Neurogenetics Group

Antwerpen, Belgium

Neurogenetics Group

Antwerpen, Belgium
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PubMed | University of Naples Federico II, University of Arkansas for Medical Sciences, Copenhagen University, Baylor College of Medicine and 9 more.
Type: | Journal: Epilepsia | Year: 2017

To analyze whether KCNQ2 R201C and R201H variants, which show atypical gain-of-function electrophysiologic properties in vitro, have a distinct clinical presentation and outcome.Ten children with heterozygous, de novo KCNQ2 R201C or R201H variants were identified worldwide, using an institutional review board (IRB)-approved KCNQ2 patient registry and database. We reviewed medical records and, where possible, interviewed parents and treating physicians using a structured, detailed phenotype inventory focusing on the neonatal presentation and subsequent course.Nine patients had encephalopathy from birth and presented with prominent startle-like myoclonus, which could be triggered by sound or touch. In seven patients, electroencephalography (EEG) was performed in the neonatal period and showed a burst-suppression pattern. However, myoclonus did not have an EEG correlate. In many patients the paroxysmal movements were misdiagnosed as seizures. Seven patients developed epileptic spasms in infancy. In all patients, EEG showed a slow background and multifocal epileptiform discharges later in life. Other prominent features included respiratory dysfunction (perinatal respiratory failure and/or chronic hypoventilation), hypomyelination, reduced brain volume, and profound developmental delay. One patient had a later onset, and sequencing indicated that a low abundance (~20%) R201C variant had arisen by postzygotic mosaicism.Heterozygous KCNQ2 R201C and R201H gain-of-function variants present with profound neonatal encephalopathy in the absence of neonatal seizures. Neonates present with nonepileptic myoclonus that is often misdiagnosed and treated as seizures. Prognosis is poor. This clinical presentation is distinct from the phenotype associated with loss-of-function variants, supporting the value of in vitro functional screening. These findings suggest that gain-of-function and loss-of-function variants need different targeted therapeutic approaches.

Pawlik B.,Neurogenetics Group | Schluter T.,Neurogenetics Group | Hartwich H.,Neurogenetics Group | Breuel S.,Neurogenetics Group | And 3 more authors.
Brain, Behavior and Evolution | Year: 2017

The neurons in the mammalian and avian auditory hindbrain nuclei share a number of significant morphological and physiological properties for fast, secure and precise neurotransmission, such as giant synapses, voltage-gated K+ channels and fast AMPA receptors. Based on the independent evolution of the middle ear in these two vertebrate lineages, on different embryonic origins of the nuclei and on marked differences on the circuit level, these similarities are assumed to reflect convergent evolution. Independent acquisition of similar phenotypes can be produced by divergent evolution of genetic mechanisms or by similar molecular mechanisms. The distinction between these two possibilities requires knowledge of the gene regulatory networks (GRNs) that orchestrate the development of auditory hindbrain structures. We therefore compared the expression pattern of GRN components, both transcription factors (TFs) and noncoding RNA, during terminal differentiation of the auditory hindbrain structures in mouse and chicken when neurons acquire their final morphological and electrophysiological properties. In general, we observed broad expression of these genes in the mouse auditory cochlear nucleus complex and the superior olivary complex at both postnatal day 4 (P4) and at P25, and for the chicken at the equivalent developmental stages, i.e. embryonic day 13 (E13) and at P14-P17. Our data are in agreement with a model based on similar molecular mechanisms underlying terminal differentiation and maintenance of neuronal cell identity in the auditory hindbrain of different vertebrate lineages. This conservation might reflect developmental constraints arising from the tagmatic organization of rhombomeres and the evolutionarily highly conserved GRNs operating in these structures. Copyright © 2016 S. Karger AG, Basel. All rights reserved.

Raducu M.,Autonomous University of Madrid | Baets J.,Neurogenetics Group | Baets J.,University of Antwerp | Fano O.,Autonomous University of Madrid | And 2 more authors.
European Journal of Human Genetics | Year: 2012

Limb-girdle muscular dystrophy type 2O (LGMD2O) belongs to a group of rare muscular dystrophies named dystroglycanopathies, which are characterized molecularly by hypoglycosylation of α-dystroglycan (α-DG). Here, we describe the first dystroglycanopathy patient carrying an alteration in the promoter region of the POMGNT1 gene (protein O-mannose β-1,2-N- acetylglucosaminyltransferase 1), which involves a homozygous 9-bp duplication (-83-75dup). Analysis of the downstream effects of this mutation revealed a decrease in the expression of POMGNT1 mRNA and protein because of negative regulation of the POMGNT1 promoter by the transcription factor ZNF202 (zinc-finger protein 202). By functional analysis of various luciferase constructs, we localized a proximal POMGNT1 promoter and we found a 75% decrease in luciferase activity in the mutant construct when compared with the wild type. Electrophoretic mobility shift assay (EMSA) revealed binding sites for the Sp1, Ets1 and GATA transcription factors. Surprisingly, the mutation generated an additional ZNF202 binding site and this transcriptional repressor bound strongly to the mutant promoter while failing to recognize the wild-type promoter. Although the genetic causes of dystroglycanopathies are highly variable, they account for only 50% of the cases described. Our results emphasize the importance of extending the mutational screening outside the gene-coding region in dystroglycanopathy patients of unknown aetiology, because mutations in noncoding regions may be the cause of disease. Our findings also underline the requirement to perform functional studies that may assist the interpretation of the pathogenic potential of promoter alterations. © 2012 Macmillan Publishers Limited All rights reserved.

