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.
What comes next. Earlier this month, Ingo made a bit of a splash at the American Epilepsy Society Annual Course, with his surprising comment that, in some contexts, “genes don’t matter.” This was in reference to transcripts and gene expression, which ultimately determine if and how variants can cause disease. In this post, I wanted to explore this idea, diving into the world of transcripts and their increasing relevance in approaching diagnosis and treatment of genetic epilepsies and neurodevelopmental disorders. And I wanted to share one of the most surprising findings in epilepsy genetics in 2022, namely, how examining transcripts rather than genes helped us understand how an intronic variant can be dominant-negative. Continue reading
N-of-1. The use of whole exome sequencing has led to many of the recent genes discovered in the epilepsy field. However, in contrast to established genes or emerging genes that are found in several patients, there is a significant proportion of patients who carry de novo mutations in novel genes. In many cases, these novel genes look very suspicious. One aspect of a recent publication in Genetics in Medicine was to assess how these suspicious candidates convert to established genes over time. Continue reading
Acetylcholine. The success story of identifying epilepsy genes started with familial frontal lobe epilepsies and the discovery of CHRNA4, coding for a subunit of the nicotinergic acetylcholine receptor. Ever since this initial discovery, other gene identifications have reinforced a dysfunction in cholinergic signaling as one of the key mechanisms in genetic frontal lobe epilepsies. A recent study in the Annals of Clinical and Translational Neurology now identifies a novel gene for familial frontal lobe epilepsies, coding for an anchoring protein for acetylcholinesterase (AChE), the key enzyme breaking down acetylcholine. Continue reading
GABA/glutamate. Even though large-scale Copy Number Variation (CNV) studies in schizophrenia, autism, and intellectual disability were en vogue only a few years ago, it became quiet around these type of studies more recently. Now, a recent study in Neuron revisits CNV analysis in schizophrenia with the largest sample size to date, cancelling out much of the noise that smaller studies had to fight with. Find out how the authors managed to demonstrate a contribution of the GABAergic and glutamatergic system to schizophrenia by sheer numbers. Continue reading
Issue 9/2015. This issue of the publications of the week is about novel genetic findings for neurological disorders that we usually don’t discuss on our blog. Given that there were several reports this week, I thought that thinking a bit outside the box would be a good theme for this week. Follow us on a brief journey of novel genes for Alzheimer’s disease, essential tremor, and agenesis of corpus callosum.
Issue 7/2015. I am realizing that we are a little behind with our weekly paper review and I hope that we can use the month of July to catch up. Our publications of the week include functional studies on CDKL5 targets that may suggest future therapy development, the recessive/de novo paradox of KIF1A and an attempt to understand the genetics of familial cortical tremor. Continue reading
Founder variant. Specific language impairment (SLI) is a common neurodevelopmental disorder, presenting as delays in acquiring language skills in children who have no hearing loss or other developmental delays. There is a strong genetic component, but the genetic architecture of SLI is entirely unknown. In a recent publication in PLOS Genetics, exome sequencing is performed in the founder population of the Robinson Crusoe Island where SLI is common. Using a combination of exome sequencing and association study, the autors identify a variant In NFXL1 as a plausible candidate for language delay. Continue reading
Doose Syndrome. In the early 1970s, a group of children with severe childhood epilepsies was found to have comparable clinical features that consisted of quick jerks and subsequent drop attacks amongst other types of epileptic seizures. These seizures, myoclonic-astatic or myoclonic-atonic seizures, eventually became the defining feature of an epilepsy syndrome referred to as Myoclonic Astatic Epilepsy or Doose Syndrome. In the recent issue of the American Journal of Human Genetics, we report on the first true gene for Doose Syndrome. Here is the story of SLC6A1 (GAT-1). Continue reading
Rare human knockouts. Recessive disorders arise when both copies of a causative gene are affected by mutations. These diseases are thought to be a very rare occurrence, but the cumulative impact of these conditions is not known. Population genome sequencing offers the possibility to assess the spectrum and distribution of potentially causative mutations in large groups of individuals. In a recent publication from deCODE published in Nature Genetics, the authors examine the population spectrum of rare human knockouts using the unique genetic data and population structure of the Icelanders. Here is the story about potential candidate genes identified by population genetics. Continue reading