Mice Doubly-Deficient in Lysosomal Hexosaminidase A and Neuraminidase 4 Show Epileptic Crises and Rapid Neuronal Loss

Tay-Sachs disease is a severe lysosomal disorder caused by mutations in the HexA gene coding for the α-subunit of lysosomal β-hexosaminidase A, which converts GM2 to GM3 ganglioside. Hexa−/− mice, depleted of β-hexosaminidase A, remain asymptomatic to 1 year of age, because they catabolise GM2 ganglioside via a lysosomal sialidase into glycolipid GA2, which is further processed by β-hexosaminidase B to lactosyl-ceramide, thereby bypassing the β-hexosaminidase A defect. Since this bypass is not effective in humans, infantile Tay-Sachs disease is fatal in the first years of life. Previously, we identified a novel ganglioside metabolizing sialidase, Neu4, abundantly expressed in mouse brain neurons. Now we demonstrate that mice with targeted disruption of both Neu4 and Hexa genes (Neu4−/−;Hexa−/−) show epileptic seizures with 40% penetrance correlating with polyspike discharges on the cortical electrodes of the electroencephalogram. Single knockout Hexa−/− or Neu4−/− siblings do not show such symptoms. Further, double-knockout but not single-knockout mice have multiple degenerating neurons in the cortex and hippocampus and multiple layers of cortical neurons accumulating GM2 ganglioside. Together, our data suggest that the Neu4 block exacerbates the disease in Hexa−/− mice, indicating that Neu4 is a modifier gene in the mouse model of Tay-Sachs disease, reducing the disease severity through the metabolic bypass. However, while disease severity in the double mutant is increased, it is not profound suggesting that Neu4 is not the only sialidase contributing to the metabolic bypass in Hexa−/− mice

Rare coding variants in genes encoding GABA_A receptors in genetic generalised epilepsies: an exome-based case-control study

BACKGROUND: Genetic generalised epilepsy is the most common type of inherited epilepsy. Despite a high concordance rate of 80% in monozygotic twins, the genetic background is still poorly understood. We aimed to investigate the burden of rare genetic variants in genetic generalised epilepsy. METHODS: For this exome-based case-control study, we used three different genetic generalised epilepsy case cohorts and three independent control cohorts, all of European descent. Cases included in the study were clinically evaluated for genetic generalised epilepsy. Whole-exome sequencing was done for the discovery case cohort, a validation case cohort, and two independent control cohorts. The replication case cohort underwent targeted next-generation sequencing of the 19 known genes encoding subunits of GABAA receptors and was compared to the respective GABAA receptor variants of a third independent control cohort. Functional investigations were done with automated two-microelectrode voltage clamping in Xenopus laevis oocytes. FINDINGS: Statistical comparison of 152 familial index cases with genetic generalised epilepsy in the discovery cohort to 549 ethnically matched controls suggested an enrichment of rare missense (Nonsyn) variants in the ensemble of 19 genes encoding GABAA receptors in cases (odds ratio [OR] 2·40 [95% CI 1·41-4·10]; pNonsyn=0·0014, adjusted pNonsyn=0·019). Enrichment for these genes was validated in a whole-exome sequencing cohort of 357 sporadic and familial genetic generalised epilepsy cases and 1485 independent controls (OR 1·46 [95% CI 1·05-2·03]; pNonsyn=0·0081, adjusted pNonsyn=0·016). Comparison of genes encoding GABAA receptors in the independent replication cohort of 583 familial and sporadic genetic generalised epilepsy index cases, based on candidate-gene panel sequencing, with a third independent control cohort of 635 controls confirmed the overall enrichment of rare missense variants for 15 GABAA receptor genes in cases compared with controls (OR 1·46 [95% CI 1·02-2·08]; pNonsyn=0·013, adjusted pNonsyn=0·027). Functional studies for two selected genes (GABRB2 and GABRA5) showed significant loss-of-function effects with reduced current amplitudes in four of seven tested variants compared with wild-type receptors. INTERPRETATION: Functionally relevant variants in genes encoding GABAA receptor subunits constitute a significant risk factor for genetic generalised epilepsy. Examination of the role of specific gene groups and pathways can disentangle the complex genetic architecture of genetic generalised epilepsy. FUNDING: EuroEPINOMICS (European Science Foundation through national funding organisations), Epicure and EpiPGX (Sixth Framework Programme and Seventh Framework Programme of the European Commission), Research Unit FOR2715 (German Research Foundation and Luxembourg National Research Fund)

Rare coding variants in genes encoding GABA(A) receptors in genetic generalised epilepsies : an exome-based case-control study

