title: Identification of 45 novel mutations in the nebulin gene associated with autosomal recessive nemaline myopathy.
abstract: Nemaline myopathy (NM) is a clinically and genetically heterogeneous disorder of skeletal muscle caused by mutations in at least five different genes encoding thin filament proteins of the striated muscle sarcomere. We have previously described 18 different mutations in the last 42 exons of the nebulin gene (NEB) in 18 families with NM. Here we report 45 novel NEB mutations detected by denaturing high-performance liquid chromatography (dHPLC) and sequence analysis of all 183 NEB exons in NM patients from 44 families. Altogether we have identified, including the deletion of exon 55 identified in the Ashkenazi Jewish population, 64 different mutations in NEB segregating with autosomal recessive NM in 55 families. The majority (55%) of the mutations in NEB are frameshift or nonsense mutations predicted to cause premature truncation of nebulin. Point mutations (25%) or deletions (3%) affecting conserved splice signals are predicted in the majority of cases to cause in-frame exon skipping, possibly leading to impaired nebulin-tropomyosin interaction along the thin filament. Patients in 18 families had one of nine missense mutations (14%) affecting conserved amino acids at or in the vicinity of actin or tropomyosin binding sites. In addition, we found the exon 55 deletion in four families. The majority of the patients (in 49/55 families) were shown to be compound heterozygous for two different mutations. The mutations were found in both constitutively and alternatively expressed exons throughout the NEB gene, and there were no obvious mutational hotspots. Patients with more severe clinical pictures tended to have mutations predicted to be more disruptive than patients with milder forms.
authors.affiliation: The Folkhälsan Institute of Genetics and the Department of Medical Genetics, University of Helsinki, Helsinki, Finland. vilma.lehtokari@helsinki.fi
authors.forename: Vilma-Lotta
authors.initials: VL
authors.lastname: Lehtokari
authors.forename: Katarina
authors.initials: K
authors.lastname: Pelin
authors.forename: Maria
authors.initials: M
authors.lastname: Sandbacka
authors.forename: Salla
authors.initials: S
authors.lastname: Ranta
authors.forename: Kati
authors.initials: K
authors.lastname: Donner
authors.forename: Francesco
authors.initials: F
authors.lastname: Muntoni
authors.forename: Caroline
authors.initials: C
authors.lastname: Sewry
authors.forename: Corrado
authors.initials: C
authors.lastname: Angelini
authors.forename: Kate
authors.initials: K
authors.lastname: Bushby
authors.forename: Peter
authors.initials: P
authors.lastname: Van den Bergh
authors.forename: Susan
authors.initials: S
authors.lastname: Iannaccone
authors.forename: Nigel G
authors.initials: NG
authors.lastname: Laing
authors.forename: Carina
authors.initials: C
authors.lastname: Wallgren-Pettersson
mesh_terms: D002851:Chromatography, High Pressure Liquid; D018389:Codon, Nonsense; D004252:DNA Mutational Analysis; D005091:Exons; D005260:Female; D016368:Frameshift Mutation; D017353:Gene Deletion; D005808:Genes, Recessive; D006801:Humans; D007438:Introns; D008297:Male; D009124:Muscle Proteins / Q000235:genetics*; D017696:Myopathies, Nemaline / Q000175:diagnosis / Q000235:genetics*; D017354:Point Mutation; D022821:RNA Splice Sites
chemical_list: D018389:Codon, Nonsense; D009124:Muscle Proteins; D022821:RNA Splice Sites; C035620:nebulin