Gene up-regulation in heart during mammalian hibernation.
A cDNA library prepared from heart of hibernating golden-mantled ground squirrels, Spermophilus lateralis, was differentially screened to clone genes that were up-regulated during hibernation. Two differentially expressed clones were found after three rounds of screening and were confirmed as up-regulated by Northern blotting. Clone Ang6 encoded a polypeptide with 116 amino acids that was identified as the ventricular isoform of myosin light chain 1 (MLC1(v)). Clone Ang19 coded for 274 amino acid residues of the mitochondrially encoded protein subunit 2 of NADH-ubiquinone oxidoreductase (ND2). Both proteins showed high amino acid sequence identity with their human counterparts, 97.5% for MLC1(v) and 66% for ND2. Northern blot hybridization revealed differential expression of these genes in multiple organs during hibernation. Transcript levels of both were approximately twofold higher in heart and three- to fourfold higher in skeletal muscle of hibernating, versus euthermic, animals. ND2 was also up-regulated in hibernator liver. Hibernation-induced up-regulation of MLC1(v) suggests that a restructuring of myosin subunit composition could contribute to changes in muscle contractility needed for hypothermic function, whereas changes in ND subunit composition may affect the function of the electron transport chain during hibernation.
Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada.
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Fahlman
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Storey
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Storey
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D004579:Electron Transport; D042967:Electron Transport Complex I; D006321:Heart / Q000502:physiology; D006605:Hibernation / Q000235:genetics* / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism*; D018994:Myosin Light Chains / Q000235:genetics; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012589:Sciuridae; D014018:Tissue Distribution; D015854:Up-Regulation
D018076:DNA, Complementary; D018994:Myosin Light Chains; D012333:RNA, Messenger; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I