- Email: [email protected]
Differential gene expression in thermogenesis and torpor
s 102
Abstracts / Comparative Biochemistry and Physiolog3: Part A 126 (2000) SI-S163
EXERCISE INDUCED CHANGES IN THE EXPRESSION OF MYOGENIC REGULATORY FACTORS IN FAST-TYPE SKELETAL MUSCLE OF THE C O M M O N CARP. Martin C.I. and Johnston I.A. Fish Muscle Research Group, Gatty Marine Laboratory, School of Biology, University of St Andrews, St Andrews, Scotland, KY 16 8LB. During skeletal muscle development in vertebrates, the MyoD family of basic helix-loop-helix (bHLH) myogenic regulatory factors (MRFs - MyoD, Myf-5, myogenin and Myf-6) play a crucial role in muscle determination and differentiation. It has been found that expression of Myf-5 and myogenin proteins is initially down-regulated, then increases to over 150% of control values in response to overload through the ablation of synergists in rat muscles (Sakuma et al., 1999). Forced exercise in fish has been shown to be a powerful stimulus for muscle fibre hypertrophy (Johnston & Moon, 1980). The aim of the present study on common carp was to investigate changes in the expression of MyoD family proteins and the activation of satellite cells in fast-type skeletal nmscle, in response to exercise-induced overload. Johnston, I.A. & Moon, T.M. (1980) J. Exp. Biol. 87:177-194 Sakuma, K. et al. (1999) Biochimica et Biophysica Acta 1428:284-292
DIFFERENTIAL GENE EXPRESSION IN THERMOGENESIS AND T O R P O R
Martin S., Epperson E. and van Breukelen F. Department of Cellular & Structural Biology and Program in Molecular Biology, University of Colorado School of Medicine, Denver, CO USA Hibernation in mammals leads to profound reductions of metabolic, heart and respiratory rates, as well as core body temperatures. These events are highly controlled and spontaneously reversible, yet little is known about the molecular events that give rise to the hibernating phenotype. Hibernators are widely dispersed among mammalian orders, suggesting that this dramatic phenotype arises from a genotype that is common to all mammals. Since phenotype results from the expression of genes, it is likely that substantial progress towards understanding the molecular mechanisms used by hibernators to achieve and survive the extremes of hibernation will be gained from determining the patterns of gene expression that are associated with hibernation. To this end, we have begun to explore the relative changes in expression of both mRNAs and proteins during hibernation. Ultimately, the phenotype of torpor will depend upon the presence, absence or altered activity of proteins. Since changes in levels of proteins are often correlated with changes in the levels of the mRNAs that encode them, methods to look at both are being used. Preliminary results suggest that the data being generated by the mouse and human genome projects will greatly facilitate rapid identification of the differentially regulated gene products during hibernation in ground squirrels at both the mRNA and protein levels. At current levels of resolution, approximately 10% of the proteins expressed in liver appear to be altered during hibernation. It is also of interest to determine whether or not these proteins are actually synthesized during torpor. If synthesis of select gene products occurs at low temperature, unique adaptations of the biosynthetic apparatus relative to other mammals are required. These will be involved not only in function at low temperature, but also to select those gene products that are to be expressed during torpor. Alternatively, it may be that hibernators cease RNA and protein synthesis during torpor and use the euthermia of interbout arousals for biosynthesis of the essential gene products of torpor. Results of in vitro studies indicate that transcriptional elongation ceases at the low body temperatures of torpor and is fully restored during interbout arousal. Likewise, translation, as measured by global polysome distributions and by association of specific mRNAs with polysomes, is inactive during torpor but fully restored during interbout arousal. Understanding of both the qualitative and quantitative changes in gene expression will provide a scaffold for elucidating the mechanisms of mammalian hibernation.
Abstracts / Comparative Biochemistry and Physiolog3: Part A 126 (2000) SI-S163
EXERCISE INDUCED CHANGES IN THE EXPRESSION OF MYOGENIC REGULATORY FACTORS IN FAST-TYPE SKELETAL MUSCLE OF THE C O M M O N CARP. Martin C.I. and Johnston I.A. Fish Muscle Research Group, Gatty Marine Laboratory, School of Biology, University of St Andrews, St Andrews, Scotland, KY 16 8LB. During skeletal muscle development in vertebrates, the MyoD family of basic helix-loop-helix (bHLH) myogenic regulatory factors (MRFs - MyoD, Myf-5, myogenin and Myf-6) play a crucial role in muscle determination and differentiation. It has been found that expression of Myf-5 and myogenin proteins is initially down-regulated, then increases to over 150% of control values in response to overload through the ablation of synergists in rat muscles (Sakuma et al., 1999). Forced exercise in fish has been shown to be a powerful stimulus for muscle fibre hypertrophy (Johnston & Moon, 1980). The aim of the present study on common carp was to investigate changes in the expression of MyoD family proteins and the activation of satellite cells in fast-type skeletal nmscle, in response to exercise-induced overload. Johnston, I.A. & Moon, T.M. (1980) J. Exp. Biol. 87:177-194 Sakuma, K. et al. (1999) Biochimica et Biophysica Acta 1428:284-292
DIFFERENTIAL GENE EXPRESSION IN THERMOGENESIS AND T O R P O R
Martin S., Epperson E. and van Breukelen F. Department of Cellular & Structural Biology and Program in Molecular Biology, University of Colorado School of Medicine, Denver, CO USA Hibernation in mammals leads to profound reductions of metabolic, heart and respiratory rates, as well as core body temperatures. These events are highly controlled and spontaneously reversible, yet little is known about the molecular events that give rise to the hibernating phenotype. Hibernators are widely dispersed among mammalian orders, suggesting that this dramatic phenotype arises from a genotype that is common to all mammals. Since phenotype results from the expression of genes, it is likely that substantial progress towards understanding the molecular mechanisms used by hibernators to achieve and survive the extremes of hibernation will be gained from determining the patterns of gene expression that are associated with hibernation. To this end, we have begun to explore the relative changes in expression of both mRNAs and proteins during hibernation. Ultimately, the phenotype of torpor will depend upon the presence, absence or altered activity of proteins. Since changes in levels of proteins are often correlated with changes in the levels of the mRNAs that encode them, methods to look at both are being used. Preliminary results suggest that the data being generated by the mouse and human genome projects will greatly facilitate rapid identification of the differentially regulated gene products during hibernation in ground squirrels at both the mRNA and protein levels. At current levels of resolution, approximately 10% of the proteins expressed in liver appear to be altered during hibernation. It is also of interest to determine whether or not these proteins are actually synthesized during torpor. If synthesis of select gene products occurs at low temperature, unique adaptations of the biosynthetic apparatus relative to other mammals are required. These will be involved not only in function at low temperature, but also to select those gene products that are to be expressed during torpor. Alternatively, it may be that hibernators cease RNA and protein synthesis during torpor and use the euthermia of interbout arousals for biosynthesis of the essential gene products of torpor. Results of in vitro studies indicate that transcriptional elongation ceases at the low body temperatures of torpor and is fully restored during interbout arousal. Likewise, translation, as measured by global polysome distributions and by association of specific mRNAs with polysomes, is inactive during torpor but fully restored during interbout arousal. Understanding of both the qualitative and quantitative changes in gene expression will provide a scaffold for elucidating the mechanisms of mammalian hibernation.