title: Variable phenotype of del45-55 Becker patients correlated with nNOSμ mislocalization and RYR1 hypernitrosylation.
abstract: Duchenne and Becker muscular dystrophies (DMD and BMD) are muscle-wasting diseases caused by mutations in the DMD gene-encoding dystrophin. Usually, out-of-frame deletions give rise to DMD, whereas in-frame deletions result in BMD. BMD patients exhibit a less severe disease because an abnormal but functional dystrophin is produced. This is the rationale for attempts to correct the reading frame by using an exon-skipping strategy. In order to apply this approach to a larger number of patients, a multi-exon skipping strategy of exons 45-55 has been proposed, because it should correct the mRNA reading frame in almost 75% of DMD patients with a deletion. The resulting dystrophin lacks part of the binding site for the neuronal nitric oxide synthase (nNOSμ), which normally binds to spectrin-like repeats 16 and 17 of the dystrophin. Since these domains are encoded by exons 42-45, we investigated the nNOSμ status in muscle biopsies from 12 BMD patients carrying spontaneous deletions spaning exons 45-55. We found a wide spectrum of nNOSμ expression and localization. The strictly cytosolic mislocalization of nNOSμ was associated with the more severe phenotypes. Cytosolic NO production correlated with both hypernitrosylation of the sarcoplasmic reticulum calcium-release-channel ryanodine receptor type-1 (RyR1) and release of calstabin-1, a central hub of Ca(2+) signaling and contraction in muscle. Finally, this study shows that the terminal truncation of the nNOS-binding domain in the 'therapeutic' del45-55 dystrophin is not innocuous, since it can perturb the nNOS-dependent stability of the RyR1/calstabin-1 complex.
authors.affiliation: UM76-UPMC/U974-Inserm/UMR7215-CNRS, Institut de Myologie 105 Bd de l’Hôpital, 75013 Paris, France.
authors.forename: Christel
authors.initials: C
authors.lastname: Gentil
authors.forename: France
authors.initials: F
authors.lastname: Leturcq
authors.forename: Rabah
authors.initials: R
authors.lastname: Ben Yaou
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Kaplan
authors.forename: Pascal
authors.initials: P
authors.lastname: Laforet
authors.forename: Isabelle
authors.initials: I
authors.lastname: Pénisson-Besnier
authors.forename: Caroline
authors.initials: C
authors.lastname: Espil-Taris
authors.forename: Thomas
authors.initials: T
authors.lastname: Voit
authors.forename: Luis
authors.initials: L
authors.lastname: Garcia
authors.forename: France
authors.initials: F
authors.lastname: Piétri-Rouxel
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D016189:Dystrophin / Q000235:genetics; D005091:Exons; D017353:Gene Deletion; D006801:Humans; D008875:Middle Aged; D020388:Muscular Dystrophy, Duchenne / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D052248:Nitric Oxide Synthase Type I / Q000032:analysis* / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D012333:RNA, Messenger / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D022021:Tacrolimus Binding Proteins / Q000378:metabolism
chemical_list: D016189:Dystrophin; C550432:FKBP1A protein, human; D012333:RNA, Messenger; D019837:Ryanodine Receptor Calcium Release Channel; D052248:Nitric Oxide Synthase Type I; D022021:Tacrolimus Binding Proteins