Mitchell J.,Neurogenetics Group | Paul P.,Neurogenetics Group | Chen H.-J.,Neurogenetics Group | Morris A.,Neurogenetics Group | And 12 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2010

We report a unique mutation in the D-amino acid oxidase gene (R199W DAO) associated with classical adult onset familial amyotrophic lateral sclerosis (FALS) in a three generational FALS kindred, after candidate gene screening in a 14.52 cM region on chromosome 12q22-23 linked to disease. Neuronal cell lines expressing R199W DAO showed decreased viability and increased ubiquitinated aggregates compared with cells expressing the wild-type protein. Similarly, lentiviral-mediated expression of R199WDAO in primary motor neuron cultures caused increased TUNEL labeling. This effect was also observed when motor neurons were cocultured on transduced astrocytes expressing R199W, indicating that the motor neuron cell death induced by this mutation is mediated by both cell autonomous and noncell autonomous processes. DAO controls the level of D-serine, which accumulates in the spinal cord in cases of sporadic ALS and in a mouse model of ALS, indicating that this abnormality may represent a fundamental component of ALS pathogenesis.

Mullen S.A.,University of Melbourne | Marini C.,University of Florence | Suls A.,Neurogenetics Group | Suls A.,Bunge | And 14 more authors.
Archives of Neurology | Year: 2011

Objective: To determine if a significant proportion of patients with myoclonic-astatic epilepsy (MAE) have glucose transporter 1 (GLUT1) deficiency. Design: Genetic analysis. Setting: Ambulatory and hospitalized care. Patients: Eighty-four unrelated probands with MAE were phenotyped and SLC2A1 was sequenced and analyzed by multiplex ligation-dependent probe amplification. Any identified mutations were then screened in controls. Main Outcome Measure: Any SLC2A1 mutations. Results: Four of 84 probands with MAE had a mutation of SLC2A1on sequencing. Multiplexligation-dependent probe amplification analysis didnot reveal any genomic rearrangements in 75 of the remaining cases; 5 could not be tested. Two patients with MAE with SLC2A1 mutations also developed paroxysmal exertional dyskinesia in childhood. Conclusions: Five percent of our patients with MAE had SLC2A1 mutations, suggesting that patients with MAE should be tested for GLUT1 deficiency. Diagnosis of GLUT1 deficiency is a strong indication for early use of the ketogenic diet, which may substantially improve outcome of this severe disorder. ©2011 American Medical Association. All rights reserved.

PubMed | University of Washington, Ambry Genetics, Copenhagen University, University of Kiel and 11 more.
Type: Journal Article | Journal: European journal of human genetics : EJHG | Year: 2016

Genetic generalized epilepsy (GGE), formerly known as idiopathic generalized epilepsy, is the most common form of epilepsy and is thought to have predominant genetic etiology. GGE are clinically characterized by absence, myoclonic, or generalized tonic-clonic seizures with electroencephalographic pattern of bilateral, synchronous, and symmetrical spike-and-wave discharges. Despite their strong heritability, the genetic basis of generalized epilepsies remains largely elusive. Nevertheless, recent advances in genetic technology have led to the identification of numerous genes and genomic defects in various types of epilepsies in the past few years. In the present study, we performed whole-exome sequencing in a family with GGE consistent with the diagnosis of eyelid myoclonia with absences. We found a nonsense variant (c.196C>T/p.(Arg66*)) in RORB, which encodes the beta retinoid-related orphan nuclear receptor (ROR), in four affected family members. In addition, two de novo variants (c.218T>C/p.(Leu73Pro); c.1249_1251delACG/p.(Thr417del)) were identified in sporadic patients by trio-based exome sequencing. We also found two de novo deletions in patients with behavioral and cognitive impairment and epilepsy: a 52-kb microdeletion involving exons 5-10 of RORB and a larger 9q21-microdeletion. Furthermore, we identified a patient with intellectual disability and a balanced translocation where one breakpoint truncates RORB and refined the phenotype of a recently reported patient with RORB deletion. Our data support the role of RORB gene variants/CNVs in neurodevelopmental disorders including epilepsy, and especially in generalized epilepsies with predominant absence seizures.

