Cellular and Molecular Signals Regulating Plasticity of Skeletal Muscle Fiber Type and Size
Sponsored by the APS Muscle Biology Group

Adult skeletal muscles are composed of individual multi nucleate muscle fibers having a range of physiological and biochemical properties, as well as a range of fiber sizes.   The fiber type and size characteristics of the fibers in a given muscle are not static, but vary in response to the pattern of electrical and mechanical activity that the fibers experience over a period of days or weeks.  This symposium will explore the cellular and molecular signaling systems that underlie the plasticity of adult skeletal muscle fiber type and size.  A general theme will be activity dependent regulation of gene expression and protein levels.  Drs Stefano Schiaffino (University of Padova, Italy) and Martin Schneider (University of Maryland) will consider mechanisms in activity dependent fiber type transformation.  Schiaffino will focus on molecular mechanisms and molecular manipulation of skeletal muscle fiber gene expression in living animals experiencing various patterns of electrical stimulation, whereas Schnieder will present details of the signaling process as studied in isolated adult skeletal muscle fibers maintained and electrically stimulated in culture.  Among others, the transcriptional regulators NFAT, HDAC and MEF2 will be considered.   Drs Karyn Esser (University of Kentucky) and Susan Kandarian (Boston University) will focus on molecular signals underlying the regulation of fiber size.  Esser will focus on signaling pathways leading to fiber hypertrophy, whereas Kandarian will consider mechanisms underlying fiber atrophy.  Signalling pathways considered here will be mTOR, Wnt/b-catenin, NFkB, Bcl3 and any other subsequently identified signals.  A common thread in all talks will be the distinction of those signals influencing fiber type from those influencing fiber size.