Background Genetic generalised epilepsy is the most common type of inherited epilepsy. Despite a high concordance rate of 80% in monozygotic twins, the genetic background is still poorly understood. We aimed to investigate the burden of rare genetic variants in genetic generalised epilepsy. Methods For this exome-based case-control study, we used three different genetic generalised epilepsy case cohorts and three independent control cohorts, all of European descent. Cases included in the study were clinically evaluated for genetic generalised epilepsy. Whole-exome sequencing was done for the discovery case cohort, a validation case cohort, and two independent control cohorts. The replication case cohort underwent targeted next-generation sequencing of the 19 known genes encoding subunits of GABA(A) receptors and was compared to the respective GABA(A) receptor variants of a third independent control cohort. Functional investigations were done with automated two-microelectrode voltage clamping in Xenopus laevis oocytes. Findings Statistical comparison of 152 familial index cases with genetic generalised epilepsy in the discovery cohort to 549 ethnically matched controls suggested an enrichment of rare missense (Nonsyn) variants in the ensemble of 19 genes encoding GABA(A) receptors in cases (odds ratio [OR] 2.40 [95% CI 1.41-4.10]; p(Nonsyn)=0.0014, adjusted p(Nonsyn)=0.019). Enrichment for these genes was validated in a whole-exome sequencing cohort of 357 sporadic and familial genetic generalised epilepsy cases and 1485 independent controls (OR 1.46 [95% CI 1.05-2.03]; p(Nonsyn)=0.0081, adjusted p(Nonsyn)=0.016). Comparison of genes encoding GABA(A) receptors in the independent replication cohort of 583 familial and sporadic genetic generalised epilepsy index cases, based on candidate-gene panel sequencing, with a third independent control cohort of 635 controls confirmed the overall enrichment of rare missense variants for 15 GABA(A) receptor genes in cases compared with controls (OR 1.46 [95% CI 1.02-2.08]; p(Nonsyn)=0.013, adjusted p(Nonsyn)=0.027). Functional studies for two selected genes (GABRB2 and GABRA5) showed significant loss-of-function effects with reduced current amplitudes in four of seven tested variants compared with wild-type receptors. Interpretation Functionally relevant variants in genes encoding GABA(A) receptor subunits constitute a significant risk factor for genetic generalised epilepsy. Examination of the role of specific gene groups and pathways can disentangle the complex genetic architecture of genetic generalised epilepsy. Copyright (C) 2018 The Author(s). Published by Elsevier Ltd.Peer reviewe

Automatisation d'un alambique charentais

9 graph. Numéro spécial : AutomatiqueNational audienc

Non-Invasive Pre-Surgical Investigation of a 10 Year-Old Epileptic Boy Using Simultaneous Eeg-Nirs

SummaryNear-infrared spectroscopy (NIRS) is a novel imaging technique of potential value in the pre-surgical investigation of patients with refractory epilepsy. We recorded simultaneously electrophysiology (EEG; Compumedics, USA) and near-infrared spectroscopy (NIRS; ISS, USA) to examine the localization of the ictal onset zone and assess language lateralization in a young epileptic boy (L.H., 10 years) as part of his pre-surgical evaluation. L.H. underwent a prolonged EEG–NIRS recording while electro-clinical and electrical seizures were recorded. Results were compared to those obtained with other pre-surgical techniques (SPECT, FDG–PET, EEG–fMRI and EEG–MEG) and showed good concordance for ictal onset zone localization. A second NIRS session without EEG was carried out in order to investigate language lateralization. For this purpose, the patient performed a categorical verbal-fluency task during NIRS recordings. Results showed left-hemisphere dominance for language function in this young boy. This case report illustrates that multi-channel EEG–NIRS has the potential to contribute favourably to pre-surgical investigation in young patients

TLR3 preconditioning induces anti-inflammatory and anti-ictogenic effects in mice mediated by the IRF3/IFN-β axis

Activation of Toll-like receptor 3 (TLR3) was previously shown to contribute to the generation of epileptic seizures in rodents by evoking a proinflammatory response in the forebrain. This suggests that TLR3 blockade may provide therapeutic effects in epilepsy. We report that brain activation of TLR3 using the synthetic receptor ligand Poly I:C may also result in remarkable dose- and time-dependent inhibitory effects on acute seizures in mice without inducing inflammation. These inhibitory effects are associated with reduced neuronal excitability in the hippocampus as shown by a decrease in the population spike amplitude of CA1 pyramidal neurons following Schaffer collaterals stimulation. TLR3 activation which results in seizure inhibition does not evoke NF-kB-dependent inflammatory molecules or morphological activation of glia, however, it induces the alternative interferon (IFN) regulatory factor (IRF)-3/IFN-β signaling pathway. IFN-β reproduced the inhibitory effects of Poly I:C on neuronal excitability in hippocampal slices. Seizure inhibition attained with activation the TLR3-IRF3/IFN-β axis should be carefully considered when TLR3 are targeted for therapeutic purposes

Spectroscopic Metabolic Abnormalities in mTLE with and without MRI Evidence for Mesial Temporal Sclerosis Using Hippocampal Short-TE MRSI

PURPOSE: Long echo time (TE) spectroscopy reliably identifies the epileptogenic hippocampus in mesial temporal lobe epilepsy. Short-TE spectroscopy gives additional metabolic information but may have more artifacts. The aim of this study was to test (a) lateralization of the seizure focus by short-TE spectroscopy, and (b) value of myoinositol (MI) in the identification of the epileptogenic hippocampus. METHODS: Twenty-four patients with temporal lobe epilepsy: 16 with mesial temporal sclerosis (TLE-MTS), eight patients with normal magnetic resonance imaging (MRI; TLE-No), and 16 controls were studied with hippocampal 2D short-TE magnetic resonance spectroscopic imaging (MRSI). RESULTS: In TLE-MTS, the ipsilateral N-acetylaspartate (NAA) was decreased compared with contralateral (p = 0.03) or controls (p = 0.007). Additionally, the ipsilateral MI was decreased compared with controls (p = 0.012). TLE-No values showed no side differences and were not different from controls. Abnormalities in the anterior hippocampus correctly lateralized the epileptogenic hippocampus in ≤82% of TLE-MTS and in ≤80% of the TLE-No. CONCLUSIONS: The accuracy of short-TE MRSI at 1.5 T for focus lateralization in mTLE is comparable to that of long-TE MRSI. MI might be helpful for focus lateralization, but more information about the factors influencing the MI concentration is needed