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Enhanced stability and polyadenylation of select mRNAs support rapid thermogenesis in the brown fat of a hibernator.

Grabek KR, Diniz Behn C, Barsh GS, Hesselberth JR, Martin SL - Elife (2015)

Bottom Line: A cohort of transcripts increased during torpor, paradoxical because transcription effectively ceases at these low temperatures.We show that this increase occurs not by elevated transcription but rather by enhanced stabilization associated with maintenance and/or extension of long poly(A) tails.This subset was enriched in a C-rich motif and genes required for BAT activation, suggesting a model and mechanism to prioritize translation of key proteins for thermogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, United States.

ABSTRACT
During hibernation, animals cycle between torpor and arousal. These cycles involve dramatic but poorly understood mechanisms of dynamic physiological regulation at the level of gene expression. Each cycle, Brown Adipose Tissue (BAT) drives periodic arousal from torpor by generating essential heat. We applied digital transcriptome analysis to precisely timed samples to identify molecular pathways that underlie the intense activity cycles of hibernator BAT. A cohort of transcripts increased during torpor, paradoxical because transcription effectively ceases at these low temperatures. We show that this increase occurs not by elevated transcription but rather by enhanced stabilization associated with maintenance and/or extension of long poly(A) tails. Mathematical modeling further supports a temperature-sensitive mechanism to protect a subset of transcripts from ongoing bulk degradation instead of increased transcription. This subset was enriched in a C-rich motif and genes required for BAT activation, suggesting a model and mechanism to prioritize translation of key proteins for thermogenesis.

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Related in: MedlinePlus

Schematic illustrates library sequencing, read processing, tagannotation, and filtering after the creation of the EDGE-tag transcriptomelibraries (see ‘Materials and methods’).Sequential actions are listed in each box, while the number of resultingreads/EDGE-tags are labeled between boxes. tpm = ‘Tags permillion’.DOI:http://dx.doi.org/10.7554/eLife.04517.005
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fig2s1: Schematic illustrates library sequencing, read processing, tagannotation, and filtering after the creation of the EDGE-tag transcriptomelibraries (see ‘Materials and methods’).Sequential actions are listed in each box, while the number of resultingreads/EDGE-tags are labeled between boxes. tpm = ‘Tags permillion’.DOI:http://dx.doi.org/10.7554/eLife.04517.005

Mentions: A total of 38 EDGE-tag libraries, representing 8 distinct sampling groups (Figure 1B), were sequenced, processed (Figure 2—figure supplement 1), and analyzedfor changes associated with hibernation physiology. For each of the libraries, 90.1± 2.6% of the sequence reads aligned to ground squirrel genomic (Supplementary file3A in Grabek et al., 2014) or mitochondrial DNA(Figure 2A). After normalization, filtering,and annotation (Figure 2B, Figure 2—figure supplement 1), 14,798 EDGE-tagsrepresenting 8,089 unique genes remained (Supplementary file 3B in Grabek et al., 2014). We first clustered the individual samplelibraries by tag abundance using Random Forests (Breiman, 2001). Three main groups were evident (Figure 2C): (1)‘spring’, independent of ambienttemperature, spring cold (SpC), and spring warm (SpW); (2) ‘winter warm’:interbout aroused (IBA), entrance (Ent), and summer active (SA); (3) ‘wintercold’: early torpor (ET), late torpor (LT), and early arousal (EAr). Notably, BATsamples harvested from winter animals at warm body temperature clustered separately fromthose at low body temperature. This separation indicates the transcriptome is dynamicacross a torpor bout.10.7554/eLife.04517.004Figure 2.EDGE-tag library properties.


Enhanced stability and polyadenylation of select mRNAs support rapid thermogenesis in the brown fat of a hibernator.

Grabek KR, Diniz Behn C, Barsh GS, Hesselberth JR, Martin SL - Elife (2015)

Schematic illustrates library sequencing, read processing, tagannotation, and filtering after the creation of the EDGE-tag transcriptomelibraries (see ‘Materials and methods’).Sequential actions are listed in each box, while the number of resultingreads/EDGE-tags are labeled between boxes. tpm = ‘Tags permillion’.DOI:http://dx.doi.org/10.7554/eLife.04517.005
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383249&req=5

fig2s1: Schematic illustrates library sequencing, read processing, tagannotation, and filtering after the creation of the EDGE-tag transcriptomelibraries (see ‘Materials and methods’).Sequential actions are listed in each box, while the number of resultingreads/EDGE-tags are labeled between boxes. tpm = ‘Tags permillion’.DOI:http://dx.doi.org/10.7554/eLife.04517.005
Mentions: A total of 38 EDGE-tag libraries, representing 8 distinct sampling groups (Figure 1B), were sequenced, processed (Figure 2—figure supplement 1), and analyzedfor changes associated with hibernation physiology. For each of the libraries, 90.1± 2.6% of the sequence reads aligned to ground squirrel genomic (Supplementary file3A in Grabek et al., 2014) or mitochondrial DNA(Figure 2A). After normalization, filtering,and annotation (Figure 2B, Figure 2—figure supplement 1), 14,798 EDGE-tagsrepresenting 8,089 unique genes remained (Supplementary file 3B in Grabek et al., 2014). We first clustered the individual samplelibraries by tag abundance using Random Forests (Breiman, 2001). Three main groups were evident (Figure 2C): (1)‘spring’, independent of ambienttemperature, spring cold (SpC), and spring warm (SpW); (2) ‘winter warm’:interbout aroused (IBA), entrance (Ent), and summer active (SA); (3) ‘wintercold’: early torpor (ET), late torpor (LT), and early arousal (EAr). Notably, BATsamples harvested from winter animals at warm body temperature clustered separately fromthose at low body temperature. This separation indicates the transcriptome is dynamicacross a torpor bout.10.7554/eLife.04517.004Figure 2.EDGE-tag library properties.

Bottom Line: A cohort of transcripts increased during torpor, paradoxical because transcription effectively ceases at these low temperatures.We show that this increase occurs not by elevated transcription but rather by enhanced stabilization associated with maintenance and/or extension of long poly(A) tails.This subset was enriched in a C-rich motif and genes required for BAT activation, suggesting a model and mechanism to prioritize translation of key proteins for thermogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, United States.

ABSTRACT
During hibernation, animals cycle between torpor and arousal. These cycles involve dramatic but poorly understood mechanisms of dynamic physiological regulation at the level of gene expression. Each cycle, Brown Adipose Tissue (BAT) drives periodic arousal from torpor by generating essential heat. We applied digital transcriptome analysis to precisely timed samples to identify molecular pathways that underlie the intense activity cycles of hibernator BAT. A cohort of transcripts increased during torpor, paradoxical because transcription effectively ceases at these low temperatures. We show that this increase occurs not by elevated transcription but rather by enhanced stabilization associated with maintenance and/or extension of long poly(A) tails. Mathematical modeling further supports a temperature-sensitive mechanism to protect a subset of transcripts from ongoing bulk degradation instead of increased transcription. This subset was enriched in a C-rich motif and genes required for BAT activation, suggesting a model and mechanism to prioritize translation of key proteins for thermogenesis.

Show MeSH
Related in: MedlinePlus