Gene up-regulation in heart during mammalian hibernation

A cDNA library prepared from heart of hibernating golden-mantled ground squ irrels, Spermophilus lateralis, was differentially screened to clone genes that were up-regulated during hibernation. Two differentially expressed clo nes were found after three rounds of screening and were confirmed as up-reg ulated by Northern blotting. Clone Ang6 encoded a polypeptide with 116 amin o acids that was identified as the ventricular isoform of myosin light chai n 1 (MLC1(v)). Clone Ang19 coded for 274 amino acid residues of the mirocho ndrially encoded protein subunit 2 of NADH- ubiquinone oxidoreductase (ND2) . Both proteins showed high amino acid sequence identity with their human c ounterparts, 97.5% for MLClv, and 66% for ND2. Northern blot hybridization revealed differential expression of these genes in multiple organs during h ibernation. Transcript levels of both were approximately twofold higher in heart and three- to fourfold higher in skeletal muscle of hibernating, vers us euthermic. animals. ND2 was also up-regulated in hibernator liver. Hiber nation-induced up-regulation of MLClv, suggests that a restructuring of myo sin 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 . (C) 2000 Academic Press.