@article {806, title = {Biallelic loss of function variants in SYT2 cause a treatable congenital onset presynaptic myasthenic syndrome.}, journal = {Am J Med Genet A}, volume = {182}, year = {2020}, month = {2020 10}, pages = {2272-2283}, abstract = {

Synaptotagmins are integral synaptic vesicle membrane proteins that function as calcium sensors and regulate neurotransmitter release at the presynaptic nerve terminal. Synaptotagmin-2 (SYT2), is the major isoform expressed at the neuromuscular junction. Recently, dominant missense variants in SYT2 have been reported as a rare cause of distal motor neuropathy and myasthenic syndrome, manifesting with stable or slowly progressive distal weakness of variable severity along with presynaptic NMJ impairment. These variants are thought to have a dominant-negative effect on synaptic vesicle exocytosis, although the precise pathomechanism remains to be elucidated. Here we report seven patients of five families, with biallelic loss of function variants in SYT2, clinically manifesting with a remarkably consistent phenotype of severe congenital onset hypotonia and weakness, with variable degrees of respiratory involvement. Electrodiagnostic findings were consistent with a presynaptic congenital myasthenic syndrome (CMS) in some. Treatment with an acetylcholinesterase inhibitor pursued in three patients showed clinical improvement with increased strength and function. This series further establishes SYT2 as a CMS-disease gene and expands its clinical and genetic spectrum to include recessive loss-of-function variants, manifesting as a severe congenital onset presynaptic CMS with potential treatment implications.

}, keywords = {Adolescent, Child, Child, Preschool, Female, Genetic Predisposition to Disease, Humans, Male, Muscle Hypotonia, Muscle Weakness, Mutation, Missense, Myasthenic Syndromes, Congenital, Pedigree, Phenotype, Synaptic Transmission, Synaptotagmin II}, issn = {1552-4833}, doi = {10.1002/ajmg.a.61765}, author = {Donkervoort, Sandra and Mohassel, Payam and Laugwitz, Lucia and Zaki, MAH S and Kamsteeg, Erik-Jan and Maroofian, Reza and Chao, Katherine R and Verschuuren-Bemelmans, Corien C and Horber, Veronka and Fock, Annemarie J M and McCarty, Riley M and Jain, Minal S and Biancavilla, Victoria and McMacken, Grace and Nalls, Matthew and Voermans, Nicol C and Elbendary, Hasnaa M and Snyder, Molly and Cai, Chunyu and Lehky, Tanya J and Stanley, Valentina and Iannaccone, Susan T and Foley, A Reghan and Lochm{\"u}ller, Hanns and Gleeson, Joseph and Houlden, Henry and Haack, Tobias B and Horvath, Rita and B{\"o}nnemann, Carsten G} } @article {561, title = {Novel SPEG mutations in congenital myopathies: Genotype-phenotype correlations.}, journal = {Muscle Nerve}, volume = {59}, year = {2019}, month = {2019 03}, pages = {357-362}, abstract = {

INTRODUCTION: Centronuclear myopathies (CNMs) are a subtype of congenital myopathies (CMs) characterized by muscle weakness, predominant type 1 fibers, and increased central nuclei. SPEG (striated preferentially expressed protein kinase) mutations have recently been identified in 7 CM patients (6 with CNMs). We report 2 additional patients with SPEG mutations expanding the phenotype and evaluate genotype-phenotype correlations associated with SPEG mutations.

METHODS: Using whole exome/genome sequencing in CM families, we identified novel recessive SPEG mutations in 2 patients.

RESULTS: Patient 1, with severe muscle weakness requiring respiratory support, dilated cardiomyopathy, ophthalmoplegia, and findings of nonspecific CM on muscle biopsy carried a homozygous SPEG mutation (p.Val3062del). Patient 2, with milder muscle weakness, ophthalmoplegia, and CNM carried compound heterozygous mutations (p.Leu728Argfs*82) and (p.Val2997Glyfs*52).

CONCLUSIONS: The 2 patients add insight into genotype-phenotype correlations of SPEG-associated CMs. Clinicians should consider evaluating a CM patient for SPEG mutations even in the absence of CNM features. Muscle Nerve 59:357-362, 2019.

}, keywords = {Biopsy, Child, Child, Preschool, Consanguinity, Exome, Female, Genetic Association Studies, Humans, Infant, Male, Muscle Proteins, Muscle Weakness, Muscle, Skeletal, Mutation, Myopathies, Structural, Congenital, Protein-Serine-Threonine Kinases, Sequence Analysis}, issn = {1097-4598}, doi = {10.1002/mus.26378}, author = {Qualls, Anita E and Donkervoort, Sandra and Herkert, Johanna C and D{\textquoteright}Gama, Alissa M and Bharucha-Goebel, Diana and Collins, James and Chao, Katherine R and Foley, A Reghan and Schoots, Mirthe H and Jongbloed, Jan D H and B{\"o}nnemann, Carsten G and Agrawal, Pankaj B} } @article {421, title = {Identification of GAA variants through whole exome sequencing targeted to a cohort of 606 patients with unexplained limb-girdle muscle weakness.}, journal = {Orphanet J Rare Dis}, volume = {12}, year = {2017}, month = {2017 11 17}, pages = {173}, abstract = {

BACKGROUND: Late-onset Pompe disease is a rare genetic neuromuscular disorder caused by a primary deficiency of α-glucosidase and the associated accumulation of glycogen in lysosomal vacuoles. The deficiency of α-glucosidase can often be detected using an inexpensive and readily accessible dried blood spot test when Pompe disease is suspected. Like several neuromuscular disorders, Pompe disease typically presents with progressive weakness of limb-girdle muscles and respiratory insufficiency. Due to the phenotypic heterogeneity of these disorders, however, it is often difficult for clinicians to reach a diagnosis for patients with Pompe disease. Six hundred and six patients from a European population were recruited onto our study. Inclusion criteria stipulated that index cases must present with limb-girdle weakness or elevated serum creatine kinase activity. Whole exome sequencing with at least 250~ng DNA was completed using an Illumina exome capture and a 38~Mb baited target. A panel of 169 candidate genes for limb-girdle weakness was analysed for disease-causing variants.

