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Background: Defects in GNAO1, the gene encoding the major neuronal G‐protein Gαo, are related to neurodevelopmental disorders, epilepsy, and movement disorders. Nevertheless, there is a poor understanding of how molecular mechanisms explain the different phenotypes. Objectives: We aimed to analyze the clinical phenotype and the molecular characterization of GNAO1‐related disorders. Methods: Patients were recruited in collaboration with the Spanish GNAO1 Association. For patient phenotyping, direct clinical evaluation, analysis of homemade‐videos, and an online questionnaire completed by families were analyzed. We studied Gαo cellular expression, the interactions of the partner proteins, and binding to guanosine triphosphate (GTP) and G‐protein‐coupled receptors (GPCRs). Results: Eighteen patients with GNAO1 genetic defects had a complex neurodevelopmental disorder, epilepsy, central hypotonia, and movement disorders. Eleven patients showed neurological deterioration, recurrent hyperkinetic crisis with partial recovery, and secondary complications leading to death in three cases. Deep brain stimulation improved hyperkinetic crisis, but had inconsistent benefits in dystonia. The molecular defects caused by pathogenic Gαo were aberrant GTP binding and hydrolysis activities, an inability to interact with cellular binding partners, and reduced coupling to GPCRs. Decreased localization of Gαo in the plasma membrane was correlated with the phenotype of "developmental and epileptic encephalopathy 17." We observed a genotype–phenotype correlation, pathogenic variants in position 203 were related to developmental and epileptic encephalopathy, whereas those in position 209 were related to neurodevelopmental disorder with involuntary movements. Milder phenotypes were associated with other molecular defects such as del.16q12.2q21 and I344del. Conclusion: We highlight the complexity of the motor phenotype, which is characterized by fluctuations throughout the day, and hyperkinetic crisis with a distinct post‐hyperkinetic crisis state. We confirm a molecular‐based genotype–phenotype correlation for specific variants. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Anoctamin 3 (ANO3) belongs to a family of transmembrane proteins that form phospholipid scramblases and ion channels. A large number of ANO3 variants were identified as the cause of craniocervical dystonia, but the underlying pathogenic mechanisms remain obscure. It was suggested that ANO3 variants may dysregulate intracellular Ca2+ signalling, as variants in other Ca2+ regulating proteins like hippocalcin were also identified as a cause of dystonia. In this study, we conducted a comprehensive evaluation of the clinical, radiological and molecular characteristics of four individuals from four families who carried heterozygous variants in ANO3. The median age at follow-up was 6.6 years (ranging from 3.8 to 8.7 years). Three individuals presented with hypotonia and motor developmental delay. Two patients exhibited generalized progressive dystonia, while one patient presented with paroxysmal dystonia. Additionally, another patient exhibited early dyskinetic encephalopathy. One patient underwent bipallidal deep brain stimulation (DBS) and showed a mild but noteworthy response, while another patient is currently being considered for DBS treatment. Neuroimaging analysis of brain MRI studies did not reveal any specific abnormalities. The molecular spectrum included two novel ANO3 variants (V561L and S116L) and two previously reported ANO3 variants (A599D and S651N). As anoctamins are suggested to affect intracellular Ca2+ signals, we compared Ca2+ signalling and activation of ion channels in cells expressing wild-type ANO3 and cells expressing anoctamin variants. Novel V561L and S116L variants were compared with previously reported A599D and S651N variants and with wild-type ANO3 expressed in fibroblasts isolated from patients or when overexpressed in HEK293 cells. We identified ANO3 as a Ca2+-activated phospholipid scramblase that also conducts ions. Impaired Ca2+ signalling and compromised activation of Ca2+-dependent K+ channels were detected in cells expressing ANO3 variants. In the brain striatal cells of affected patients, impaired activation of KCa3.1 channels due to compromised Ca2+ signals may lead to depolarized membrane voltage and neuronal hyperexcitability and may also lead to reduced cellular viability, as shown in the present study. In conclusion, our study reveals the association between ANO3 variants and paroxysmal dystonia, representing the first reported link between these variants and this specific dystonic phenotype. We demonstrate that ANO3 functions as a Ca2+-activated phospholipid scramblase and ion channel; cells expressing ANO3 variants exhibit impaired Ca2+ signalling and compromised activation of Ca2+-dependent K+ channels. These findings provide a mechanism for the observed clinical manifestations and highlight the importance of ANO3 for neuronal excitability and cellular viability. [ABSTRACT FROM AUTHOR]

