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:Harsh environments enforce the expression of behavioural, morphological, physiological, and reproductive rejoinders, including torpor. Here we study the morphological, cellular, and molecular alterations in torpor architype in the colonial urochordate Botrylloides aff. leachii by employing whole organism Transmission electron (TEM) and light microscope observations, RNA sequencing, real-time polymerase chain reaction (qPCR) quantification of selected genes, and immunoloc- alization of WNT, SMAD and SOX2 gene expressions. On the morphological level, torpor starts with gradual regression of all zooids and buds which leaves the colony surviving as condensed vasculature remnants that may be ‘aroused’ to regenerate fully functional colonies upon changes in the environment. Simultaneously, we observed altered distributions of hemolymph cell types. Phagocytes doubled in number, while the number of morula cells declined by half. In addition, two new circulating cell types were observed, multi-nucleated and bacteria-bearing cells. RNA sequencing technology revealed marked differences in gene expression between different organism compartments and states: active zooids and ampullae, and between mid-torpor and naive colonies, or naive and torpid colonies. Gene Ontology term enrichment analyses further showed disparate biological processes. In torpid colonies, we observed overall 233 up regulated genes. These genes included NR4A2, EGR1, MUC5AC, HMCN2 and. Also, 27 transcription factors were upregulated in torpid colonies including ELK1, HDAC3, RBMX, MAZ, STAT1, STAT4 and STAT6. Interestingly, genes involved in developmental processes such as SPIRE1, RHOA, SOX11, WNT5A and SNX18 were also upregulated in torpid colonies. We further validated the dysregulation of 22 genes during torpor by utilizing qPCR. Immunohistochemistry of representative genes from three signaling pathways revealed high expression of these genes in circulated cells along torpor. WNT agonist administration resulted in early arousal from torpor in 80% of the torpid colonies while in active colonies WNT agonist triggered the torpor state. Abovementioned results thus connote unique transcriptome landscapes associated with Botrylloides leachii torpor.

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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Blood transcriptomics mirror regulatory mechanisms during hibernation

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