title: On noxious desmin: functional effects of a novel heterozygous desmin insertion mutation on the extrasarcomeric desmin cytoskeleton and mitochondria.
abstract: Recent studies in desmin (-/-) mice have shown that the targeted ablation of desmin leads to pathological changes of the extrasarcomeric intermediate filament cytoskeleton, as well as structural and functional abnormalities of mitochondria in striated muscle. Here, we report on a novel heterozygous single adenine insertion mutation (c.5141_5143insA) in a 40-year-old patient with a distal myopathy. The insertion mutation leads to a frameshift and a truncated desmin (K239fs242). Using transfection studies in SW13 and BHK21 cells, we show that the K239fsX242 desmin mutant is incapable of forming a desmin intermediate filament network. Furthermore, it induces the collapse of a pre-existing desmin cytoskeleton, alters the subcellular distribution of mitochondria and leads to abnormal cytoplasmic protein aggregates reminiscent of desmin-immunoreactive granulofilamentous material seen in the ultrastructural analysis of the patient's muscle. Analysis of mitochondrial function in isolated saponin-permeablized skeletal muscle fibres from our patient showed decreased maximal rates of respiration with the NAD-dependent substrate combination glutamate and malate, as well as a higher amytal sensitivity of respiration, indicating an in vivo inhibition of complex I activity. Our findings suggest that the heterozygous K239fsX242 desmin insertion mutation has a dominant negative effect on the polymerization process of desmin intermediate filaments and affects not only the subcellular distribution, but also biochemical properties of mitochondria in diseased human skeletal muscle. As a consequence, the intermediate filament pathology-induced mitochondrial dysfunction may contribute to the degeneration/regeneration process leading to progressive muscle dysfunction in human desminopathies.
authors.affiliation: Department of Neurology, University Hospital Bonn, Sigmund-Freud-Str. 25, 53105 Bonn, Germany. rolf.schroeder@ikb.uni-bonn.de
authors.forename: Rolf
authors.initials: R
authors.lastname: Schröder
authors.forename: Bertrand
authors.initials: B
authors.lastname: Goudeau
authors.forename: Monique Casteras
authors.initials: MC
authors.lastname: Simon
authors.forename: Dirk
authors.initials: D
authors.lastname: Fischer
authors.forename: Thomas
authors.initials: T
authors.lastname: Eggermann
authors.forename: Christoph S
authors.initials: CS
authors.lastname: Clemen
authors.forename: Zhenlin
authors.initials: Z
authors.lastname: Li
authors.forename: Jens
authors.initials: J
authors.lastname: Reimann
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Xue
authors.forename: Sabine
authors.initials: S
authors.lastname: Rudnik-Schöneborn
authors.forename: Klaus
authors.initials: K
authors.lastname: Zerres
authors.forename: Peter F M
authors.initials: PF
authors.lastname: van der Ven
authors.forename: Dieter O
authors.initials: DO
authors.lastname: Fürst
authors.forename: Wolfram S
authors.initials: WS
authors.lastname: Kunz
authors.forename: Patrick
authors.initials: P
authors.lastname: Vicart
mesh_terms: D000225:Adenine / Q000737:chemistry; D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004252:DNA Mutational Analysis; D018076:DNA, Complementary / Q000378:metabolism; D003893:Desmin / Q000235:genetics* / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D016368:Frameshift Mutation; D005799:Genes, Dominant; D006579:Heterozygote; D006801:Humans; D008297:Male; D016253:Microscopy, Immunoelectron; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D009135:Muscular Diseases / Q000473:pathology; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009243:NAD / Q000378:metabolism; D016133:Polymerase Chain Reaction; D014162:Transfection
chemical_list: D018076:DNA, Complementary; D003893:Desmin; D009243:NAD; D004247:DNA; D000225:Adenine