title: Novel mutations in NEB cause abnormal nebulin expression and markedly impaired muscle force generation in severe nemaline myopathy.
abstract: BACKGROUND
  Nemaline myopathy (NM) is a congenital muscle disease associated with weakness and the presence of nemaline bodies (rods) in muscle fibers. Mutations in seven genes have been associated with NM, but the most commonly mutated gene is nebulin (NEB), which is thought to account for roughly 50% of cases.
  
  
  RESULTS
  We describe two siblings with severe NM, arthrogryposis and neonatal death caused by two novel NEB mutations: a point mutation in intron 13 and a frameshift mutation in exon 81. Levels of detectable nebulin protein were significantly lower than those in normal control muscle biopsies or those from patients with less severe NM due to deletion of NEB exon 55. Mechanical studies of skinned myofibers revealed marked impairment of force development, with an increase in tension cost.
  
  
  CONCLUSIONS
  Our findings demonstrate that the mechanical phenotype of severe NM is the consequence of mutations that severely reduce nebulin protein levels and suggest that the level of nebulin expression may correlate with the severity of disease.
authors.affiliation: Division of Genetics and Program in Genomics, The Manton Center for Orphan Disease Research, Children's Hospital Boston, Harvard Medical School, 300 Longwood Avenue, CLSB 15026, Boston, MA 02115, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Lawlor
authors.forename: Coen A
authors.initials: CA
authors.lastname: Ottenheijm
authors.forename: Vilma-Lotta
authors.initials: VL
authors.lastname: Lehtokari
authors.forename: Kiyomi
authors.initials: K
authors.lastname: Cho
authors.forename: Katarina
authors.initials: K
authors.lastname: Pelin
authors.forename: Carina
authors.initials: C
authors.lastname: Wallgren-Pettersson
authors.forename: Henk
authors.initials: H
authors.lastname: Granzier
authors.forename: Alan H
authors.initials: AH
authors.lastname: Beggs