WGS. Whole-genome sequencing is increasingly used to understand the cause of rare diseases in a research and diagnostic context. However, while the usefulness of this technology has been shown in smaller studies, it remains unclear whether strategies to understand the cause of rare disorders through whole genome sequencing can be performed on a national level. A recent study in Nature reported the first results from a national sequencing campaign for rare disorders in the UK, including the analysis of more than 13,000 genomes. In this blog post, I would like to focus on the neurogenetics component of this enormous study, which identified disease-causing variants in GNAO1 as the most common cause within the study’s subgroup of neurological and developmental disorders. Continue reading
Tag Archives: GNAO1
Dynamin 1, the synapse, and why epilepsy gene discovery is now officially over
E2 consortium. Infantile Spasms and Lennox-Gastaut Syndrome are two epilepsy syndromes with a strong genetic component. De novo mutations play an important role in genetic epilepsies. However, given the overall mutational noise in the human genome, telling causative genes from innocent bystanders is difficult. In the largest and most comprehensive analysis so far, our E2 consortium just published a joint analysis of 356 patient-parent trios, which were analyzed by exome sequencing. In addition to implicating DNM1, GABBR2, FASN, and RYR3, this publication sends a clear message: the age of gene discovery in epilepsy is over – from now on, genes will find themselves. Let me tell you what I mean by this. Continue reading
The OMIM epileptic encephalopathy genes – a 2014 review
EIEE1-19. Online Mendelian Inheritance in Man (OMIM) is one of the most frequently accessed online databases for information on genetic disorders. Genes for epileptic encephalopathies are organized within a phenotypic series entitled Early Infantile Epileptic Encephalopathy (EIEE). The EIEE phenotypic series currently lists 19 genes (EIEE1-19). Let’s review the evidence for these genes as of 2014. Continue reading
Treatable causes of intellectual disability and epilepsy that you don’t want to miss
Think metabolic. We have discussed de novo mutations as a cause of epileptic encephalopathies repeatedly on our blog. While there is emerging evidence that de novo mutations in established genes such as SCN1A or CDKL5 or novel genes including GNAO1 or CHD2 are a major cause of genetic morbidity in patients with epileptic encephalopathies, investigations for de novo mutations are not the immediate knee-jerk reaction in clinical practice. In fact, if a child presents with an epileptic encephalopathy, excluding inborn errors of metabolism (IEM) takes priority. While metabolic causes of epileptic encephalopathies are rare, they need to be excluded as some of these conditions are treatable. In a recent review in Molecular Genetics and Metabolism, van Karnebeek and colleagues review the 89 causes of intellectual disability that are potentially treatable. Many of these conditions also present with epilepsy. They present an updated diagnostic algorithm and provide an online resource for these conditions – in a nutshell, there is an app for that. Continue reading
Infantile Spasms/Lennox-Gastaut genetics goes transatlantic
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
G proteins, GNAO1 mutations and Ohtahara Syndrome
G proteins. Intracellular signaling in neurons can occur through various mechanisms including so-called second messengers. G proteins constitute an important part of the signaling cascade that translates the signal from membrane-bound receptors. On neurons, GABA-B receptors or alpha-2 adrenergic receptors use signal transduction through the so-called G alpha-o proteins, which are particularly abundant in the CNS and encoded by the GNAO1 gene. Now a recent paper in the American Journal of Human Genetics describes de novo mutations in Ohtahara Syndrome and movement disorders. Continue reading