Weckhuysen S.,Neurogenetics Group | Weckhuysen S.,University of Antwerp | Korff C.M.,University of Geneva
Current Neurology and Neuroscience Reports | Year: 2014

Next-generation sequencing technologies have tremendously increased the speed of gene discovery in monogenic epilepsies, enabling us to identify a genetic cause in an increasing proportion of patients, and to better understand the underlying pathophysiology of their disease. The rapid speed with which new genes are being described lately, confronts clinicians with the difficult task of keeping up to date with the continuous supply of new publications. This article aims to discuss some of the genes that were recently discovered in monogenic familial epilepsy syndromes or epileptic encephalopathies for which an underlying cause remained unknown for a long time. © 2014 Springer Science+Business Media.

PubMed | University Hospitals Leuven, Neurogenetics Group and Bunge
Type: Journal Article | Journal: Acta neurologica Belgica | Year: 2016

Mutations in POLG are increasingly recognized as a cause of refractory occipital lobe epilepsy (OLE) and status epilepticus (SE). Our aim was to describe the epilepsy syndrome in seven patients with POLG mutations. We retrospectively reviewed the medical records of seven patients with POLG mutations and epilepsy. Mutation analysis was performed by direct sequencing of the coding exons of the POLG gene. Disease onset was at a median age of 18 years (range 12-26). Epilepsy was the presenting problem in six patients. All had focal seizures, with motor (n = 6) and visual (n = 6) phenomena. Six patients had secondarily generalized seizures and two patients had myoclonic seizures. Six patients had one or more episodes of refractory SE, including focal (n = 5), subtle (n = 4), myoclonic (n = 2) and convulsive (n = 3) SE. During or after SE, brain MRI showed lesions affecting the occipital lobe in all patients, probably due to continuous epileptic activity. Five of the six patients with SE died during treatment of SE, one due to valproate-induced hepatotoxicity. Associated clinical symptoms were ataxia (n = 6), polyneuropathy (n = 6), progressive external ophthalmoplegia (PEO) (n = 3) and migraine (n = 3). Epilepsy may be the first and dominant neurological problem caused by POLG mutations. The epilepsy may be severe and the condition of the patient may end in fatal SE. Refractory OLE and SE in a patient with polyneuropathy, ataxia, PEO or migraine warrant screening for POLG mutations. In this clinical setting, valproate should not be given in view of the risk of fatal hepatotoxicity.

Mullen S.A.,University of Melbourne | Suls A.,Neurogenetics Group | Suls A.,Bunge | Suls A.,University of Antwerp | And 6 more authors.
Neurology | Year: 2010

Background: Familial glucose transporter type 1 (GLUT1) deficiency due to autosomal dominant inheritance of SLC2A1 mutations is associated with paroxysmal exertional dyskinesia; epilepsy and intellectual disability occur in some family members. We recently demonstrated that GLUT1 deficiency occurs in over 10% of patients with early-onset absence epilepsy. Methods: This family study analyses the phenotypes in 2 kindreds segregating SLC2A1 mutations identified through probands with early-onset absence epilepsy. One comprised 9 individuals with mutations over 3 generations; the other had 6 individuals over 2 generations. Results: Of 15 subjects with SLC2A1 mutations, epilepsy occurred in 12. Absence seizures were the most prevalent seizure type (10/12), with onset from 3 to 34 years of age. Epilepsy phenotypes varied widely, including idiopathic generalized epilepsies (IGE) with absence (8/12), myoclonic-astatic epilepsy (2/12), and focal epilepsy (2/12). Paroxysmal exertional dyskinesia occurred in 7, and was subtle and universally undiagnosed prior to molecular diagnosis. There were 2 unaffected mutation carriers. Conclusions: GLUT1 deficiency is an important monogenic cause of absence epilepsies with onset from early childhood to adult life. Individual cases may be phenotypically indistinguishable from common forms of IGE. Although subtle paroxysmal exertional dyskinesia is a helpful diagnostic clue, it is far from universal. The phenotypic spectrum of GLUT1 deficiency is considerably greater than previously recognized. Diagnosis of GLUT1 deficiency has important treatment and genetic counseling implications. © 2010 by AAN Enterprises, Inc.

Bandopadhyay R.,University College London | de Belleroche J.,Neurogenetics Group
Trends in Molecular Medicine | Year: 2010

Several neurodegenerative diseases, including Parkinson's disease (PD) are associated with protein misfolding and the formation of distinct aggregates, resulting in a putative pathological protein load on the nervous system. A variety of factors cause proteins to aggregate, including aggregation-prone sequences, specific mutations, protein modifications and also dysregulation of the protein degradation machinery. Molecular chaperones are responsible for maintaining normal protein homeostasis within the cell by assisting protein folding and modulating protein-degrading pathways. Here, we review the fundamental mechanisms of neurodegeneration occurring in PD involving α-synuclein fibrillisation and aggregation, endoplasmic reticulum stress, ubiquitin proteasome systems, autophagy and lysosomal degradation. Molecular chaperones serve a neuroprotective role in many of these pathways, and we discuss recent evidence indicating that these proteins might provide the basis for new therapeutic approaches. © 2009 Elsevier Ltd. All rights reserved.

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