@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 {935, title = {Genotypic diversity and phenotypic spectrum of infantile liver failure syndrome type 1 due to variants in LARS1.}, journal = {Genet Med}, volume = {22}, year = {2020}, month = {2020 11}, pages = {1863-1873}, abstract = {

PURPOSE: Biallelic variants in LARS1, coding for the cytosolic leucyl-tRNA synthetase, cause infantile liver failure syndrome 1 (ILFS1). Since its description in 2012, there has been no systematic analysis of the clinical spectrum and genetic findings.

METHODS: Individuals with biallelic variants in LARS1 were included through an international, multicenter collaboration including novel and previously published patients. Clinical variables were analyzed and functional studies were performed in patient-derived fibroblasts.

RESULTS: Twenty-five individuals from 15 families were ascertained including 12 novel patients with eight previously unreported variants. The most prominent clinical findings are recurrent elevation of liver transaminases up to liver failure and encephalopathic episodes, both triggered by febrile illness. Magnetic resonance image (MRI) changes during an encephalopathic episode can be consistent with metabolic stroke. Furthermore, growth retardation, microcytic anemia, neurodevelopmental delay, muscular hypotonia, and infection-related seizures are prevalent. Aminoacylation activity is significantly decreased in all patient cells studied upon temperature elevation in vitro.

CONCLUSION: ILFS1 is characterized by recurrent elevation of liver transaminases up to liver failure in conjunction with abnormalities of growth, blood, nervous system, and musculature. Encephalopathic episodes with seizures can occur independently from liver crises and may present with metabolic stroke.

}, keywords = {Humans, Liver Failure, Muscle Hypotonia, Mutation, Seizures}, issn = {1530-0366}, doi = {10.1038/s41436-020-0904-4}, author = {Lenz, Dominic and Smith, Desir{\'e}e E C and Crushell, Ellen and Husain, Ralf A and Salomons, Gajja S and Alhaddad, Bader and Bernstein, Jonathan A and Bianzano, Alyssa and Biskup, Saskia and Brennenstuhl, Heiko and Caldari, Dominique and Dikow, Nicola and Haack, Tobias B and Hanson-Kahn, Andrea and Harting, Inga and Horn, Denise and Hughes, Joanne and Huijberts, Maya and Isidor, Bertrand and Kathemann, Simone and Kopajtich, Robert and Kotzaeridou, Urania and K{\"u}ry, S{\'e}bastien and Lainka, Elke and Laugwitz, Lucia and Lupski, James R and Posey, Jennifer E and Reynolds, Claire and Rosenfeld, Jill A and Schr{\"o}ter, Julian and Vansenne, Fleur and Wagner, Matias and Wei{\ss}, Claudia and Wolffenbuttel, Bruce H R and Wortmann, Saskia B and K{\"o}lker, Stefan and Hoffmann, Georg F and Prokisch, Holger and Mendes, Marisa I and Staufner, Christian} }