Ultra-rare genetic variation in common epilepsies: a case-control sequencing study

WITHDRAWN: Genetics update: Monogenetics, polygene disorders and the quest for modifying genes

The Publisher regrets that this article is an accidental duplication of an article that has already been published, https://doi.org/10.1016/j.neuropharm.2017.10.013. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal.

ExACtly zero or once: A clinically helpful guide to assessing genetic variants in mild epilepsies

Objective:

To assist the interpretation of genomic data for common epilepsies, we asked whether variants implicated in mild epilepsies in autosomal dominant families are present in the general population.

Methods:

We studied 12 genes for the milder epilepsies and identified published variants with strong segregation support (de novo germline mutation or ≥4 affected family members). These variants were checked in the Exome Aggregation Consortium (ExAC), a database of genetic variation in over 60,000 individuals. We subsequently evaluated variants in these epilepsy genes that lacked strong segregation support. To determine whether the findings in epilepsies were representative of other diseases, we also assessed the presence of variants in other dominant neurologic disorders (e.g., CADASIL).

Results:

Published epilepsy variants with strong segregation support (n = 65) were absent (n = 61) or present once (n = 4) in ExAC. By contrast, of 46 published epilepsy variants without strong segregation support, 8 occurred recurrently (2–186 times). Similarly, none of the 45 disease-associated variants from other neurologic disorders with strong segregation support occurred more than once in ExAC. Reanalysis using the larger ExAC V2 plus gnomAD reference cohort showed consistent results.

Conclusions:

Variants causing autosomal dominant epilepsies are ultra-rare in the general population. Variants observed more than once in ExAC were only found among reports without strong segregation support, suggesting that they may be benign. Clinicians are increasingly faced with the interpretation of genetic variants of unknown significance. These data illustrate that variants present more than once in ExAC are less likely to be pathogenic, reinforcing the valuable clinical role of ExAC.

Optogenetic Approaches to Drug Discovery in Neuroscience and Beyond

Recent advances in optogenetics have opened new routes to drug discovery, particularly in neuroscience. Physiological cellular assays probe functional phenotypes that connect genomic data to patient health. Optogenetic tools, in particular tools for all-optical electrophysiology, now provide a means to probe cellular disease models with unprecedented throughput and information content. These techniques promise to identify functional phenotypes associated with disease states and to identify compounds that improve cellular function regardless of whether the compound acts directly on a target or through a bypass mechanism. This review discusses opportunities and unresolved challenges in applying optogenetic techniques throughout the discovery pipeline - from target identification and validation, to target-based and phenotypic screens, to clinical trials.

Genetic Testing in Pediatric Epilepsy

PURPOSE OF REVIEW

This article summarizes the emerging landscape of pediatric epilepsy, highlighting genetic contributions, and reviews approaches to genetic evaluation for pediatric epilepsy in this context.

RECENT FINDINGS

Advances in understanding the genetic basis for epilepsy over the last several years have been due in large part to the identification of de novo genetic variation underlying sporadic severe epilepsy in children; the genetic underpinnings of the more common epilepsies remain largely unknown. Next-generation sequencing approaches have been added to the repertoire of clinical tests for the evaluation of pediatric epilepsy, improving our ability to make positive diagnoses. Yields of over 50% are now being reported in selected groups of patients. Genetic variation contributing to the risk for pediatric epilepsy spans continua of scale and influence. The highest yield of genetic testing is currently in children with sporadic severe epilepsy caused by de novo variation. The approach to genetic evaluation and interpretation of results requires an understanding of (1) the epilepsy phenotype and (2) the particular advantages and limitations of the different genetic tests available. Our understanding of genetic variation will continue to improve over time and "negative" results are best conceptualized as "unresolved" or "negative for now."

The impact of genetic and experimental studies on classification and therapy of the epilepsies

Different types of epilepsy are associated with gene mutations, in which seizures can be the only symptom (genetic epilepsies) or be one of the elements of complex clinical pictures that are often progressive over time (epileptic or epileptogenic encephalopathies). In epileptogenic encephalopathies, epileptic seizures and other neurological and cognitive signs are symptoms of genetically determined neuropathological or neurochemical disorders. In epileptic encephalopathies, epileptic activity itself is thought to contribute to severe cognitive and behavioral impairments above and beyond what might be expected from the underlying pathology alone. The distinction is conceptually clear and clinically relevant, as the different categories have a different prognosis in terms of both epilepsy and associated neurological and cognitive picture, but the boundaries are sometimes difficult to define in the clinical practice. Here we review the genetic epilepsies from the clinician perspective. A monogenic inheritance has been defined only in a minority of idiopathic epilepsies making improper to rename genetic the category of idiopathic epilepsies, until the presumptive multigenic mechanism will be demonstrated. A search for gene mutations must be done in any patient with candidate genetic types of epilepsy or epileptic/epileptogenic encephalopathy (e.g. familial forms) to complete the diagnostic process, define the prognosis and optimize the therapy. Advanced methods are available to express the gene variant in experimental model systems and test its effect on the properties of the affected protein, on neuronal excitability and on phenotypes in model organisms, and may help in identifying treatments with compatible action mechanisms. The influence of genetic studies on epilepsy taxonomy is now a matter of discussion: their impact on the international classification of the epilepsies will hopefully be defined soon.