title: Alternative splicing alterations of Ca2+ handling genes are associated with Ca2+ signal dysregulation in myotonic dystrophy type 1 (DM1) and type 2 (DM2) myotubes.
abstract: OBJECTIVE
  The pathogenesis of myotonic dystrophy type 1 (DM1) and type 2 (DM2) has been related to the aberrant splicing of several genes, including those encoding for ryanodine receptor 1 (RYR1), sarcoplasmatic/endoplasmatic Ca(2+)-ATPase (SERCA) and α1S subunit of voltage-gated Ca(2+) channels (Cav 1.1). The aim of this study is to determine whether alterations of these genes are associated with changes in the regulation of intracellular Ca(2+) homeostasis and signalling.
  
  
  METHODS
  We analysed the expression of RYR1, SERCA and Cav 1.1 and the intracellular Ca(2+) handling in cultured myotubes isolated from DM1, DM2 and control muscle biopsies by semiquantitative RT-PCR and confocal Ca(2+) imaging respectively.
  
  
  RESULTS
  (i) The alternative splicing of RYR1, SERCA and Cav 1.1 was more severely affected in DM1 than in DM2 myotubes; (ii) DM1 myotubes exhibited higher resting intracellular Ca(2+) levels than DM2; (iii) the amplitude of intracellular Ca(2+) transients induced by sustained membrane depolarization was higher in DM1 myotubes than in controls, whereas DM2 showed opposite behaviour; and (iv) in both DM myotubes, Ca(2+) release from sarcoplasmic reticulum through RYR1 was lower than in controls.
  
  
  CONCLUSIONS
  The aberrant splicing of RYR1, SERCA1 and Cav 1.1 may alter intracellular Ca(2+) signalling in DM1 and DM2 myotubes. The differing dysregulation of intracellular Ca(2+) handling in DM1 and DM2 may explain their distinct sarcolemmal hyperexcitabilities.
authors.affiliation: Fondazione Don Carlo Gnocchi, ONLUS, Milan, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Santoro
authors.forename: Roberto
authors.initials: R
authors.lastname: Piacentini
authors.forename: Marcella
authors.initials: M
authors.lastname: Masciullo
authors.forename: Maria Laura Ester
authors.initials: ML
authors.lastname: Bianchi
authors.forename: Anna
authors.initials: A
authors.lastname: Modoni
authors.forename: Maria Vittoria
authors.initials: MV
authors.lastname: Podda
authors.forename: Enzo
authors.initials: E
authors.lastname: Ricci
authors.forename: Gabriella
authors.initials: G
authors.lastname: Silvestri
authors.forename: Claudio
authors.initials: C
authors.lastname: Grassi
mesh_terms: D000328:Adult; D000368:Aged; D017398:Alternative Splicing; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics; D020746:Calcium Channels, L-Type; D020013:Calcium Signaling / Q000235:genetics*; D006706:Homeostasis; D006801:Humans; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D009223:Myotonic Dystrophy / Q000235:genetics*; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000235:genetics
chemical_list: C412223:CACNA1S protein, human; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506943:ATP2A1 protein, human; D002118:Calcium
keywords: Cav1.1; RYR1; SERCA; intracellular calcium signals; myotonic dystrophy; myotubes