Absence ofGABRA1 Ala322Asp mutation in juvenile myoclonic epilepsy families from India

Novel variants in GABAA receptor subunits: A possible association with benzodiazepine resistance in patients with drug-resistant epilepsy

Benzodiazepines (BDZ) such as diazepam and lorazepam are popular as first-line treatment for acute seizures due to their rapid action and high efficacy. However, long-term usage of BDZ leads to benzodiazepine resistance, a phenomenon whose underlying mechanisms are still being investigated. One of the hypothesised mechanisms contributing to BDZ resistance is the presence of mutations in benzodiazepine-sensitive receptors. While a few genetic variants have been reported previously, knowledge of relevant pathogenic variants is still scarce. We used Sanger Sequencing to detect variants in the ligand-binding domain of BDZ-sensitive GABA_A receptor subunits α1-3 and 5 expressed in resected brain tissues of drug-resistant epilepsy (DRE) patients with a history of BDZ resistance and found two previously unreported predicted pathogenic frameshifting variants - NM_000807.4(GABRA2):c.367_368insG and NM_000810.4(GABRA5):c.410del - significantly enriched in these patients. The findings were further explored in resected DRE brain tissues through cellular electrophysiological experiments.

Association of GABAA Receptor Gene with Epilepsy Syndromes

GABA has always been an inviting target in the etiology and treatment of epilepsy. The GABRA1, GABRG2, and GABRD genes provide instructions for making α1, ϒ2, and δ subunits of GABAA receptor protein respectively. GABAA is considered as one of the most important proteins and has found to play an important role in many neurological disorders. We explored the association of GABAA receptor gene mutation/SNPs in JME and LGS patients in Indian population. A total of 100 epilepsy syndrome patients (50 JME and 50 LGS) and 100 healthy control subjects were recruited and analyzed by AS-PCR and RFLP-PCR techniques. In our study, GABRA1 965 C > A mutation and 15 A > G polymorphism gene may play an important role in modulating the drug efficacy in LGS patients. The GABRA1 15 A > G polymorphism may also play an important role in the susceptibility of LGS and the inheritance of GG genotype of this polymorphism may provide an increased risk of development of LGS. The GABRG2 588 C > T polymorphism may decrease the duration of seizures in JME patients. The GABRD 659 G > A polymorphism may play an important role in the susceptibility of JME and LGS and this polymorphism may also increase the duration of postictal period in JME patients but may decrease the duration of seizure in LGS patients.

Molecular Genetics of Epilepsy: A Clinician's Perspective

Epilepsy is a common neurological problem, and there is a genetic basis in almost 50% of people with epilepsy. The diagnosis of genetic epilepsies makes the patient assured of the reasons of his/her seizures and avoids unnecessary, expensive, and invasive investigations. Last decade has shown tremendous growth in gene sequencing technologies, which have made genetic tests available at the bedside. Whole exome sequencing is now being routinely used in the clinical setting for making a genetic diagnosis. Genetic testing not only makes the diagnosis but also has an effect on the management of the patients, for example, the role of sodium channels blockers in SCN1A+ Dravet syndrome patients and usefulness of ketogenic diet therapy in SLC2A1+ generalized epilepsy patients. Many clinicians in our country have no or limited knowledge about the molecular genetics of epilepsies, types of genetic tests available, how to access them and how to interpret the results. The purpose of this review is to give an overview in this direction and encourage the clinicians to start considering genetic testing as an important investigation along with electroencephalogram and magnetic resonance imaging for better understanding and management of epilepsy in their patients.

Epilepsy: Indian perspective

There are 50 million people living with epilepsy worldwide, and most of them reside in developing countries. About 10 million persons with epilepsy are there in India. Many people with active epilepsy do not receive appropriate treatment for their condition, leading to large treatment gap. The lack of knowledge of antiepileptic drugs, poverty, cultural beliefs, stigma, poor health infrastructure, and shortage of trained professionals contribute for the treatment gap. Infectious diseases play an important role in seizures and long-term burden causing both new-onset epilepsy and status epilepticus. Proper education and appropriate health care services can make tremendous change in a country like India. There have been many original researches in various aspects of epilepsy across India. Some of the geographically specific epilepsies occur only in certain regions of our country which have been highlighted by authors. Even the pre-surgical evaluation and epilepsy surgery in patients with drug-resistant epilepsy is available in many centers in our country. This article attempts to provide a complete preview of epilepsy in India.

Genetic polymorphisms and idiopathic generalized epilepsies

In recent years, progress in understanding the genetic basis of idiopathic generalized epilepsies has proven challenging because of their complex inheritance patterns and genetic heterogeneity. Genetic polymorphisms offer a convenient avenue for a better understanding of the genetic basis of idiopathic generalized epilepsy by providing evidence for the involvement of a given gene in these disorders, and by clarifying its pathogenetic mechanisms. Many of these genes encode for some important central nervous system ion channels (KCNJ10, KCNJ3, KCNQ2/KCNQ3, CLCN2, GABRG2, GABRA1, SCN1B, and SCN1A), while many others encode for ubiquitary enzymes that play crucial roles in various metabolic pathways (HP, ACP1, ME2, LGI4, OPRM1, GRIK1, BRD2, EFHC1, and EFHC2). We review the main genetic polymorphisms reported in idiopathic generalized epilepsy, and discusses their possible functional significance in the pathogenesis of seizures.

Adult-onset autosomal dominant myoclonic epilepsy: Report of a family with an overlooked epileptic syndrome

OBJECTIVE

Myoclonic epilepsy is a common epileptic syndrome with high genetic contribution. We described a pedigree in which 10 individuals presented with a non-progressive, adult-onset myoclonic epilepsy.