Objective: GNAO1‐related disorders (OMIM #615473 and #617493), caused by variants in the GNAO1 gene, are characterized by developmental delay or intellectual disability, hypotonia, movement disorders, and epilepsy. Neither a genotype–phenotype correlation nor a clear severity score have been established for this disorder. The objective of this prospective and retrospective observational study was to develop a severity score for GNAO1‐related disorders, and to delineate the correlation between the underlying molecular mechanisms and clinical severity. Methods: A total of 16 individuals with GNAO1‐related disorders harboring 12 distinct missense variants, including four novel variants (p.K46R, p.T48I, p.R209P, and p.L235P), were examined with repeated clinical assessments, video‐electroencephalogram monitoring, and brain magnetic resonance imaging. The molecular pathology of each variant was delineated using a molecular deconvoluting platform. Results: The patients displayed a wide variability in the severity of their symptoms. This heterogeneity was well represented in the GNAO1‐related disorders severity score, with a broad range of results. Patients with the same variant had comparable severity scores, indicating that differences in disease profiles are not due to interpatient variability, but rather, to unique disease mechanisms. Moreover, we found a significant correlation between clinical severity scores and molecular mechanisms. Interpretation: The clinical score proposed here provides further insight into the correlation between pathophysiology and phenotypic severity in GNAO1‐related disorders. We found that each variant has a unique profile of clinical phenotypes and pathological molecular mechanisms. These findings will contribute to better understanding GNAO1‐related disorders. Additionally, the severity score will facilitate standardization of patients categorization and assessment of response to therapies in development. ANN NEUROL 2023;94:987–1004 [ABSTRACT FROM AUTHOR]

Background: NKX2-1-related disorders have a prevalence of 1:500,000 and are therefore considered a rare condition according to the European Commission's definition. The European Reference Network of Rare Neurological Disorders is developing the first clinical practice guideline on the management of this condition, with the support of the Andalusian Health Technology Assessment Area, Endo-ERN, ERN-Lung and Imegen, within the framework of the ERNs Guidelines programme (DG SANTE/2018/B3/030). Within the scope of this programme, it becomes necessary to explore the patient perspective in order to include it in the ongoing clinical practice guideline and accompanying patient information booklet. Methods and analysis: This study will use qualitative methods to explore the values, preferences and information needs of patient with NKX2-1-related disorders and their caregivers. Participants will come from a variety of countries throughout Europe. One focus group and four semi-structured interviews will be conducted. Pairs will analyse the data using Grounded Theory. The Andalusian Regional Ministry of Health's Ethics Coordinating Committee for Biomedical Research (Sevilla, Andalucía, Spain) has approved this study protocol (29/03/2022). Discussion: This is the first study to explore the values, preferences, and information needs of patients with NKX2-1-related disorders. The proposed study's findings will contribute to the generation of useful knowledge that will provide guidance to improve the care given to patients with the studied condition. While this study will provide valuable insights into the perspectives of patients with NKX2-1-related disorders, the findings are unlikely to be generalizable to patients with other conditions. [ABSTRACT FROM AUTHOR]

One percent of patients with a Huntington's disease (HD) phenotype do not have the Huntington (HTT) gene mutation. These are known as HD phenocopies. Their diagnosis is still a challenge. Our objective is to provide a diagnostic approach to HD phenocopies based on medical expertise and a review of the literature. We employed two complementary approaches sequentially: a review of the literature and two surveys analyzing the daily clinical practice of physicians who are experts in movement disorders. The review of the literature was conducted from 1993 to 2020, by extracting articles about chorea or HD-like disorders from the database Pubmed, yielding 51 articles, and analyzing 20 articles in depth to establish the surveys. Twenty-eight physicians responded to the first survey exploring the red flags suggestive of specific disease entities. Thirty-three physicians completed the second survey which asked for the classification of paraclinical tests according to their diagnostic significance. The analysis of the results of the second survey used four different clustering algorithms and the density-based clustering algorithm DBSCAN to classify the paraclinical tests into 1st, 2nd, and 3rd-line recommendations. In addition, we included suggestions from members of the European Reference Network-Rare Neurological Diseases (ERN-RND Chorea & Huntington disease group). Finally, we propose guidance that integrate the detection of clinical red flags with a classification of paraclinical testing options to improve the diagnosis of HD phenocopies. [ABSTRACT FROM AUTHOR]

