@article {918, title = {De novo variants in SNAP25 cause an early-onset developmental and epileptic encephalopathy.}, journal = {Genet Med}, volume = {23}, year = {2021}, month = {2021 04}, pages = {653-660}, abstract = {

PURPOSE: This study aims to provide a comprehensive description of the phenotypic and genotypic spectrum of SNAP25 developmental and epileptic encephalopathy (SNAP25-DEE) by reviewing newly identified and previously reported individuals.

METHODS: Individuals harboring heterozygous missense or loss-of-function variants in SNAP25 were assembled through collaboration with international colleagues, matchmaking platforms, and literature review. For each individual, detailed phenotyping, classification, and structural modeling of the identified variant were performed.

RESULTS: The cohort comprises 23 individuals with pathogenic or likely pathogenic de novo variants in SNAP25. Intellectual disability and early-onset epilepsy were identified as the core symptoms of SNAP25-DEE, with recurrent findings of movement disorders, cerebral visual impairment, and brain atrophy. Structural modeling for all variants predicted possible functional defects concerning SNAP25 or impaired interaction with other components of the SNARE complex.

CONCLUSION: We provide a comprehensive description of SNAP25-DEE with intellectual disability and early-onset epilepsy mostly occurring before the age of two years. These core symptoms and additional recurrent phenotypes show an overlap to genes encoding other components or associated proteins of the SNARE complex such as STX1B, STXBP1, or VAMP2. Thus, these findings advance the concept of a group of neurodevelopmental disorders that may be termed "SNAREopathies."

}, keywords = {Brain Diseases, Child, Preschool, Epilepsy, Humans, Intellectual Disability, Neurodevelopmental Disorders, Phenotype, Synaptosomal-Associated Protein 25}, issn = {1530-0366}, doi = {10.1038/s41436-020-01020-w}, author = {Kl{\"o}ckner, Chiara and Sticht, Heinrich and Zacher, Pia and Popp, Bernt and Babcock, Holly E and Bakker, Dewi P and Barwick, Katy and Bonfert, Michaela V and B{\"o}nnemann, Carsten G and Brilstra, Eva H and Chung, Wendy K and Clarke, Angus J and Devine, Patrick and Donkervoort, Sandra and Fraser, Jamie L and Friedman, Jennifer and Gates, Alyssa and Ghoumid, Jamal and Hobson, Emma and Horvath, Gabriella and Keller-Ramey, Jennifer and Keren, Boris and Kurian, Manju A and Lee, Virgina and Leppig, Kathleen A and Lundgren, Johan and McDonald, Marie T and McLaughlin, Heather M and McTague, Amy and Mefford, Heather C and Mignot, Cyril and Mikati, Mohamad A and Nava, Caroline and Raymond, F Lucy and Sampson, Julian R and Sanchis-Juan, Alba and Shashi, Vandana and Shieh, Joseph T C and Shinawi, Marwan and Slavotinek, Anne and St{\"o}dberg, Tommy and Stong, Nicholas and Sullivan, Jennifer A and Taylor, Ashley C and Toler, Tomi L and van den Boogaard, Marie-Jos{\'e} and van der Crabben, Saskia N and van Gassen, Koen L I and van Jaarsveld, Richard H and Van Ziffle, Jessica and Wadley, Alexandrea F and Wagner, Matias and Wigby, Kristen and Wortmann, Saskia B and Zarate, Yuri A and M{\o}ller, Rikke S and Lemke, Johannes R and Platzer, Konrad} } @article {984, title = {Gain-of-function variants identified in vigabatrin-hypersensitive epileptic encephalopathies.}, journal = {Brain Commun}, volume = {2}, year = {2020}, month = {2020}, pages = {fcaa162}, abstract = {

