Leiomodin-3 dysfunction results in thin filament disorganization and nemaline myopathy.

Nemaline myopathy (NM) is a genetic muscle disorder characterized by muscle dysfunction and electron-dense protein accumulations (nemaline bodies) in myofibers. Pathogenic mutations have been described in 9 genes to date, but the genetic basis remains unknown in many cases. Here, using an approach that combined whole-exome sequencing (WES) and Sanger sequencing, we identified homozygous or compound heterozygous variants in LMOD3 in 21 patients from 14 families with severe, usually lethal, NM. LMOD3 encodes leiomodin-3 (LMOD3), a 65-kDa protein expressed in skeletal and cardiac muscle. LMOD3 was expressed from early stages of muscle differentiation; localized to actin thin filaments, with enrichment near the pointed ends; and had strong actin filament-nucleating activity. Loss of LMOD3 in patient muscle resulted in shortening and disorganization of thin filaments. Knockdown of lmod3 in zebrafish replicated NM-associated functional and pathological phenotypes. Together, these findings indicate that mutations in the gene encoding LMOD3 underlie congenital myopathy and demonstrate that LMOD3 is essential for the organization of sarcomeric thin filaments in skeletal muscle.

[1]  D. MacArthur,et al.  Whole exome sequencing identifies three recessive FIG4 mutations in an apparently dominant pedigree with Charcot–Marie–Tooth disease , 2014, Neuromuscular Disorders.

[2]  E. Olson,et al.  KLHL40 deficiency destabilizes thin filament proteins and promotes nemaline myopathy. , 2014, The Journal of clinical investigation.

[3]  F. Muntoni,et al.  Identification of KLHL41 Mutations Implicates BTB-Kelch-Mediated Ubiquitination as an Alternate Pathway to Myofibrillar Disruption in Nemaline Myopathy. , 2013, American journal of human genetics.

[4]  S. Sandaradura,et al.  Recent advances in nemaline myopathy , 2013, Current opinion in neurology.

[5]  J. Dowling,et al.  Force Measurement During Contraction to Assess Muscle Function in Zebrafish Larvae , 2013, Journal of visualized experiments : JoVE.

[6]  E. Bertini,et al.  Mutations in KLHL40 are a frequent cause of severe autosomal-recessive nemaline myopathy. , 2013, American journal of human genetics.

[7]  C. Ottenheijm,et al.  Troponin activator augments muscle force in nemaline myopathy patients with nebulin mutations , 2013, Journal of Medical Genetics.

[8]  Jun Z. Li,et al.  Dominant mutation of CCDC78 in a unique congenital myopathy with prominent internal nuclei and atypical cores. , 2012, American journal of human genetics.

[9]  D. D’Lima,et al.  Thin-filament length correlates with fiber type in human skeletal muscle. , 2012, American journal of physiology. Cell physiology.

[10]  J. Dowling,et al.  neb: a zebrafish model of nemaline myopathy due to nebulin mutation , 2011, Disease Models & Mechanisms.

[11]  J. Miano,et al.  Leiomodin 1, a New Serum Response Factor-dependent Target Gene Expressed Preferentially in Differentiated Smooth Muscle Cells* , 2011, The Journal of Biological Chemistry.

[12]  T. Svitkina,et al.  Different Localizations and Cellular Behaviors of Leiomodin and Tropomodulin in Mature Cardiomyocyte Sarcomeres , 2010, Molecular biology of the cell.

[13]  A. Kostyukova,et al.  Leiomodin-2 is an antagonist of tropomodulin-1 at the pointed end of the thin filaments in cardiac muscle , 2010, Journal of Cell Science.

[14]  Roberta B. Nowak,et al.  Tropomodulin isoforms regulate thin filament pointed-end capping and skeletal muscle physiology , 2010, The Journal of cell biology.

[15]  J. Dowling,et al.  Zebrafish models of collagen VI-related myopathies , 2010, Human molecular genetics.

