readily distinguished from functional genes in N2. We also report striking heterogeneity in the frequency of other polymorphisms among these genes. Finally, the large majority of polymorphism was found in just two strains from geographically isolated islands, Hawaii and Madeira. This suggests that our sampling of wild diversity in C. elegans is narrow and that identification of additional strains from similarly isolated regions will greatly expand the diversity available for study.
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Affiliation(s)
- Mary K Stewart
- Department of Genome Sciences, University of Washington, Seattle, 98195, USA
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