@article {756, title = {Congenital myasthenic syndrome with mild intellectual disability caused by a recurrent SLC25A1 variant.}, journal = {Eur J Hum Genet}, volume = {28}, year = {2020}, month = {2020 03}, pages = {373-377}, abstract = {

Congenital myasthenic syndromes (CMS) are a clinically and genetically heterogeneous group of disorders caused by mutations which lead to impaired neuromuscular transmission. SLC25A1 encodes a mitochondrial citrate carrier, associated mainly with the severe neurometabolic disease combined D-2- and L-2-hydroxyglutaric aciduria (D/L-2-HGA). We previously reported a single family with a homozygous missense variant in SLC25A1 with a phenotype restricted to relatively mild CMS with intellectual disability, but to date no additional cases of this CMS subtype had been reported. Here, we performed whole exome sequencing (WES) in three additional and unrelated families presenting with CMS and mild intellectual disability to identify the underlying causative gene. The WES analysis revealed the presence of a homozygous c.740G>A; p.(Arg247Gln) missense SLC25A1 variant, the same SLC25A1 variant as identified in the original family with this phenotype. Electron microscopy of muscle from two cases revealed enlarged and accumulated mitochondria. Haplotype analysis performed in two unrelated families suggested that this variant is a result of recurrent mutation and not a founder effect. This suggests that p.(Arg247Gln) is associated with a relatively mild CMS phenotype with subtle mitochondrial abnormalities, while other variants in this gene cause more severe neurometabolic disease. In conclusion, the p.(Arg247Gln) SLC25A1 variant should be considered in patients presenting with a presynaptic CMS phenotype, particularly with accompanying intellectual disability.

}, keywords = {Adult, Female, Haplotypes, Homozygote, Humans, Intellectual Disability, Male, Mitochondrial Proteins, Muscle, Skeletal, Mutation, Missense, Myasthenic Syndromes, Congenital, Organic Anion Transporters}, issn = {1476-5438}, doi = {10.1038/s41431-019-0506-2}, author = {Balaraju, Sunitha and Topf, Ana and McMacken, Grace and Kumar, Veeramani Preethish and Pechmann, Astrid and Roper, Helen and Vengalil, Seena and Polavarapu, Kiran and Nashi, Saraswati and MAHjan, Niranjan Prakash and Barbosa, Ines A and Deshpande, Charu and Taylor, Robert W and Cossins, Judith and Beeson, David and Laurie, Steven and Kirschner, Janbernd and Horvath, Rita and McFarland, Robert and Nalini, Atchayaram and Lochm{\"u}ller, Hanns} } @article {755, title = {Severe neurodevelopmental disease caused by a homozygous TLK2 variant.}, journal = {Eur J Hum Genet}, volume = {28}, year = {2020}, month = {2020 03}, pages = {383-387}, abstract = {

A distinct neurodevelopmental phenotype characterised mainly by mild motor and language delay and facial dysmorphism, caused by heterozygous de novo or dominant variants in the TLK2 gene has recently been described. All cases reported carried either truncating variants located throughout the gene, or missense changes principally located at the C-terminal end of the protein mostly resulting in haploinsufficiency of TLK2. Through whole exome sequencing, we identified a homozygous missense variant in TLK2 in a patient showing more severe symptoms than those previously described, including cerebellar vermis hypoplasia and West syndrome. Both parents are heterozygous for the variant and clinically unaffected highlighting that recessive variants in TLK2 can also be disease causing and may act through a different pathomechanism.

}, keywords = {Adult, Cerebellum, Child, Developmental Disabilities, Female, Heterozygote, Homozygote, Humans, Infant, Male, Mutation, Missense, Nervous System Malformations, Pedigree, Protein Kinases, Spasms, Infantile}, issn = {1476-5438}, doi = {10.1038/s41431-019-0519-x}, author = {Topf, Ana and Oktay, Yavuz and Balaraju, Sunitha and Yilmaz, Elmasnur and Sonmezler, Ece and Yis, Uluc and Laurie, Steven and Thompson, Rachel and Roos, Andreas and MacArthur, Daniel G and Yaramis, Ahmet and G{\"u}ng{\"o}r, Serdal and Lochm{\"u}ller, Hanns and Hiz, Semra and Horvath, Rita} } @article {487, title = {Detection of variants in dystroglycanopathy-associated genes through the application of targeted whole-exome sequencing analysis to a large cohort of patients with unexplained limb-girdle muscle weakness.}, journal = {Skelet Muscle}, volume = {8}, year = {2018}, month = {2018 07 30}, pages = {23}, abstract = {

BACKGROUND: Dystroglycanopathies are a clinically and genetically heterogeneous group of disorders that are typically characterised by limb-girdle muscle weakness. Mutations in 18 different genes have been associated with dystroglycanopathies, the encoded proteins of which typically modulate the binding of α-dystroglycan to extracellular matrix ligands by altering its glycosylation. This results in a disruption of the structural integrity of the myocyte, ultimately leading to muscle degeneration.

METHODS: Deep phenotypic information was gathered using the PhenoTips online software for 1001 patients with unexplained limb-girdle muscle weakness from 43 different centres across 21 European and Middle Eastern countries. Whole-exome sequencing with at least 250~ng DNA was completed using an Illumina exome capture and a 38~Mb baited target. Genes known to be associated with dystroglycanopathies were analysed for disease-causing variants.

