Heterogeneity. Family-based exome sequencing or trio exome sequencing for de novo mutations is currently the method of choice to identify genetic risk factors in neurodevelopmental disorders. However, given the increasingly recognized variability in the human genome, the hunt for causative de novo mutations is sometimes an uphill battle – it is impossible to distinguish causal mutations from random events unless genes are affected repeatedly. In a recent publication in Nature, Fromer and colleagues present the most comprehensive search for de novo mutations in schizophrenia to date. They observe an incredible genetic heterogeneity that reflects the genetic architecture of neurodevelopmental disorders. Continue reading
Joining forces. The EuroEPINOMICS-RES consortium and Epi4K/EPGP are currently joining forces for genetic studies on epileptic encephalopathies. A first collaborative study focuses on de novo mutations in Infantile Spasms and Lennox-Gastaut-Syndrome. In the last two years, after decades of disappointment, we have finally managed to accomplish a breakthrough in understanding the genetic basis of epileptic encephalopathies. The method of trio-based exome sequencing works amazingly well to identify the genetic cause, and the field currently has the crucial momentum to reach the next level of research. Let’s briefly review why we need international collaborations to disentangle the genetic architecture of the epileptic encephalopathies. Continue reading
The de novo paradigm. De novo mutations play a significant role in many neurodevelopmental disorders including autism, intellectual disability and schizophrenia. In addition, several smaller studies have indicated a role for de novo mutations in severe epilepsies. However, unless known genes for human epilepsies are involved, findings from large-scale genetic studies are difficult to interpret. De novo mutations are also seen in unaffected individuals and only very few genes are observed more than once. Now, a publication in Nature by the Epi4K and EPGP collaborators uses a novel framework to tell pathogenic mutations from genomic noise. Their study provides very strong evidence for a predominant role of de novo mutations in Infantile Spasms and Lennox-Gastaut Syndrome. Continue reading
Share or be shared. During the last two weeks, the RES consortium has approved a new data sharing policy that will allow us to work with increased transparency and accountability within our upcoming projects. This new data sharing policy is a consequent extension of the previous protocols we had in earlier consortia – with one major difference. This time, it’s in writing. While we are getting ready to tackle the large dataset on epileptic encephalopathies released by the Sanger Institute, we took a moment to talk about how things should be running.
Taking things apart. Looking for de novo variants using trio exome sequencing is a powerful technique to identify disease-related genes. After having introduced samtools during the last post, this will be post 2/3 in a series on how to perform an analysis of exome data for de novo variants. This time, I would like to take apart the methods that take us from Gigabyte BAM files to small tables with likely variants. So buckle up. Continue reading