The second ILAE GWAS or why 30% of genetic generalized epilepsy is explained

Genome-wide association. While most of the neurogenetics community was focused on exome sequencing and the discovery of novel monogenic forms of epilepsy in the last few years, something quite remarkable had happened in the background. Common variants and genome-wide association studies have made a remarkable comeback. The ILAE Consortium for Complex Epilepsy had slowly worked on increasing sample sizes over time, and the second analysis of common variants in common epilepsies was published in late 2018. Sample sizes have almost doubled since the first study in 2014, and as a result, the number of genome-wide significant loci has tripled. However, the most intriguing finding was something that completely caught me by surprise – more than 30% of the heritability of the genetic generalized epilepsies is explained through common variants, approaching the numbers we see in epileptic encephalopathies explained by monogenic causes. This is one more reason to discuss the recent ILAE GWAS in more detail. Continue reading

A polygenic trickle of common variants in neurodevelopmental disorders

Common variants. In addition to the gradual increase in gene discovery due to exome sequencing, there is a field of human genetics developing in parallel that we have not paid much attention to recently. The role of common genetic variants or Single Nucleotide Polymorphisms (SNP) was initially limited to genome-wide association studies, looking at single variants individually. However, more recently, common variants have been assessed jointly in various diseases, resulting in so-called polygenic scores. In a recent publication in Nature, the polygenic contribution to neurodevelopmental disorders is evaluated. Interestingly, there seems to be a very robust contribution of common variants in neurodevelopmental disorders, even in patients with known de novo variants. Here is a brief discussion on why common variants start getting interesting for the neurogenetics field again. Continue reading