The neurological phenotype of 3‐hydroxyisobutyryl‐CoA hydrolase (HIBCH) and short‐chain enoyl‐CoA hydratase (SCEH) defects is expanding and natural history studies are necessary to improve clinical management. From 42 patients with Leigh syndrome studied by massive parallel sequencing, we identified five patients with SCEH and HIBCH deficiency. Fourteen additional patients were recruited through collaborations with other centres. In total, we analysed the neurological features and mutation spectrum in 19 new SCEH/HIBCH patients. For natural history studies and phenotype to genotype associations we also included 70 previously reported patients. The 19 newly identified cases presented with Leigh syndrome (SCEH, n = 11; HIBCH, n = 6) and paroxysmal dystonia (SCEH, n = 2). Basal ganglia lesions (18 patients) were associated with small cysts in the putamen/pallidum in half of the cases, a characteristic hallmark for diagnosis. Eighteen pathogenic variants were identified, 11 were novel. Among all 89 cases, we observed a longer survival in HIBCH compared to SCEH patients, and in HIBCH patients carrying homozygous mutations on the protein surface compared to those with variants inside/near the catalytic region. The SCEH p.(Ala173Val) change was associated with a milder form of paroxysmal dystonia triggered by increased energy demands. In a child harbouring SCEH p.(Ala173Val) and the novel p.(Leu123Phe) change, an 83.6% reduction of the protein was observed in fibroblasts. The SCEH and HIBCH defects in the catabolic valine pathway were a frequent cause of Leigh syndrome in our cohort. We identified phenotype and genotype associations that may help predict outcome and improve clinical management. [ABSTRACT FROM AUTHOR]

While rare diseases (RDs) are by definition of low prevalence, the total number of patients suffering from an RD is high, and the majority of them have neurologic manifestations, involving central, peripheral nerve, and muscle. In 2017, 24 European Reference Networks (ERNs), each focusing on a specific group of rare or low-prevalence complex diseases, were formed to improve the care for patients with an RD. One major aim is to have "the knowledge travel instead of the patient," which has been put into practice by the implementation of the Clinical Patient Management System (CPMS) that enables clinicians to perform pan-European virtual consultations. The European Reference Network for Rare Neurological Diseases (ERN-RND) provides an infrastructure for knowledge sharing and care coordination for patients affected by a rare neurological disease (RND) involving the most common central nervous system pathological conditions. It covers the following disease groups: (i) Cerebellar Ataxias and Hereditary Spastic Paraplegias; (ii) Huntington's disease and Other Choreas; (iii) Frontotemporal dementia; (iv) Dystonia, (non-epileptic) paroxysmal disorders, and Neurodegeneration with Brain Iron Accumulation; (v) Leukoencephalopathies; and (vi) Atypical Parkinsonian Syndromes. At the moment, it unites 32 expert centers and 10 affiliated partners in 21 European countries, as well as patient representatives, but will soon cover nearly all countries of the European Union as a result of the ongoing expansion process. Disease expert groups developed and consented on diagnostic flowcharts and disease scales to assess the different aspects of RNDs. ERN-RND has started to discuss diagnostically unclear patients in the CPMS, is one of four ERNs that serve as foundation of Solve-RD, and has established an RND training and education program. The network will facilitate trial readiness through the establishment of an ERN-RND registry with a minimal data of all patients seen at the ERN-RND centers, thus providing a unique overview of existing genotype-based cohorts. The overall aim of the ERNs is to improve access for patients with RDs to quality diagnosis, care, and treatment. Based on this objective, ERNs are monitored by the European Commission on a regular basis to provide transparency and reassurance to the RD community and the general public. [ABSTRACT FROM AUTHOR]

