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Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar

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...

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Autores principales: Li, Xia, Li, Weihua, Wang, Hong, Cao, Jie, Maehashi, Kenji, Huang, Liquan, Bachmanov, Alexander A, Reed, Danielle R, Legrand-Defretin, Véronique, Beauchamp, Gary K, Brand, Joseph G
Formato: Texto
Lenguaje:English
Publicado: Public Library of Science 2005
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1183522/
https://www.ncbi.nlm.nih.gov/pubmed/16103917
http://dx.doi.org/10.1371/journal.pgen.0010003
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author Li, Xia
Li, Weihua
Wang, Hong
Cao, Jie
Maehashi, Kenji
Huang, Liquan
Bachmanov, Alexander A
Reed, Danielle R
Legrand-Defretin, Véronique
Beauchamp, Gary K
Brand, Joseph G
author_facet Li, Xia
Li, Weihua
Wang, Hong
Cao, Jie
Maehashi, Kenji
Huang, Liquan
Bachmanov, Alexander A
Reed, Danielle R
Legrand-Defretin, Véronique
Beauchamp, Gary K
Brand, Joseph G
author_sort Li, Xia
collection PubMed
description 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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spelling pubmed-11835222005-08-15 Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar Li, Xia Li, Weihua Wang, Hong Cao, Jie Maehashi, Kenji Huang, Liquan Bachmanov, Alexander A Reed, Danielle R Legrand-Defretin, Véronique Beauchamp, Gary K Brand, Joseph G PLoS Genet Research Article 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. Public Library of Science 2005-07 2005-07-25 /pmc/articles/PMC1183522/ /pubmed/16103917 http://dx.doi.org/10.1371/journal.pgen.0010003 Text en Copyright: © 2005 Li et al. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Li, Xia
Li, Weihua
Wang, Hong
Cao, Jie
Maehashi, Kenji
Huang, Liquan
Bachmanov, Alexander A
Reed, Danielle R
Legrand-Defretin, Véronique
Beauchamp, Gary K
Brand, Joseph G
Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar
title Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar
title_full Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar
title_fullStr Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar
title_full_unstemmed Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar
title_short Pseudogenization of a Sweet-Receptor Gene Accounts for Cats' Indifference toward Sugar
title_sort pseudogenization of a sweet-receptor gene accounts for cats' indifference toward sugar
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1183522/
https://www.ncbi.nlm.nih.gov/pubmed/16103917
http://dx.doi.org/10.1371/journal.pgen.0010003
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