Project description:Mammalian hibernation is a dramatic physiological transition that involves the controlled reduction of regulated body temperature and the consequent depression of all physiological processes. The resulting reduction of metabolism and associated energy expenditure permits survival during extended periods of poor food availability in winter. To date our understanding of the molecular events that give rise to the hibernating phenotype is fragmentary and incomplete. Here, we present a large-scale gene expression screen to explore the transcriptional changes that are associated with the torpid phenotype of the hibernating golden-mantled ground squirrel, Spermophilus lateralis. Expression profiles for liver, cardiac tissue, and brain isolated from summer active, torpid, and interbout aroused animals were generated by hybridization to a squirrel microarray composed of >12,000 cDNA probes. We reveal that the transcriptional changes associated with torpor are modest and generally involve less than 2-fold changes in mRNA level. By profiling the distribution of gene ontological terms in the lists of differentially expressed genes we were able to identify the functional themes that distinguish the summer awake and hibernating phenotypes. In all tissues, the pattern of differential gene expression is consistent with a switch to lipid metabolism during hibernation. In liver, we detected an expression signature suggestive of a profound depression in urea metabolism and detoxification pathways. This expression signature was reproduced in transcript data collected from liver of the13-lined ground squirrel, S. tridecemlineatus, suggesting that this phenotype is conserved between closely related species. The transcriptional changes in cardiac tissue were interpreted as a component of the bradycardia associated with torpor. The function of the differentially expressed transcripts in brain is less transparent, likely due to heterogeneity among the responses of different cell populations in this complex organ.

Project description:Mammalian hibernation is a dramatic physiological transition that involves the controlled reduction of regulated body temperature and the consequent depression of all physiological processes. The resulting reduction of metabolism and associated energy expenditure permits survival during extended periods of poor food availability in winter. To date our understanding of the molecular events that give rise to the hibernating phenotype is fragmentary and incomplete. Here, we present a large-scale gene expression screen to explore the transcriptional changes that are associated with the torpid phenotype of the hibernating golden-mantled ground squirrel, Spermophilus lateralis. Expression profiles for liver, cardiac tissue, and brain isolated from summer active, torpid, and interbout aroused animals were generated by hybridization to a squirrel microarray composed of >12,000 cDNA probes. We reveal that the transcriptional changes associated with torpor are modest and generally involve less than 2-fold changes in mRNA level. By profiling the distribution of gene ontological terms in the lists of differentially expressed genes we were able to identify the functional themes that distinguish the summer awake and hibernating phenotypes. In all tissues, the pattern of differential gene expression is consistent with a switch to lipid metabolism during hibernation. In liver, we detected an expression signature suggestive of a profound depression in urea metabolism and detoxification pathways. This expression signature was reproduced in transcript data collected from liver of the13-lined ground squirrel, S. tridecemlineatus, suggesting that this phenotype is conserved between closely related species. The transcriptional changes in cardiac tissue were interpreted as a component of the bradycardia associated with torpor. The function of the differentially expressed transcripts in brain is less transparent, likely due to heterogeneity among the responses of different cell populations in this complex organ. Keywords: other

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