Variants in the gene encoding the β3-subunit of the γ-aminobutyric acid type A ( receptor are associated with various developmental and epileptic encephalopathies. Typically, these variants cause a loss-of-function molecular phenotype whereby γ-aminobutyric acid has reduced inhibitory effectiveness leading to seizures. Drugs that potentiate inhibitory GABAergic activity, such as nitrazepam, phenobarbital or vigabatrin, are expected to compensate for this and thereby reduce seizure frequency. However, vigabatrin, a drug that inhibits γ-aminobutyric acid transaminase to increase tonic γ-aminobutyric acid currents, has mixed success in treating seizures in patients with variants: some patients experience seizure cessation, but there is hypersensitivity in some patients associated with hypotonia, sedation and respiratory suppression. A variant that responds well to vigabatrin involves a truncation variant (p.Arg194*) resulting in a clear loss-of-function. We hypothesized that patients with a hypersensitive response to vigabatrin may exhibit a different γ-aminobutyric acid A receptor phenotype. To test this hypothesis, we evaluated the phenotype of variants in (p.Glu77Lys and p.Thr287Ile) associated with patients who are clinically hypersensitive to vigabatrin. We introduced the p.Glu77Lys and p.Thr287Ile variants into a concatenated synaptic and extrasynaptic γ-aminobutyric acid A receptor construct, to resemble the γ-aminobutyric acid A receptor expression by a patient heterozygous for the variant. The mRNA of these constructs was injected into oocytes and activation properties of each receptor measured by two-electrode voltage clamp electrophysiology. Results showed an atypical gain-of-function molecular phenotype in the p.Glu77Lys and p.Thr287Ile variants characterized by increased potency of γ-aminobutyric acid A without change to the estimated maximum open channel probability, deactivation kinetics or absolute currents. Modelling of the activation properties of the receptors indicated that either variant caused increased chloride flux in response to low concentrations of γ-aminobutyric acid that mediate tonic currents. We therefore propose that the hypersensitivity reaction to vigabatrin is a result of variants that exacerbate GABAergic tonic currents and caution is required when prescribing vigabatrin. In contrast, drug strategies increasing tonic currents in loss-of-function variants are likely to be a safe and effective therapy. This study demonstrates that functional genomics can explain beneficial and adverse anti-epileptic drug effects, and propose that vigabatrin should be considered in patients with clear loss-of-function variants.

}, issn = {2632-1297}, doi = {10.1093/braincomms/fcaa162}, author = {Absalom, Nathan L and Liao, Vivian W Y and Kothur, Kavitha and Indurthi, Dinesh C and Bennetts, Bruce and Troedson, Christopher and Mohammad, Shekeeb S and Gupta, Sachin and McGregor, Iain S and Bowen, Michael T and Lederer, Damien and Mary, Sandrine and De Waele, Liesbeth and Jansen, Katrien and Gill, Deepak and Kurian, Manju A and McTague, Amy and M{\o}ller, Rikke S and Ahring, Philip K and Dale, Russell C and Chebib, Mary} } @article {920, title = {KMT2B-related disorders: expansion of the phenotypic spectrum and long-term efficacy of deep brain stimulation.}, journal = {Brain}, volume = {143}, year = {2020}, month = {2020 12 05}, pages = {3242-3261}, abstract = {

