The microdeletion landscape of Genetic Generalized Epilepsy

CNV. Structural genomic variations or Copy Number Variations (CNVs) significantly contribute to the genetic architecture of many neurodevelopmental disorders. However, given the enormous variation in the human genome in healthy individuals, the precise contribution of CNVs remains poorly understood. In a recent publication in PLOS Genetics, we were able to assess the microdeletion architecture in more than 1,000 patients with Genetic Generalized Epilepsy (GGE) compared to more than 5,000 controls. We found that microdeletions occur almost twice as often in GGE patients compared to controls, an analysis that revealed both known suspects and interesting candidates. Continue reading

Publications of the week: SLC13A5, SNAP25, and JME fMRI endophenotypes

Catching up. It has been a while since we posted a section on the recent publications in the field of epilepsy genetics. We are trying to catch up by briefly discussing three publications that appeared in the last two weeks. Here is what you should know about citrate transporters in epileptic encephalopathy, an STXBP1-interacting protein, and fMRI endophenotypes in Juvenile Myoclonic Epilepsy (JME). Continue reading

Identifying core phenotypes – epilepsy, ID and recurrent microdeletions

Triad. There are three microdeletions in particular that increase the risk for the Idiopathic/Genetic Generalized Epilepsies (IGE/GGE). This triad includes microdeletions at 15q13.3, 16p13.11 and 15q11.2, which are hotspot deletions arising from the particular architecture of the human genome. While the association of these microdeletions with epilepsy and other neurodevelopmental disorders including autism, intellectual disability and schizophrenia is well established, the core phenotype of these variants remains elusive, including the question whether such a core phenotype actually exists. In a recent paper in Neurology, Mullen and collaborators zoom in on a possible core phenotype of these microdeletions. The authors investigate a phenotype in which these microdeletions are particularly enriched: generalized epilepsy with intellectual disability. Continue reading

The endozepine mystery

Compound unknown. GABA is the main inhibitory neurotransmitter in the Central Nervous System and its effect is mediated through GABA receptors. Benzodiazepines are compounds that reinforce the action of GABA in the brain, which gives them antiepileptic properties. Consequently, benzodiazepines are one of the most common groups of antiepileptic drugs used to interrupt acute epileptic seizures. Interestingly, benzodiazepines have their own binding site on the GABA receptor, suggesting that they might actually mimic the effect of another, yet unknown substance that is present in the brain. The identity of this mysterious substance, the endogenous benzodiazepine or endozepine, has been one the romantic mysteries of neuroscience. Now, a recent paper in Neuron provides strong evidence that products of the DBI gene are the long-sought endozepine. Continue reading

Standing on the shoulders of giants: the EPICURE GWAS on Idiopathic Generalized Epilepsy

Pushing the reset button. The history of epilepsy genetics can broadly be distinguished into two major eras: the time before September 4th, 2012 and everything after this. September 4th, 2012 was the date that the first large genome-wide association study in IGE/GGE was published online in Human Molecular Genetics. Each of the >100 association studies in IGE listed in PubMed is now dated and needs to measure up against the current study, which will likely be remembered as the “EPICURE study”. The results of the EPICURE study are surprising and upset our conventional wisdom of what causes one of the most common forms of epilepsy. Continue reading