Anoctamin 3 (ANO3) belongs to a family of transmembrane proteins that form phospholipid scramblases and ion channels. A large number of ANO3 variants were identified as the cause of craniocervical dystonia, but the underlying pathogenic mechanisms remain obscure. It was suggested that ANO3 variants may dysregulate intracellular Ca2+ signalling, as variants in other Ca2+ regulating proteins like hippocalcin were also identified as a cause of dystonia. In this study, we conducted a comprehensive evaluation of the clinical, radiological and molecular characteristics of four individuals from four families who carried heterozygous variants in ANO3. The median age at follow-up was 6.6 years (ranging from 3.8 to 8.7 years). Three individuals presented with hypotonia and motor developmental delay. Two patients exhibited generalized progressive dystonia, while one patient presented with paroxysmal dystonia. Additionally, another patient exhibited early dyskinetic encephalopathy. One patient underwent bipallidal deep brain stimulation (DBS) and showed a mild but noteworthy response, while another patient is currently being considered for DBS treatment. Neuroimaging analysis of brain MRI studies did not reveal any specific abnormalities. The molecular spectrum included two novel ANO3 variants (V561L and S116L) and two previously reported ANO3 variants (A599D and S651N). As anoctamins are suggested to affect intracellular Ca2+ signals, we compared Ca2+ signalling and activation of ion channels in cells expressing wild-type ANO3 and cells expressing anoctamin variants. Novel V561L and S116L variants were compared with previously reported A599D and S651N variants and with wild-type ANO3 expressed in fibroblasts isolated from patients or when overexpressed in HEK293 cells. We identified ANO3 as a Ca2+-activated phospholipid scramblase that also conducts ions. Impaired Ca2+ signalling and compromised activation of Ca2+-dependent K+ channels were detected in cells expressing ANO3 variants. In the brain striatal cells of affected patients, impaired activation of KCa3.1 channels due to compromised Ca2+ signals may lead to depolarized membrane voltage and neuronal hyperexcitability and may also lead to reduced cellular viability, as shown in the present study. In conclusion, our study reveals the association between ANO3 variants and paroxysmal dystonia, representing the first reported link between these variants and this specific dystonic phenotype. We demonstrate that ANO3 functions as a Ca2+-activated phospholipid scramblase and ion channel; cells expressing ANO3 variants exhibit impaired Ca2+ signalling and compromised activation of Ca2+-dependent K+ channels. These findings provide a mechanism for the observed clinical manifestations and highlight the importance of ANO3 for neuronal excitability and cellular viability., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Pathogenic variants in SCN8A are associated with a broad phenotypic spectrum, including Self-Limiting Familial Infantile Epilepsy (SeLFIE), characterized by infancy-onset age-related seizures with normal development and cognition. Movement disorders, particularly paroxysmal kinesigenic dyskinesia typically arising after puberty, may represent another core symptom. We present the case of a 1-year-old girl with a familial disposition to self-limiting focal seizures from the maternal side and early-onset orofacial movement disorders associated with SCN8A-SeLFIE. Brain MRI was normal. Genetic testing revealed a maternally inherited SCN8A variant [c.4447G > A; p.(Glu1483Lys)]. After the introduction of valproic acid, she promptly achieved seizure control as well as complete remission of strabismus and a significant decrease in episodes of tongue deviation. Family history, genetic findings, and epilepsy phenotype are consistent with SCN8A-SeLFIE. Movement disorders are an important part of the SCN8A phenotypic spectrum, and this case highlights the novel early-onset orofacial movement disorders associated with this condition. The episodes of tongue deviation and protrusion suggest focal oromandibular (lingual) dystonia. Additionally, while infantile strabismus or esophoria is a common finding in healthy individuals, our case raises the possibility of an ictal origin of the strabismus. This study underscores the importance of recognizing and addressing movement disorders in SCN8A-SeLFIE patients, particularly the rare early-onset orofacial manifestations. It adds to the growing body of knowledge regarding the diverse clinical presentations of SCN8A-associated disorders and suggests potential avenues for clinical management and further research., (© 2024 The Authors. Epileptic Disorders published by Wiley Periodicals LLC on behalf of International League Against Epilepsy.)

Pathogenic variants in KANSL1 and 17q21.31 microdeletions are causative of Koolen-de Vries syndrome (KdVS), a neurodevelopmental syndrome with characteristic facial dysmorphia. Our previous work has shown that syndromic conditions caused by pathogenic variants in epigenetic regulatory genes have identifiable patterns of DNA methylation (DNAm) change: DNAm signatures or episignatures. Given the role of KANSL1 in histone acetylation, we tested whether variants underlying KdVS are associated with a DNAm signature. We profiled whole-blood DNAm for 13 individuals with KANSL1 variants, four individuals with 17q21.31 microdeletions, and 21 typically developing individuals, using Illumina's Infinium EPIC array. In this study, we identified a robust DNAm signature of 456 significant CpG sites in 8 individuals with KdVS, a pattern independently validated in an additional 7 individuals with KdVS. We also demonstrate the diagnostic utility of the signature and classify two KANSL1 VUS as well as four variants in individuals with atypical clinical presentation. Lastly, we investigated tissue-specific DNAm changes in fibroblast cells from individuals with KdVS. Collectively, our findings contribute to the understanding of the epigenetic landscape related to KdVS and aid in the diagnosis and classification of variants in this structurally complex genomic region., (© 2024. The Author(s).)