Heterozygous mutations in KMT2B are associated with an early-onset, progressive and often complex dystonia (DYT28). Key characteristics of typical disease include focal motor features at disease presentation, evolving through a caudocranial pattern into generalized dystonia, with prominent oromandibular, laryngeal and cervical involvement. Although KMT2B-related disease is emerging as one of the most common causes of early-onset genetic dystonia, much remains to be understood about the full spectrum of the disease. We describe a cohort of 53 patients with KMT2B mutations, with detailed delineation of their clinical phenotype and molecular genetic features. We report new disease presentations, including atypical patterns of dystonia evolution and a subgroup of patients with a non-dystonic neurodevelopmental phenotype. In addition to the previously reported systemic features, our study has identified co-morbidities, including the risk of status dystonicus, intrauterine growth retardation, and endocrinopathies. Analysis of this study cohort (n = 53) in tandem with published cases (n = 80) revealed that patients with chromosomal deletions and protein truncating variants had a significantly higher burden of systemic disease (with earlier onset of dystonia) than those with missense variants. Eighteen individuals had detailed longitudinal data available after insertion of deep brain stimulation for medically refractory dystonia. Median age at deep brain stimulation was 11.5 years (range: 4.5-37.0 years). Follow-up after deep brain stimulation ranged from 0.25 to 22 years. Significant improvement of motor function and disability (as assessed by the Burke Fahn Marsden{\textquoteright}s Dystonia Rating Scales, BFMDRS-M and BFMDRS-D) was evident at 6 months, 1 year and last follow-up (motor, P = 0.001, P = 0.004, and P = 0.012; disability, P = 0.009, P = 0.002 and P = 0.012). At 1 year post-deep brain stimulation, >50\% of subjects showed BFMDRS-M and BFMDRS-D improvements of >30\%. In the long-term deep brain stimulation cohort (deep brain stimulation inserted for >5 years, n = 8), improvement of >30\% was maintained in 5/8 and 3/8 subjects for the BFMDRS-M and BFMDRS-D, respectively. The greatest BFMDRS-M improvements were observed for trunk (53.2\%) and cervical (50.5\%) dystonia, with less clinical impact on laryngeal dystonia. Improvements in gait dystonia decreased from 20.9\% at 1 year to 16.2\% at last assessment; no patient maintained a fully independent gait. Reduction of BFMDRS-D was maintained for swallowing (52.9\%). Five patients developed mild parkinsonism following deep brain stimulation. KMT2B-related disease comprises an expanding continuum from infancy to adulthood, with early evidence of genotype-phenotype correlations. Except for laryngeal dysphonia, deep brain stimulation provides a significant improvement in quality of life and function with sustained clinical benefit depending on symptoms distribution.

}, keywords = {Adolescent, Adult, Child, Child, Preschool, Chromosome Deletion, Cohort Studies, Computer Simulation, Deep Brain Stimulation, Disease Progression, Dystonic Disorders, Endocrine System Diseases, Female, Fetal Growth Retardation, Gait Disorders, Neurologic, Histone-Lysine N-Methyltransferase, Humans, Laryngeal Diseases, Male, Mutation, Mutation, Missense, Phenotype, Quality of Life, Treatment Outcome, Young Adult}, issn = {1460-2156}, doi = {10.1093/brain/awaa304}, author = {Cif, Laura and Demailly, Diane and Lin, Jean-Pierre and Barwick, Katy E and Sa, Mario and Abela, Lucia and Malhotra, Sony and Chong, Wui K and Steel, Dora and Sanchis-Juan, Alba and Ngoh, Adeline and Trump, Natalie and Meyer, Esther and Vasques, Xavier and Rankin, Julia and Allain, Meredith W and Applegate, Carolyn D and Attaripour IsfAHni, Sanaz and Baleine, Julien and Balint, Bettina and Bassetti, Jennifer A and Baple, Emma L and Bhatia, Kailash P and Blanchet, Catherine and Burglen, Lydie and Cambonie, Gilles and Seng, Emilie Chan and Bastaraud, Sandra Chantot and Cyprien, Fabienne and Coubes, Christine and d{\textquoteright}Hardemare, Vincent and Doja, Asif and Dorison, Nathalie and Doummar, Diane and Dy-Hollins, Marisela E and Farrelly, Ellyn and FitzPatrick, David R and Fearon, Conor and Fieg, Elizabeth L and Fogel, Brent L and Forman, Eva B and Fox, Rachel G and Gahl, William A and Galosi, Serena and Gonzalez, Victoria and Graves, Tracey D and Gregory, Allison and Hallett, Mark and Hasegawa, Harutomo and Hayflick, Susan J and Hamosh, Ada and Hully, Marie and Jansen, Sandra and Jeong, Suh Young and Krier, Joel B and Krystal, Sidney and Kumar, Kishore R and Laurencin, Chlo{\'e} and Lee, Hane and Lesca, Gaetan and Fran{\c c}ois, Laurence Lion and Lynch, Timothy and MAHnt, Neil and Martinez-Agosto, Julian A and Milesi, Christophe and Mills, Kelly A and Mondain, Michel and Morales-Briceno, Hugo and Ostergaard, John R and Pal, Swasti and Pallais, Juan C and Pavillard, Fr{\'e}d{\'e}rique and Perrigault, Pierre-Francois and Petersen, Andrea K and Polo, Gustavo and Poulen, Gaetan and Rinne, Tuula and Roujeau, Thomas and Rogers, Caleb and Roubertie, Agathe and SAHgian, Michelle and Schaefer, Elise and Selim, Laila and Selway, Richard and Sharma, Nutan and Signer, Rebecca and Soldatos, Ariane G and Stevenson, David A and Stewart, Fiona and Tchan, Michel and Verma, Ishwar C and de Vries, Bert B A and Wilson, Jenny L and Wong, Derek A and Zaitoun, Raghda and Zhen, Dolly and Znaczko, Anna and Dale, Russell C and de Gusm{\~a}o, Claudio M and Friedman, Jennifer and Fung, Victor S C and King, Mary D and Mohammad, Shekeeb S and Rohena, Luis and Waugh, Jeff L and Toro, Camilo and Raymond, F Lucy and Topf, Maya and Coubes, Philippe and Gorman, Kathleen M and Kurian, Manju A} } @article {610, title = {SYT1-associated neurodevelopmental disorder: a case series.}, journal = {Brain}, volume = {141}, year = {2018}, month = {2018 Sep 01}, pages = {2576-2591}, abstract = {

