@article {451, title = {Congenital Titinopathy: Comprehensive characterization and pathogenic insights.}, journal = {Ann Neurol}, volume = {83}, year = {2018}, month = {2018 Jun}, pages = {1105-1124}, abstract = {

OBJECTIVE: Comprehensive clinical characterization of congenital titinopathy to facilitate diagnosis and management of this important emerging disorder.

METHODS: Using massively parallel sequencing we identified 30 patients from 27 families with 2 pathogenic nonsense, frameshift and/or splice site TTN mutations in trans. We then undertook a detailed analysis of the clinical, histopathological and imaging features of these patients.

RESULTS: All patients had prenatal or early onset hypotonia and/or congenital contractures. None had ophthalmoplegia. Scoliosis and respiratory insufficiency typically developed early and progressed rapidly, whereas limb weakness was often slowly progressive, and usually did not prevent independent walking. Cardiac involvement was present in 46\% of patients. Relatives of 2 patients had dilated cardiomyopathy. Creatine kinase levels were normal to moderately elevated. Increased fiber size variation, internalized nuclei and cores were common histopathological abnormalities. Cap-like regions, whorled or ring fibers, and mitochondrial accumulations were also observed. Muscle magnetic resonance imaging showed gluteal, hamstring and calf muscle involvement. Western blot analysis showed a near-normal sized titin protein in all samples. The presence of 2 mutations predicted to impact both N2BA and N2B cardiac isoforms appeared to be associated with greatest risk of cardiac involvement. One-third of patients had 1 mutation predicted to impact exons present in fetal skeletal muscle, but not included within the mature skeletal muscle isoform transcript. This strongly suggests developmental isoforms are involved in the pathogenesis of this congenital/early onset disorder.

INTERPRETATION: This detailed clinical reference dataset will greatly facilitate diagnostic confirmation and management of patients, and has provided important insights into disease pathogenesis. Ann Neurol 2018;83:1105-1124.

}, issn = {1531-8249}, doi = {10.1002/ana.25241}, author = {Oates, Emily C and Jones, Kristi J and Donkervoort, Sandra and Charlton, Amanda and Brammah, Susan and Smith, John E and Ware, James S and Yau, Kyle S and Swanson, Lindsay C and Whiffin, Nicola and Peduto, Anthony J and Bournazos, Adam and Waddell, Leigh B and Farrar, Michelle A and Sampaio, Hugo A and Teoh, Hooi Ling and Lamont, Phillipa J and Mowat, David and Fitzsimons, Robin B and Corbett, Alastair J and Ryan, Monique M and O{\textquoteright}Grady, Gina L and Sandaradura, Sarah A and Ghaoui, Roula and Joshi, Himanshu and Marshall, Jamie L and Nolan, Melinda A and Kaur, Simranpreet and Punetha, Jaya and Topf, Ana and Harris, Elizabeth and Bakshi, Madhura and Genetti, Casie A and Marttila, Minttu and Werlauff, Ulla and Streichenberger, Nathalie and Pestronk, Alan and Mazanti, Ingrid and Pinner, Jason R and Vuillerot, Carole and Grosmann, Carla and Camacho, Ana and Mohassel, Payam and Leach, Meganne E and Foley, A Reghan and Bharucha-Goebel, Diana and Collins, James and Connolly, Anne M and Gilbreath, Heather R and Iannaccone, Susan T and Castro, Diana and Cummings, Beryl B and Webster, Richard I and Lazaro, Le{\"\i}la and Vissing, John and Coppens, Sandra and Deconinck, Nicolas and Luk, Ho-Ming and Thomas, Neil H and Foulds, Nicola C and Illingworth, Marjorie A and Ellard, Sian and McLean, Catriona A and Phadke, Rahul and Ravenscroft, Gianina and Witting, Nanna and Hackman, Peter and Richard, Isabelle and Cooper, Sandra T and Kamsteeg, Erik-Jan and Hoffman, Eric P and Bushby, Kate and Straub, Volker and Udd, Bjarne and Ferreiro, Ana and North, Kathryn N and Clarke, Nigel F and Lek, Monkol and Beggs, Alan H and B{\"o}nnemann, Carsten G and MacArthur, Daniel G and Granzier, Henk and Davis, Mark R and Laing, Nigel G} } @article {432, title = {Nemaline myopathy and distal arthrogryposis associated with an autosomal recessive~TNNT3~splice variant.}, journal = {Hum Mutat}, volume = {39}, year = {2018}, month = {2018 03}, pages = {383-388}, abstract = {

A male neonate presented with severe weakness, hypotonia, contractures and congenital scoliosis. Skeletal muscle specimens showed marked atrophy and degeneration of fast fibers with striking nemaline rods and hypertrophy of slow fibers that were ultrastructurally normal. A neuromuscular gene panel identified a homozygous essential splice variant in TNNT3 (chr11:1956150G~>~A, NM_006757.3:c.681+1G~>~A). TNNT3 encodes skeletal troponin-T and is associated with autosomal dominant distal arthrogryposis. TNNT3 has not previously been associated with nemaline myopathy (NM), a rare congenital myopathy linked to defects in proteins associated with thin filament structure and regulation. cDNA studies confirmed pathogenic consequences of the splice variant, eliciting exon-skipping and intron retention events leading to a frameshift. Western blot showed deficiency of troponin-T protein with secondary loss of troponin-I . We establish a homozygous splice variant in TNNT3 as the likely cause of severe congenital NM with distal arthrogryposis, characterized by specific involvement of Type-2 fibers and deficiency of troponin-T .

