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
Delayed rectifier. The discovery of de novo mutations in ion channel genes as a cause for genetic epilepsies continues. In a recent publication in Nature Genetics, we have identified de novo mutations in KCNA2 as a novel cause of epileptic encephalopathies associated with ataxia. Interestingly, even within a single gene, two different phenotypes seem to be emerging. Continue reading
GRIN2A. Mutations in several genes coding for NMDA receptor subunits have recently been found in various neurodevelopmental disorders. Amongst the different genes, GRIN2A is one of the most prominent ones and mutations in this gene are found in patients with epilepsy-aphasia syndromes. So far, we have mainly looked at GRIN2A from the epilepsy side. In a recent publication in Neurology, Turner and collaborators now examine the speech phenotype in GRIN2A families. They examine two families where speech issues are a prominent phenotypic feature. It turns out that GRIN2A mutations may predispose to a distinct speech phenotype. Continue reading
Structure. Despite tremendous advances in understanding its genetic underpinnings in the last few years, electrical status epilepticus during slow-wave sleep (ESES) is a poorly understood neurodevelopmental disorder and to a certain extent the prototype of an epileptic encephalopathy. Slow-wave sleep in affected children is entirely replaced by epileptiform activity, leading to significant neurocognitive impairment with an emphasis on speech impairment. In a recent publication in Annals of Neurology, alterations in CNKSR2 are identified in families with a more severe course of ESES, highlighting the postsynapse as a possible player in ESES pathogenesis. Continue reading
Torsional stress. The DNA double helix has one major problem that we know from telephone cords: it is difficult to untangle. However, our DNA is constantly twisted and untangled for gene transcription. This constant twisting and untwisting produces torsional stress that is relieved by topoisomerases. A recent publication in Nature Genetics now identified a human neurological phenotype that is caused by faulty activity of this mechanism: neurodegeneration with epileptic encephalopathy. However, there are some features of the phenotype that are not easily explained by erroneous DNA twisting. Continue reading
The GRIN2A triple. The idiopathic focal epilepsies are a group of childhood seizure disorders ranging from mild, self-limiting rolandic epilepsy to severe epileptic encephalopathies. The EEG feature of sharp-slow waves originating from the rolandic region is the unifying feature. As the rolandic region is part of the brain regions involved in speech production, acquired aphasia, i.e. loss of speech, can be a prominent feature in some patients. A strong genetic contribution in idiopathic focal epilepsies is assumed, but the genes involved have remained largely elusive. Now, three back-to-back publications in Nature Genetics highlight a prominent role of GRIN2A, probably the most counter-intuitive epilepsy gene ever found. 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.
Galvanize. Last week, the EuroEPINOMICS RES working groups made the final decisions for the selection of trios for exome sequencing at the Sanger Centre, funded jointly by the Sanger Programme on paroxysmal neurological disorders and the EuroEpinomics RES fund. We pushed the button for 102 patient-parent trios to be sequenced. And for some reason, I caught myself humming “Galvanize“, the 2005 big beat hymn by the Chemical Brothers. Continue reading