title: Troponin activator augments muscle force in nemaline myopathy patients with nebulin mutations.
abstract: BACKGROUND
  Nemaline myopathy-the most common non-dystrophic congenital myopathy-is caused by mutations in thin filament genes, of which the nebulin gene is the most frequently affected one. The nebulin gene codes for the giant sarcomeric protein nebulin, which plays a crucial role in skeletal muscle contractile performance. Muscle weakness is a hallmark feature of nemaline myopathy patients with nebulin mutations, and is caused by changes in contractile protein function, including a lower calcium-sensitivity of force generation. To date no therapy exists to treat muscle weakness in nemaline myopathy. Here, we studied the ability of the novel fast skeletal muscle troponin activator, CK-2066260, to augment force generation at submaximal calcium levels in muscle cells from nemaline myopathy patients with nebulin mutations.
  
  
  METHODS
  Contractile protein function was determined in permeabilised muscle cells isolated from frozen patient biopsies. The effect of 5 μM CK-2066260 on force production was assessed.
  
  
  RESULTS
  Nebulin protein concentrations were severely reduced in muscle cells from these patients compared to controls, while myofibrillar ultrastructure was largely preserved. Both maximal active tension and the calcium-sensitivity of force generation were lower in patients compared to controls. Importantly, CK-2066260 greatly increased the calcium-sensitivity of force generation-without affecting the cooperativity of activation-in patients to levels that exceed those observed in untreated control muscle.
  
  
  CONCLUSIONS
  Fast skeletal troponin activation is a therapeutic mechanism to augment contractile protein function in nemaline myopathy patients with nebulin mutations and with other neuromuscular diseases.
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Josine Marieke
authors.initials: JM
authors.lastname: de Winter
authors.forename: Danielle
authors.initials: D
authors.lastname: Buck
authors.forename: Carlos
authors.initials: C
authors.lastname: Hidalgo
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Jasper
authors.forename: Fady I
authors.initials: FI
authors.lastname: Malik
authors.forename: Nigel F
authors.initials: NF
authors.lastname: Clarke
authors.forename: Ger J M
authors.initials: GJ
authors.lastname: Stienen
authors.forename: Michael W
authors.initials: MW
authors.lastname: Lawlor
authors.forename: Alan H
authors.initials: AH
authors.lastname: Beggs
authors.forename: Coen A C
authors.initials: CA
authors.lastname: Ottenheijm
authors.forename: Henk
authors.initials: H
authors.lastname: Granzier
mesh_terms: D000328:Adult; D001706:Biopsy; D002118:Calcium / Q000378:metabolism; D002675:Child, Preschool; D006801:Humans; D007093:Imidazoles / Q000008:administration & dosage / Q000494:pharmacology*; D007223:Infant; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000473:pathology; D009124:Muscle Proteins / Q000235:genetics*; D053580:Muscle Strength / Q000187:drug effects*; D009154:Mutation / Q000235:genetics*; D017696:Myopathies, Nemaline / Q000188:drug therapy / Q000235:genetics / Q000503:physiopathology*; D011719:Pyrazines / Q000008:administration & dosage / Q000494:pharmacology*; D016896:Treatment Outcome; D014336:Troponin / Q000187:drug effects / Q000378:metabolism*; D055815:Young Adult
chemical_list: D007093:Imidazoles; D009124:Muscle Proteins; D011719:Pyrazines; D014336:Troponin; C035620:nebulin; D002118:Calcium
keywords: Muscle disease