}, keywords = {Arthrogryposis, Genes, Recessive, Humans, Infant, Infant, Newborn, Male, Myopathies, Nemaline, RNA Splice Sites, RNA Splicing, RNA, Messenger, Troponin T}, issn = {1098-1004}, doi = {10.1002/humu.23385}, author = {Sandaradura, Sarah A and Bournazos, Adam and Mallawaarachchi, Amali and Cummings, Beryl B and Waddell, Leigh B and Jones, Kristi J and Troedson, Christopher and Sudarsanam, Annapurna and Nash, Benjamin M and Peters, Gregory B and Algar, Elizabeth M and MacArthur, Daniel G and North, Kathryn N and Brammah, Susan and Charlton, Amanda and Laing, Nigel G and Wilson, Meredith J and Davis, Mark R and Cooper, Sandra T} } @article {364, title = {Improving genetic diagnosis in Mendelian disease with transcriptome sequencing.}, journal = {Sci Transl Med}, volume = {9}, year = {2017}, month = {2017 04 19}, abstract = {

Exome and whole-genome sequencing are becoming increasingly routine approaches in Mendelian disease diagnosis. Despite their success, the current diagnostic rate for genomic analyses across a variety of rare diseases is approximately 25 to 50\%. We explore the utility of transcriptome sequencing [RNA sequencing (RNA-seq)] as a complementary diagnostic tool in a cohort of 50 patients with genetically undiagnosed rare muscle disorders. We describe an integrated approach to analyze patient muscle RNA-seq, leveraging an analysis framework focused on the detection of transcript-level changes that are unique to the patient compared to more than 180 control skeletal muscle samples. We demonstrate the power of RNA-seq to validate candidate splice-disrupting mutations and to identify splice-altering variants in both exonic and deep intronic regions, yielding an overall diagnosis rate of 35\%. We also report the discovery of a highly recurrent de novo intronic mutation in that results in a dominantly acting splice-gain event, disrupting the critical glycine repeat motif of the triple helical domain. We identify this pathogenic variant in a total of 27 genetically unsolved patients in an external collagen VI-like dystrophy cohort, thus explaining approximately 25\% of patients clinically suggestive of having collagen VI dystrophy in whom prior genetic analysis is negative. Overall, this study represents a large systematic application of transcriptome sequencing to rare disease diagnosis and highlights its utility for the detection and interpretation of variants missed by current standard diagnostic approaches.

}, keywords = {Collagen Type VI, High-Throughput Nucleotide Sequencing, Humans, Muscular Diseases, Mutation, Transcriptome}, issn = {1946-6242}, doi = {10.1126/scitranslmed.aal5209}, author = {Cummings, Beryl B and Marshall, Jamie L and Tukiainen, Taru and Lek, Monkol and Donkervoort, Sandra and Foley, A Reghan and Bolduc, Veronique and Waddell, Leigh B and Sandaradura, Sarah A and O{\textquoteright}Grady, Gina L and Estrella, Elicia and Reddy, Hemakumar M and Zhao, Fengmei and Weisburd, Ben and Karczewski, Konrad J and O{\textquoteright}Donnell-Luria, Anne H and Birnbaum, Daniel and Sarkozy, Anna and Hu, Ying and Gonorazky, Hernan and Claeys, Kristl and Joshi, Himanshu and Bournazos, Adam and Oates, Emily C and Ghaoui, Roula and Davis, Mark R and Laing, Nigel G and Topf, Ana and Kang, Peter B and Beggs, Alan H and North, Kathryn N and Straub, Volker and Dowling, James J and Muntoni, Francesco and Clarke, Nigel F and Cooper, Sandra T and B{\"o}nnemann, Carsten G and MacArthur, Daniel G} } @article {534, title = {Variants in SLC18A3, vesicular acetylcholine transporter, cause congenital myasthenic syndrome.}, journal = {Neurology}, volume = {87}, year = {2016}, month = {2016 Oct 04}, pages = {1442-1448}, abstract = {

OBJECTIVE: To describe the clinical and genetic characteristics of presynaptic congenital myasthenic syndrome secondary to biallelic variants in SLC18A3.

METHODS: Individuals from 2 families were identified with biallelic variants in SLC18A3, the gene encoding the vesicular acetylcholine transporter (VAChT), through whole-exome sequencing.

RESULTS: The patients demonstrated features seen in presynaptic congenital myasthenic syndrome, including ptosis, ophthalmoplegia, fatigable weakness, apneic crises, and deterioration of symptoms in cold water for patient 1. Both patients demonstrated moderate clinical improvement on pyridostigmine. Patient 1 had a broader phenotype, including learning difficulties and left ventricular dysfunction. Electrophysiologic studies were typical for a presynaptic defect. Both patients showed profound electrodecrement on low-frequency repetitive stimulation followed by a prolonged period of postactivation exhaustion. In patient 1, this was unmasked only after isometric contraction, a recognized feature of presynaptic disease, emphasizing the importance of activation procedures.

