Living in Cologne is a little tough at the moment. Currently, we are in the middle of the Cologne Carnival, the world’s oldest carnival, which started in 1829. Until the upcoming Wednesday the entire city is one big festival. In addition to the 1 million Cologne citizens probably another million tourists will join. Due to this (positive) distraction I will write less than usual. However, I still consider this week’s publications noteworthy. Continue reading
CNS metabolism Neuronal activity accounts for 80% of the brain’s energy consumption. Blood-borne glucose is an essential energy source for the adult human brain. Both neurons and astrocytes take up glucose via the cell-specific transporters GLUT1 and GLUT3. Upon increased demand neurons ability to take up glucose is limited and lactate provided by astrocytes becomes the primary oxidative fuel. Under certain conditions the brain can also utilize acetoacetate, b-hydroxybutyrate and acetone (ketone bodies) derived from fatty acids as alternative energy source. Neurons metabolize ketone bodies to Acetyl-CoA, which is further oxidized through the TCA cycle. High circulating levels of ketone bodies are known to protect the brain. Ketone bodies also prevent seizures in GLUT1 difficiency syndrome and are important for brain development, but cellular and molecular mechanisms underlying the protective effect of ketone bodies are not yet fully clear. In the following I discuss the presumable link of metabolism with epigenetic changes and implications in brain function.
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
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
A productive week in epilepsy genetics. Scientists and editors were certainly busy this week reporting novel variants and deletions as well the experimental and statistical advances for their interpretation.
A de novo GRIN2A missense mutation in early-onset epileptic encephalopathy. We and others have associated variants affecting the GRIN2A gene with a range of childhood focal epilepsy syndromes. Continue reading
Missing heritability. The concept of missing heritability is often invoked to demonstrate that existing genetic techniques only identify a fraction of the overall genetic risk for human diseases including the epilepsies. This statement implicitly assumes that we have a good and solid understanding of what the magnitude of genetic risk actually is. However, when looking at the epidemiological studies that have investigated familial risk of epilepsy, some of these studies have inherent problems, including small sample sizes, different phenotype definitions, recruitment bias, and lack of controls. A recent study in Brain now reassesses the familial risk of epilepsy in a population-based cohort of the Rochester Epidemiology Project. There are few instant classics in the field of epilepsy genetics – this study is one of them. Continue reading
Milestones. Today I passed my board exam for pediatric neurology or neuropediatrics, as we call it in Germany. Even though I am usually not big on celebrating occasions like this, I wanted to use this blog post to reflect upon a journey that led me to three different continents and started eleven years ago in the foothills of Appalachia. Continue reading
Join the genome hacking league. We are preparing a EuroEPINOMICS bioinformatics workshop in Leuven and I really, really encourage you to join us, as there are handful of place left. This will be the workshop that I always wanted to attend, but never got a chance to take part in. And yes, there is a final exam, but there is a chance that you might pass it. If you’re worried, skip ahead two paragraphs.
Update. I re-read one of my older posts when I went through Dennis’ recent discussion on the lessons learned during his PhD, which also included his advice on how to keep your motivation up. Two years ago, I actually wondered where motivation for science comes from in general. Are we driven largely by egoistic motives like money or fame, or are there different factors at play? I am re-blogging one of our old posts from 2012 with minor 2014 updates. These were the answers that I came up with back then. I think they are still relevant. Continue reading