Synaptotagmin 1 (SYT1) is a critical mediator of fast, synchronous, calcium-dependent neurotransmitter release and also modulates synaptic vesicle endocytosis. This paper describes 11 patients with de novo heterozygous missense mutations in SYT1. All mutations alter highly conserved residues, and cluster in two regions of the SYT1 C2B domain at positions Met303 (M303K), Asp304 (D304G), Asp366 (D366E), Ile368 (I368T) and Asn371 (N371K). Phenotypic features include infantile hypotonia, congenital ophthalmic abnormalities, childhood-onset hyperkinetic movement disorders, motor stereotypies, and developmental delay varying in severity from moderate to profound. Behavioural characteristics include sleep disturbance and episodic agitation. Absence of epileptic seizures and normal orbitofrontal head circumference are important negative features. Structural MRI is unremarkable but EEG disturbance is universal, characterized by intermittent low frequency high amplitude oscillations. The functional impact of these five de novo SYT1 mutations has been assessed by expressing rat SYT1 protein containing the equivalent human variants in wild-type mouse primary hippocampal cultures. All mutant forms of SYT1 were expressed at levels approximately equal to endogenous wild-type protein, and correctly localized to nerve terminals at rest, except for SYT1M303K, which was expressed at a lower level and failed to localize at nerve terminals. Following stimulation, SYT1I368T and SYT1N371K relocalized to nerve terminals at least as efficiently as wild-type SYT1. However, SYT1D304G and SYT1D366E failed to relocalize to nerve terminals following stimulation, indicative of impairments in endocytic retrieval and trafficking of SYT1. In addition, the presence of SYT1 variants at nerve terminals induced a slowing of exocytic rate following sustained action potential stimulation. The extent of disturbance to synaptic vesicle kinetics is mirrored by the severity of the affected individuals{\textquoteright} phenotypes, suggesting that the efficiency of SYT1-mediated neurotransmitter release is critical to cognitive development. In summary, de novo dominant SYT1 missense mutations are associated with a recognizable neurodevelopmental syndrome, and further cases can now be diagnosed based on clinical features, electrophysiological signature and mutation characteristics. Variation in phenotype severity may reflect mutation-specific impact on the diverse physiological functions of SYT1.

}, issn = {1460-2156}, doi = {10.1093/brain/awy209}, author = {Baker, Kate and Gordon, Sarah L and Melland, Holly and Bumbak, Fabian and Scott, Daniel J and Jiang, Tess J and Owen, David and Turner, Bradley J and Boyd, Stewart G and Rossi, Mari and Al-Raqad, Mohammed and Elpeleg, Orly and Peck, Dawn and Mancini, Grazia M S and Wilke, Martina and Zollino, Marcella and Marangi, Giuseppe and Weigand, Heike and Borggraefe, Ingo and Haack, Tobias and Stark, Zornitza and Sadedin, Simon and Tan, Tiong Yang and Jiang, Yunyun and Gibbs, Richard A and Ellingwood, Sara and Amaral, Michelle and Kelley, Whitley and Kurian, Manju A and Cousin, Michael A and Raymond, F Lucy} }