CONCLUSIONS: VAChT is responsible for uptake of acetylcholine into presynaptic vesicles. The clinical and electrographic characteristics of the patients described are consistent with previously reported mouse models of VAChT deficiency. These findings make it very likely that defects in VAChT due to variants in SLC18A3 are a cause of congenital myasthenic syndrome in humans.

}, keywords = {Adolescent, Child, Diagnosis, Differential, Female, Genetic Variation, Humans, Male, Myasthenic Syndromes, Congenital, Vesicular Acetylcholine Transport Proteins}, issn = {1526-632X}, doi = {10.1212/WNL.0000000000003179}, author = {O{\textquoteright}Grady, Gina L and Verschuuren, Corien and Yuen, Michaela and Webster, Richard and Menezes, Manoj and Fock, Johanna M and Pride, Natalie and Best, Heather A and Benavides Damm, Tatiana and Turner, Christian and Lek, Monkol and Engel, Andrew G and North, Kathryn N and Clarke, Nigel F and MacArthur, Daniel G and Kamsteeg, Erik-Jan and Cooper, Sandra T} } @article {455, title = {Variants in the Oxidoreductase PYROXD1 Cause Early-Onset Myopathy with Internalized Nuclei and Myofibrillar Disorganization.}, journal = {Am J Hum Genet}, volume = {99}, year = {2016}, month = {2016 Nov 03}, pages = {1086-1105}, abstract = {

This study establishes PYROXD1 variants as a cause of early-onset myopathy and uses biospecimens and cell lines, yeast, and zebrafish models to elucidate the fundamental role of PYROXD1 in skeletal muscle. Exome sequencing identified recessive variants in PYROXD1 in nine probands from five families. Affected individuals presented in infancy or childhood with slowly progressive proximal and distal weakness, facial weakness, nasal speech, swallowing difficulties, and normal to moderately elevated creatine kinase. Distinctive histopathology showed abundant internalized nuclei, myofibrillar disorganization, desmin-positive inclusions, and thickened Z-bands. PYROXD1 is a nuclear-cytoplasmic pyridine nucleotide-disulphide reductase (PNDR). PNDRs are flavoproteins (FAD-binding) and catalyze pyridine-nucleotide-dependent (NAD/NADH) reduction of thiol residues in other proteins. Complementation experiments in yeast lacking glutathione reductase glr1 show that human PYROXD1 has reductase activity that is strongly impaired by the disease-associated missense mutations. Immunolocalization studies in human muscle and zebrafish myofibers demonstrate that PYROXD1 localizes to the nucleus and to striated sarcomeric compartments. Zebrafish with ryroxD1 knock-down recapitulate features of PYROXD1 myopathy with sarcomeric disorganization, myofibrillar aggregates, and marked swimming defect. We characterize variants in the oxidoreductase PYROXD1 as a cause of early-onset myopathy with distinctive histopathology and introduce altered redox regulation as a primary cause of congenital muscle disease.

}, keywords = {Amino Acid Sequence, Animals, Cell Nucleus, Cercopithecus aethiops, Cohort Studies, COS Cells, Creatine Kinase, Cytoplasm, Distal Myopathies, ELAV-Like Protein 4, Female, Flavoproteins, Gene Deletion, Genetic Variation, Genome-Wide Association Study, Glutathione Reductase, HEK293 Cells, Humans, Male, Muscle, Skeletal, Mutation, Missense, Myopathies, Structural, Congenital, Oxidoreductases, Pedigree, Protein Conformation, Saccharomyces cerevisiae Proteins, Zebrafish}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2016.09.005}, author = {O{\textquoteright}Grady, Gina L and Best, Heather A and Sztal, Tamar E and Schartner, Vanessa and Sanjuan-Vazquez, Myriam and Donkervoort, Sandra and Abath Neto, Osorio and Sutton, Roger Bryan and Ilkovski, Biljana and Romero, Norma Beatriz and Stojkovic, Tanya and Dastgir, Jahannaz and Waddell, Leigh B and Boland, Anne and Hu, Ying and Williams, Caitlin and Ruparelia, Avnika A and Maisonobe, Thierry and Peduto, Anthony J and Reddel, Stephen W and Lek, Monkol and Tukiainen, Taru and Cummings, Beryl B and Joshi, Himanshu and Nectoux, Juliette and Brammah, Susan and Deleuze, Jean-Fran{\c c}ois and Ing, Viola Oorschot and Ramm, Georg and Ardicli, Didem and Nowak, Kristen J and Talim, Beril and Topaloglu, Haluk and Laing, Nigel G and North, Kathryn N and MacArthur, Daniel G and Friant, Sylvie and Clarke, Nigel F and Bryson-Richardson, Robert J and B{\"o}nnemann, Carsten G and Laporte, Jocelyn and Cooper, Sandra T} }