MATERIALS AND METHODS

The pedigree was constructed and analyzed. Six affected members were studied with clinical grounds, mental status, neurophysiology, video-electroencephalographic (EEG), brain magnetic resonance imaging (MRI) and mutational analysis of GABRA1 (GABRA1A, which endoces the alpha1 subunit of the gamma-aminobutyric acid receptor subtype A). Clinical and EEG data were collected from six unaffected members.

RESULTS

Autosomal dominant hereditary was shown. The age of seizure onset was approximately 40. All the individuals had myoclonic seizures and a normal cognitive level. Bilateral symmetric jerks of the shoulders, arms or legs featured the myoclonic seizure. Ictally, the consciousness was not affected. The ictal EEG demonstrated bilateral spikes-and-waves. The occurrence of myoclonic seizures was not associated with sleepiness. Rare generalized tonic-clonic seizures occurred in two individuals. No absence or accompanying involuntary movements were observed. A lower dose of valproic acid (200-500 mg/D) (clonazepam 0.5 mg/D in a patient) was required to stop the myoclonic seizures.

CONCLUSIONS

The clinical features of late adult-onset autosomal dominant myoclonic epilepsy are similar to juvenile myoclonic epilepsy (JME), which is a common generalized epileptic syndrome with a significant hereditary component. But the age of onset, rare association of other seizure patterns, and non-relation of seizure onset to sleepiness suggest that this may be a distinct familial epileptic syndrome different from recognized familial myoclonic epilepsies.

Observations on juvenile myoclonic epilepsy amongst ethnic Bengalees in West Bengal—An Eastern Indian State

BACKGROUND

Juvenile myoclonic epilepsy (JME) is not too uncommonly encountered in Indian neurological practice. A number of reports from different parts of India have documented the clinical phenomenology and EEG characteristics of this genetically determined epileptic syndrome. However, no study has yet been reported from the Eastern part of India and none done so far in patients in a specific ethnic group. Furthermore therapy response and follow up data are not available in detail in the Indian studies.

OBJECTIVE

To study disease expression, EEG characteristics and therapy response of JME patients in ethnic Bengalees in West Bengal, an Eastern Indian State, in a clinic based study.

MATERIAL AND METHODS

200 patients with JME attending the Neurology Department of the Institute have been followed up for 5 years and different parameters of disease expression as outlined above have been studied.

RESULTS

Overall clinical disease expression has been found to be similar in this clinic based study in ethnic Bengalees as compared to other reports from India and elsewhere. About 16% of patients showed a relative resistance to Valproate therapy. Hundred percent of patients in whom therapy withdrawal was attempted, relapsed within<1-2 years. Amongst female patients (132), 16 developed features of polycystic ovarian syndrome while on Valproate therapy. In over half of them, the symptoms regressed after successful switch over from Valproate to Clobazam. 12/132 female patients became pregnant during follow up and while on Valproate; teratogenic effect was evident in only one such patient.

CONCLUSIONS

Phenotypic variations in disease expression including therapy response have been noted within a single ethnic group of patients attending the clinic and might account for genetic heterogeneity noted in molecular genetic studies. JME cannot really be called a very 'benign' epileptic syndrome; recurrence after therapy withdrawal almost invariably occurs.

Mutations in the GABRA1 and EFHC1 genes are rare in familial juvenile myoclonic epilepsy

Juvenile myoclonic epilepsy (JME), accounting for approximately 25% of idiopathic generalized epilepsies, is genetically heterogeneous. Mutations in the alpha-1 subunit of the GABAA receptor (GABRA1) and EFHC1 genes have been reported in a few families with autosomal dominant (AD) JME. We have investigated the contribution of these two genes to familial JME in our cohort of 54 JME Caucasian families. Syndromic classification of JME was based on previously published criteria. We considered kindreds with at least one affected first-degree relative and the evidence of a vertical transmission as definite AD JME, and families with at least one affected second-degree relative as probable AD JME. We included 33 families meeting criteria for definitive AD JME and 21 that were classified as probable AD JME. None of these families were considered informative enough to analyze candidate loci for JME using linkage analysis. We have systematically screened coding exons of these two genes using temperature gradient capillary electrophoresis. Every heteroduplex with an abnormal mobility was sequenced. No disease-causing mutations in the GABRA1 gene were identified. Analysis of EFHC1 gene found one putative disease-causing mutation R221H that was previously reported as a tandem mutation. Several synonymous and non-synonymous coding polymorphisms were identified but the allelic frequency did not differ between controls and affected individuals. Our data suggests that the majority of familial AD JME is not caused by mutations in the GABRA1 and EFHC1 genes.

Mechanisms, genetics, and pathogenesis of juvenile myoclonic epilepsy: review

PURPOSE OF REVIEW

This review addresses the mechanisms, genetics and pathogenesis of juvenile myoclonic epilepsy (JME, Janz syndrome).

RECENT FINDINGS

Although JME is a well defined clinical syndrome among the idiopathic generalized epilepsies (IGEs), recent studies suggest that JME is distinct from other IGE syndromes and must be considered separately for the purposes of genetic studies. Clinical, morphological and metabolic data suggest a preferential role for frontal regions in this syndrome. However, JME is clinically and genetically heterogeneous. Although several major genes for JME have been identified and pathogenetic mechanisms suggested based on these findings, these genes account for only a small proportion of JME cases, suggesting multifactorial or complex inheritance in most. The roles played by other major genes, susceptibility genes and environmental factors in the pathogenesis of JME remain to be defined.

SUMMARY

JME is clinically and genetically heterogeneous and should be considered separately from other IGE syndromes. Proposed mechanisms, such as those involving microdysgenesis or altered neuronal inhibition, may be related to different genetic abnormalities in different patients. Major genes account for relatively few cases, and most cases appear to involve multifactorial or complex inheritance.