RESULTS: Suspected pathogenic variants were detected in DPM3, ISPD, POMT1 and FKTN in one patient each, in POMK in two patients, in GMPPB in three patients, in FKRP in eight patients and in POMT2 in ten patients. This indicated a frequency of 2.7\% for the disease group within the cohort of 1001 patients with unexplained limb-girdle muscle weakness. The phenotypes of the 27 patients were highly variable, yet with a fundamental presentation of proximal muscle weakness and elevated serum creatine kinase.

CONCLUSIONS: Overall, we have identified 27 patients with suspected pathogenic variants in dystroglycanopathy-associated genes. We present evidence for the genetic and phenotypic diversity of the dystroglycanopathies as a disease group, while also highlighting the advantage of incorporating next-generation sequencing into the diagnostic pathway of rare diseases.

}, keywords = {Adolescent, Adult, Aged, Aged, 80 and over, Child, Child, Preschool, Dystroglycans, Female, Genetic Predisposition to Disease, Genetic Variation, Glycosylation, Heterozygote, Homozygote, Humans, Male, Middle Aged, Muscle Proteins, Muscular Dystrophies, Limb-Girdle, Mutation, Phenotype, Whole Exome Sequencing, Young Adult}, issn = {2044-5040}, doi = {10.1186/s13395-018-0170-1}, author = {Johnson, Katherine and Bertoli, Marta and Phillips, Lauren and Topf, Ana and Van den Bergh, Peter and Vissing, John and Witting, Nanna and Nafissi, Shahriar and Jamal-Omidi, Shirin and {\L}usakowska, Anna and Kostera-Pruszczyk, Anna and Potulska-Chromik, Anna and Deconinck, Nicolas and Wallgren-Pettersson, Carina and Strang-Karlsson, Sonja and Colomer, Jaume and Claeys, Kristl G and De Ridder, Willem and Baets, Jonathan and von der Hagen, Maja and Fern{\'a}ndez-Torr{\'o}n, Roberto and Zulaica Ijurco, Miren and Espinal Valencia, Juan Bautista and Hahn, Andreas and Durmus, Hacer and Willis, Tracey and Xu, Liwen and Valkanas, Elise and Mullen, Thomas E and Lek, Monkol and MacArthur, Daniel G and Straub, Volker} } @article {443, title = {Complex phenotypes associated with STIM1 mutations in both coiled coil and EF-hand domains.}, journal = {Neuromuscul Disord}, volume = {27}, year = {2017}, month = {2017 Sep}, pages = {861-872}, abstract = {

Dominant mutations in STIM1 are a cause of three allelic conditions: tubular aggregate myopathy, Stormorken syndrome (a complex phenotype including myopathy, hyposplenism, hypocalcaemia and bleeding diathesis), and a platelet dysfunction disorder, York platelet syndrome. Previous reports have suggested a genotype-phenotype correlation with mutations in the N-terminal EF-hand domain associated with tubular aggregate myopathy, and a common mutation at p.R304W in a coiled coil domain associated with Stormorken syndrome. In this study individuals with STIM1 variants were identified by exome sequencing or STIM1 direct sequencing, and assessed for neuromuscular, haematological and biochemical evidence of the allelic disorders of STIM1. STIM1 mutations were investigated by fibroblast calcium imaging and 3D modelling. Six individuals with STIM1 mutations, including two novel mutations (c.262A>G (p.S88G) and c.911G>A (p.R304Q)), were identified. Extra-neuromuscular symptoms including thrombocytopenia, platelet dysfunction, hypocalcaemia or hyposplenism were present in 5/6 patients with mutations in both the EF-hand and CC domains. 3/6 patients had psychiatric disorders, not previously reported in STIM1 disease. Review of published STIM1 patients (n = 49) confirmed that neuromuscular symptoms are present in most patients. We conclude that the phenotype associated with activating STIM1 mutations frequently includes extra-neuromuscular features such as hypocalcaemia, hypo-/asplenia and platelet dysfunction regardless of mutation domain.

}, keywords = {Adult, Blood Platelet Disorders, Calcium, Cell Culture Techniques, DNA Mutational Analysis, Dyslexia, Erythrocytes, Abnormal, Family Health, Female, Fibroblasts, Genetic Association Studies, Humans, Ichthyosis, Magnetic Resonance Imaging, Male, Microscopy, Electron, Middle Aged, Migraine Disorders, Miosis, Models, Molecular, Muscle Fatigue, Muscle, Skeletal, Mutation, Myopathies, Structural, Congenital, NAD, Neoplasm Proteins, Spleen, Stromal Interaction Molecule 1}, issn = {1873-2364}, doi = {10.1016/j.nmd.2017.05.002}, author = {Harris, Elizabeth and Burki, Umar and Marini-Bettolo, Chiara and Neri, Marcella and Scotton, Chiara and Hudson, Judith and Bertoli, Marta and Evangelista, Teresinha and Vroling, Bas and Polvikoski, Tuomo and Roberts, Mark and Topf, Ana and Bushby, Kate and McArthur, Daniel and Lochm{\"u}ller, Hanns and Ferlini, Alessandra and Straub, Volker and Barresi, Rita} } @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} }