[16]  C. Ottenheijm,et al.  Thin filament length dysregulation contributes to muscle weakness in nemaline myopathy patients with nebulin deficiency. , 2009, Human molecular genetics.

[17]  Roberta B. Nowak,et al.  A nebulin ruler does not dictate thin filament lengths. , 2009, Biophysical journal.

[18]  T. Pollard,et al.  Leiomodin Is an Actin Filament Nucleator in Muscle Cells , 2008, Science.

[19]  A. Kostyukova,et al.  Molecular basis of tropomyosin binding to tropomodulin, an actin-capping protein. , 2007, Journal of molecular biology.

[20]  A. Kostyukova Leiomodin/tropomyosin interactions are isoform specific. , 2007, Archives of biochemistry and biophysics.

[21]  E. Kizana,et al.  Dystrophinopathy carrier determination and detection of protein deficiencies in muscular dystrophy using lentiviral MyoD-forced myogenesis , 2007, Neuromuscular Disorders.

[22]  F. Muntoni,et al.  Nemaline myopathy caused by absence of α‐skeletal muscle actin , 2007 .

[23]  Yiming Wu,et al.  Nebulin regulates thin filament length, contractility, and Z‐disk structure in vivo , 2006, The EMBO journal.

[24]  Daniel E. Newburger,et al.  Heterogeneity of nemaline myopathy cases with skeletal muscle α‐actin gene mutations , 2004 .

[25]  A. Kostyukova,et al.  Effect of the Structure of the N Terminus of Tropomyosin on Tropomodulin Function* , 2004, Journal of Biological Chemistry.

[26]  T. Pollard,et al.  Pyrene actin: documentation of the validity of a sensitive assay for actin polymerization , 1983, Journal of Muscle Research & Cell Motility.

[27]  Daniel E. Newburger,et al.  Heterogeneity of nemaline myopathy cases with skeletal muscle alpha-actin gene mutations. , 2004, Annals of neurology.

[28]  K. North,et al.  Single section Western blot , 2003, Neurology.

[29]  T. Palm,et al.  Structure and interactions of the carboxyl terminus of striated muscle alpha-tropomyosin: it is important to be flexible. , 2002, Biophysical journal.

[30]  V. Fowler,et al.  Measurement of thin filament lengths by distributed deconvolution analysis of fluorescence images. , 2002, Biophysical journal.

[31]  Rolf Apweiler,et al.  InterProScan - an integration platform for the signature-recognition methods in InterPro , 2001, Bioinform..

[32]  A. Beggs,et al.  Nemaline myopathy: A clinical study of 143 cases , 2001, Annals of neurology.

[33]  V. Fowler,et al.  Leiomodins: larger members of the tropomodulin (Tmod) gene family. , 2001, Genomics.

[34]  M. G. Cusella De Angelis,et al.  High efficiency myogenic conversion of human fibroblasts by adenoviral vector-mediated MyoD gene transfer. An alternative strategy for ex vivo gene therapy of primary myopathies. , 1998, The Journal of clinical investigation.

[35]  G. Montelione,et al.  The structure of the N-terminus of striated muscle alpha-tropomyosin in a chimeric peptide: nuclear magnetic resonance structure and circular dichroism studies. , 1998, Biochemistry.

[36]  N. Laing,et al.  Nemaline myopathy: current concepts. The ENMC International Consortium and Nemaline Myopathy. , 1997, Journal of medical genetics.

[37]  H. T. ter Keurs,et al.  Effect of thin filament length on the force-sarcomere length relation of skeletal muscle. , 1991, The American journal of physiology.

[38]  T. Kouyama,et al.  Fluorimetry study of N-(1-pyrenyl)iodoacetamide-labelled F-actin. Local structural change of actin protomer both on polymerization and on binding of heavy meromyosin. , 2005, European journal of biochemistry.