SCN1A gain-of-function, paralogs, and the Philadelphia variant

Between the ion channels. Rather than going “beyond the ion channel,” in this post, we aim to look between them. We want to dive into a study where examining the group of epilepsy-related sodium channels was initially more informative than the single gene itself—even when that gene was SCN1A, the most established epilepsy gene. A recurrent SCN1A variant turned out to be part of an emerging, previously underappreciated gain-of-function spectrum. Here, we discuss the unusual phenotype of SCN1A gain-of-function variants and how we are currently working on integrating information on paralogs into the official ACMG variant curation criteria.

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The new genetics of Dravet Syndrome

Sundance. I was asked to give a talk on the genetics of Dravet Syndrome at the Dravet Syndrome Foundation meeting in Fort Worth, Texas. I started my presentation asking the question whether there is actually anything novel to talk about given that it is well established that Dravet Syndrome is due to loss-of-function variants in SCN1A, and the challenges are in finding better treatments, not in refining SCN1A genetics. However, this is not quite true. There are several new aspects regarding the genetics of Dravet Syndrome that are worth highlighting. Continue reading

This was AES 2021 – five takeaways from Chicago

Pandemic. This year’s Annual Meeting of the American Epilepsy Society (AES) was the 75th meeting, but it was a meeting like no other. #AES2021 was the first in-person meeting for the international epilepsy community with many international participants unable to join due to local restrictions and the US-based audience split between participating in-person and joining remotely. However, despite the unusual format, this year’s meeting was bustling and full of excellent science. Here are my five takeaways from AES 2021. Continue reading

AES 2018 Recap: The Epilepsy Community Invades the Big Easy

NOLA.The American Epilepsy Society (AES) has wrapped up its annual meeting, which was held this year in New Orleans. AES is the largest meeting of epilepsy professionals working in clinical practice, academia, industry, and advocacy. It is a meeting I always look forward to as an opportunity to connect with friends and colleagues from across the world. As we all pack away our beads and digest our beignets, I would like to reflect on some of the major messages I, as an epilepsy genetics clinician and researcher, took away from this year’s AES annual meeting. Continue reading

SCN1A-related epileptic encephalopathy: Beyond Dravet syndrome

SCN1A phenotypes. Readers of Beyond the Ion Channel will know that we often post about SCN1A, one of the first discovered and most common genetic causes of epileptic encephalopathy. We more or less assume that we understand the phenotypes associated with pathogenic variants in SCN1A: most commonly Dravet syndrome, which is associated with de novo variants, and less commonly genetic epilepsy with febrile seizures plus (GEFS+), associated with inherited missense variants. However, a recent publication by Sadleir and colleagues suggests that the phenotypic spectrum of SCN1A-related disorders may be broader than we have previously appreciated. Are there SCN1A-related epileptic encephalopathies in addition to Dravet syndrome? Continue reading

The story of the missed SCN1A mutations

Dravet Syndrome. In 2011, our EuroEPINOMICS-RES program was in full swing. We had recruited a cohort of 31 patients with Dravet Syndrome who had been previously tested negative for mutations in SCN1A with the aim to identify novel genes for this epileptic encephalopathy. Even though this cohort was crucial in our identification of CHD2, HCN1, and KCNA2 as novel genes for genetic epilepsies, the main finding in this cohort was something that we did not expect. Roughly one third of our 31 patients had mutations in SCN1A, even though they had previously been tested negative. In a recent publication in Molecular Genetics and Genomic Medicine, we tried to understand what had happened and joined forces with other groups who had made the same observation. Here is the story of the missed SCN1A mutations. Continue reading

Mysteries of a neuronal pathfinder – this is what you should know about PCDH19 in 2015

Protocadherin. There are some genes that we have mentioned less frequently on our blog than we should have. PCDH19 and CDKL5 are two examples of this. With this post, we try to catch up by reviewing some of the new findings related to PCDH19 Female Epilepsy including the role of neurosteroids, anti-NMDA receptor antibodies, stiripentol and the mechanism behind this epilepsy. Continue reading

Publications of the week – Dravet Syndrome, TBC1D24, and CSTB

Issue 6/2015. Publications from the most recent issue of Epilepsia are very prominent in this week’s selection of publications. We discuss the frequency of Dravet Syndrome, a novel family with a TBC1D24 mutation, and the role of Cystatin B (CSTB) in Juvenile Myoclonic Epilepsy. Continue reading

Flickering lights, endophenotypes, and EEG genetics – CHD2 in photosensitivity

Heritable. Many epilepsy syndromes have signature EEG traits, and these traits are thought to have a strong genetic component. The endophenotype concept suggests that using these epilepsy-related traits in genetic studies will facilitate gene discovery, a concept that has failed us so far in epilepsy research, unfortunately. Now, in a recent publication in Brain, we were able to demonstrate that variants in CHD2 predispose to photosensitivity, an abnormal cortical response to flickering light. Finally, after several decades of persisting difficulties, there is some progress in the field of EEG genetics. Continue reading

The two faces of KCNA2 – a novel epileptic encephalopathy

Delayed rectifier. The discovery of de novo mutations in ion channel genes as a cause for genetic epilepsies continues. In a recent publication in Nature Genetics, we have identified de novo mutations in KCNA2 as a novel cause of epileptic encephalopathies associated with ataxia. Interestingly, even within a single gene, two different phenotypes seem to be emerging. Continue reading