A long-awaited answer. Gene discovery in the epilepsies is continuing, and some novel genetic etiologies are quite surprising given that the particular genes had previously been described in a completely different context. One of these examples is TRPM3. In our recent publication, we further define TRPM3 as a gene causative of a variety of neurodevelopmental disorders. Also notably, we find that the anti-seizure medication primidone can be a helpful treatment in individuals with TRPM3. Beyond outlining the TRPM3 spectrum, our publication helped us find a long-awaited diagnosis for one of our research participants, one that took four years to prove. Here is the TRPM3 story. Continue reading
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.
HPO. SCN2A-related disorders represent one of the most common causes of neurodevelopmental disorders and developmental and epileptic encephalopathies (DEE). However, while a genetic diagnosis is easily made through high-throughput genetic testing, SCN2A-related disorders have such a broad phenotypic range that understanding the full scale of the clinical features has been traditionally difficult. In our recent study, we used a harmonized framework for phenotypes based on the Human Phenotype Ontology (HPO) to systematically curate phenotypic annotations in all individuals reported in the literature and followed at our center, a total of 413 unrelated individuals. Mapping phenotypic data onto 10,860 terms with 562 unique concepts and applying some of the computational tools we have developed over the last three years, we were able to delineate the phenotypic range in unprecedented detail. SCN2A is now the first DEE with all available data systematically curated and harmonized in a computable format, allowing for entirely novel insights. Continue reading
The other sodium channel gene. The week before Christmas, the Kiel group identified its first patient with SCN2A encephalopathy. At the same time, a questionably benign SNP in the same gene is haunting our Israel Epilepsy Family Project. Time to review the mysterious SCN2A gene that initially entered the scene as a candidate for a rare, benign familial epilepsy syndrome – only to return as one of the most prominent genes for autism, intellectual disability, and epileptic encephalopathies to date. Continue reading