Phelan-McDermid syndrome (PMS, OMIM# 606232) results from either different rearrangements at the distal region of the long arm of chromosome 22 (22q13.3) or pathogenic sequence variants in the SHANK3 gene. SHANK3 codes for a structural protein that plays a central role in the formation of the postsynaptic terminals and the maintenance of synaptic structures. Clinically, patients with PMS often present with global developmental delay, absent or severely delayed speech, neonatal hypotonia, minor dysmorphic features, and autism spectrum disorders (ASD), among other findings. Here, we describe a cohort of 210 patients with genetically confirmed PMS. We observed multiple variant types, including a significant number of small deletions (<0.5 Mb, 64/189) and SHANK3 sequence variants (21 cases). We also detected multiple types of rearrangements among microdeletion cases, including a significant number with post-zygotic mosaicism (9.0%, 17/189), ring chromosome 22 (10.6%, 20/189), unbalanced translocations ( de novo or inherited, 6.4%), and additional rearrangements at 22q13 (6.3%, 12/189) as well as other copy number variations in other chromosomes, unrelated to 22q deletions (14.8%, 28/189). We compared the clinical and genetic characteristics among patients with different sizes of deletions and with SHANK3 variants . Our findings suggest that SHANK3 plays an important role in this syndrome but is probably not uniquely responsible for all the spectrum features in PMS. We emphasize that only an adequate combination of different molecular and cytogenetic approaches allows an accurate genetic diagnosis in PMS patients. Thus, a diagnostic algorithm is proposed., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Nevado, García-Miñaúr, Palomares-Bralo, Vallespín, Guillén-Navarro, Rosell, Bel-Fenellós, Mori, Milá, Campo, Barrúz, Santos-Simarro, Obregón, Orellana, Pachajoa, Tenorio, Galán, Cigudosa, Moresco, Saleme, Castillo, Gabau, Pérez-Jurado, Barcia, Martín, Mansilla, Vallcorba, García-Murillo, Cammarata-Scalisi, Gonçalves Pereira, Blanco-Lago, Serrano, Ortigoza-Escobar, Gener, Seidel, Tirado, Lapunzina and Spanish PMS Working Group.)

We investigated the genetic, phenotypic, and interferon status of 46 patients from 37 families with neurological disease due to mutations in ADAR1 . The clinicoradiological phenotype encompassed a spectrum of Aicardi-Goutières syndrome, isolated bilateral striatal necrosis, spastic paraparesis with normal neuroimaging, a progressive spastic dystonic motor disorder, and adult-onset psychological difficulties with intracranial calcification. Homozygous missense mutations were recorded in five families. We observed a p.Pro193Ala variant in the heterozygous state in 22 of 23 families with compound heterozygous mutations. We also ascertained 11 cases from nine families with a p.Gly1007Arg dominant-negative mutation, which occurred de novo in four patients, and was inherited in three families in association with marked phenotypic variability. In 50 of 52 samples from 34 patients, we identified a marked upregulation of type I interferon-stimulated gene transcripts in peripheral blood, with a median interferon score of 16.99 (interquartile range [IQR]: 10.64-25.71) compared with controls (median: 0.93, IQR: 0.57-1.30). Thus, mutations in ADAR1 are associated with a variety of clinically distinct neurological phenotypes presenting from early infancy to adulthood, inherited either as an autosomal recessive or dominant trait. Testing for an interferon signature in blood represents a useful biomarker in this context., Competing Interests: Authors' Contributions: J.H.L. and Y.J.C. collated and reviewed all clinical and radiological data. G.I.R. performed quantitative PCR analysis, with assistance from N.K., M.B., T.A.B., A.C.E.B., M.L.C., A.M.C., C.C., R.C.D., F.R.D., N.D., B. De A., V. De G., C.G.E.L. De G., I.D., C De L., A.E., M.C.F., P.F., A.F., E.F., M.P.G., N.R.G., M.H., M.A.K., N.L., J.-P.S.-M.L., M.A.L., S.S.M., R.M., L.M.-S., G.M., M.M., V.N., S.O., J.D.O.-E., B.P.-D., F.P., K.M.R., M.R., F.R., P.R.-P., A.R., T.I.S., M.B.T., A.T., F.U., N.U., A.V., and A.W. provided clinical samples and critically reviewed clinical and immunological patient data. Y.J.C. conceived the study and wrote the initial draft with the assistance of G.I.R. All authors critically reviewed the article and agreed to its publication. Financial Disclosure None of the authors have any financial disclosure to report., (Georg Thieme Verlag KG Stuttgart · New York.)