title: Identification of a novel stretch-responsive skeletal muscle gene (Smpx).
abstract: Skeletal muscle is able to respond to a range of stimuli, including stretch and increased load, by increasing in diameter and length in the absence of myofiber division. This type of cellular growth (hypertrophy) is a highly complex process involving division of muscle precursor cells (myoblasts) and their fusion to existing muscle fibers as well as increased protein synthesis and decreased protein degradation. Underlying the alterations in protein levels are increases in a range of specific mRNAs including those coding for structural proteins and proteins that regulate the hypertrophic process. Seven days of passive stretch in vivo of tibialis anterior (TA) muscle has been shown to elicit muscle hypertrophy. We have identified a cDNA corresponding to an mRNA that exhibits increased expression in response to 7 days of passive stretch imposed on TA muscles in vivo. This 944-bp novel murine transcript is expressed primarily in cardiac and skeletal muscle and to a lesser extent in brain. Translation of the transcript revealed an open reading frame of 85 amino acids encoding a nuclear localization signal and two overlapping casein kinase II phosphorylation sites. This gene has been called "small muscle protein (X chromosome)" (Smpx; HGMW-approved human gene symbol SMPX) and we hypothesize that it plays a role in skeletal muscle hypertrophy.
authors.affiliation: Molecular Pathology, Imperial College of Science, Technology, and Medicine, London, SW7 2AZ, United Kingdom. t.kemp@ic.ac.uk
authors.forename: T J
authors.initials: TJ
authors.lastname: Kemp
authors.forename: T J
authors.initials: TJ
authors.lastname: Sadusky
authors.forename: M
authors.initials: M
authors.lastname: Simon
authors.forename: R
authors.initials: R
authors.lastname: Brown
authors.forename: M
authors.initials: M
authors.lastname: Eastwood
authors.forename: D A
authors.initials: DA
authors.lastname: Sassoon
authors.forename: G R
authors.initials: GR
authors.lastname: Coulton
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics; D002874:Chromosome Mapping; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D004622:Embryo, Mammalian / Q000378:metabolism; D005091:Exons; D005786:Gene Expression Regulation; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D007438:Introns; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D018272:Porins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013047:Specific Pathogen-Free Organisms; D013314:Stress, Mechanical; D014018:Tissue Distribution; D014960:X Chromosome / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D009124:Muscle Proteins; D018272:Porins; D012333:RNA, Messenger; C433890:SMPX protein, human; C499035:Smpx protein, mouse