RESULTS: A total of 35 variants within GAA were detected. Ten distinct variants in eight unrelated index cases (and four siblings not sequenced in our study) were considered disease-causing, with the patients presenting with heterogeneous phenotypes. The eight unrelated individuals were compound heterozygotes for two variants. Six patients carried the intronic splice site c.-13~T > G transversion and two of the six patients also carried the exonic p.Glu176ArgfsTer45 frameshift. Four of the ten variants were novel in their association with Pompe disease.

CONCLUSIONS: Here, we highlight the advantage of using whole exome sequencing as a tool for detecting, diagnosing and treating patients with rare, clinically variable genetic disorders.

}, keywords = {Adolescent, Adult, Aged, Aged, 80 and over, alpha-Glucosidases, Child, Child, Preschool, Cohort Studies, Female, Genetic Variation, Glycogen Storage Disease Type II, Humans, Male, Middle Aged, Muscle Weakness, Muscular Dystrophies, Limb-Girdle, Whole Exome Sequencing, Young Adult}, issn = {1750-1172}, doi = {10.1186/s13023-017-0722-1}, author = {Johnson, Katherine and Topf, Ana and Bertoli, Marta and Phillips, Lauren and Claeys, Kristl G and Stojanovic, Vidosava Rakocevic and Peri{\'c}, Stojan and Hahn, Andreas and Maddison, Paul and Akay, Ela and Bastian, Alexandra E and {\L}usakowska, Anna and Kostera-Pruszczyk, Anna and Lek, Monkol and Xu, Liwen and MacArthur, Daniel G and Straub, Volker} } @article {90, title = {Recurrent Muscle Weakness with Rhabdomyolysis, Metabolic Crises, and Cardiac Arrhythmia Due to Bi-allelic TANGO2 Mutations.}, journal = {Am J Hum Genet}, volume = {98}, year = {2016}, month = {2016 Feb 04}, pages = {347-57}, abstract = {

The underlying genetic etiology of rhabdomyolysis remains elusive in a significant fraction of individuals presenting with recurrent metabolic crises and muscle weakness. Using exome sequencing, we identified bi-allelic mutations in TANGO2 encoding transport and Golgi organization 2 homolog (Drosophila) in 12 subjects with episodic rhabdomyolysis, hypoglycemia, hyperammonemia, and susceptibility to life-threatening cardiac tachyarrhythmias. A recurrent homozygous c.460G>A (p.Gly154Arg) mutation was found in four unrelated individuals of Hispanic/Latino origin, and a homozygous \~{}34 kb deletion affecting exons 3-9 was observed in two families of European ancestry. One individual of mixed Hispanic/European descent was found to be compound heterozygous for c.460G>A (p.Gly154Arg) and the deletion of exons 3-9. Additionally, a homozygous exons 4-6 deletion was identified in a consanguineous Middle Eastern Arab family. No homozygotes have been reported for these changes in control databases. Fibroblasts derived from a subject with the recurrent c.460G>A (p.Gly154Arg) mutation showed evidence of increased endoplasmic reticulum stress and a reduction in Golgi volume density in comparison to control. Our results show that the c.460G>A (p.Gly154Arg) mutation and the exons 3-9 heterozygous deletion in TANGO2 are recurrent pathogenic alleles present in the Latino/Hispanic and European populations, respectively, causing considerable morbidity in the homozygotes in these populations.

}, keywords = {Alleles, Arabs, Arrhythmias, Cardiac, Base Sequence, Child, Child, Preschool, Endoplasmic Reticulum Stress, European Continental Ancestry Group, Exome, Exons, Female, Gene Deletion, Golgi Apparatus, Hispanic Americans, Homozygote, Humans, Infant, Male, Molecular Sequence Data, Muscle Weakness, Pedigree, Rhabdomyolysis}, issn = {1537-6605}, doi = {10.1016/j.ajhg.2015.12.008}, author = {Lalani, Seema R and Liu, Pengfei and Rosenfeld, Jill A and Watkin, Levi B and Chiang, Theodore and Leduc, Magalie S and Zhu, Wenmiao and Ding, Yan and Pan, Shujuan and Vetrini, Francesco and Miyake, Christina Y and Shinawi, Marwan and Gambin, Tomasz and Eldomery, Mohammad K and Akdemir, Zeynep Hande Coban and Emrick, Lisa and Wilnai, Yael and Schelley, Susan and Koenig, Mary Kay and Memon, Nada and Farach, Laura S and Coe, Bradley P and Azamian, Mahshid and Hernandez, Patricia and Zapata, Gladys and Jhangiani, Shalini N and Muzny, Donna M and Lotze, Timothy and Clark, Gary and Wilfong, Angus and Northrup, Hope and Adesina, Adekunle and Bacino, Carlos A and Scaglia, Fernando and Bonnen, Penelope E and Crosson, Jane and Duis, Jessica and Maegawa, Gustavo H B and Coman, David and Inwood, Anita and McGill, Jim and Boerwinkle, Eric and Graham, Brett and Beaudet, Art and Eng, Christine M and Hanchard, Neil A and Xia, Fan and Orange, Jordan S and Gibbs, Richard A and Lupski, James R and Yang, Yaping} }