Wiring the Brain

Source Many people, scientists and non-scientists alike, object to what they perceive as genetic determinism . This is often a reaction to geneticists apparently over-reaching and claiming that some trait or condition is “caused by” a single gene. A common rejoinder is that any biological process obviously involves many hundreds of gene products, interacting with each other in complex ways and so it is nonsense to say that the trait is determined by a single gene. That is absolutely true, if you are using the word “gene” purely in the molecular biology sense – as a piece of DNA that encodes a particular product (usually a protein). But geneticists also use it in the original sense, as a unit of heredity – a genetic variant or mutation that can be passed on across generations and that influences some phenotype. Genetics is not about how a characteristic arises, it is about how variation in that characteristic arises. For example, when you are describing someone, you m...

Did I miss a memo? Has eugenics somehow become respectable again? Source There has been a lot of talk lately, in the blogosphere at least ( 1 , 2 , 3 , 4 , 5 ), about the idea of using molecular genetics to predict and select for higher intelligence in humans (through pre-implantation screening of embryos, for example). The prevailing view among many discussing this idea seems to be that if we can do it, we obviously should do it. The casualness with which this conclusion is reached is astonishing to me, given the history of humanity’s efforts in this area. To many commentators, it seems to be a given that having more intelligent people, across the population, is not only obviously a good thing, but one that supersedes any other considerations. Selecting for increased intelligence doesn’t sound so bad, when you phrase it like that, until you realise that it actually involves the converse – selecting against individuals with lower predicted intelligence. I am not ascribin...

Source Why are some brain disorders so common? Schizophrenia, autism and epilepsy each affect about 1% of the world’s population, over their lifetimes. Why are the specific phenotypes associated with those conditions so frequent? More generally, why do particular phenotypes exist at all? What constrains or determines the types of phenotypes we observe, out of all the variations we could conceive of? Why does a system like the brain fail in particular ways when the genetic program is messed with? Here, I consider how the difference between “concrete” and “emergent” properties of the brain may provide an explanation, or at least a useful conceptual framework There is now compelling evidence that disorders like epilepsy, schizophrenia and autism can be caused by mutations in any of a very large number of different genes (sometimes singly, sometimes in combinations). This is fundamentally changing the way we think about these disorders. It is no longer tenable...

This post first appeared as part of a SpotOn NYC special event on Communication and the Brain (March 2013), on nature.com.   When I started the Wiring the Brain blog a few years ago, it was with the intention of writing mainly for students, scientists and clinicians in the fields of genetics and neuroscience. Many of the posts deal with advances in our scientific understanding of the causes of neurodevelopmental and psychiatric disorders. Perhaps because of that, or just due to general interest in the broader themes, the blog has also become widely read by non-specialists. This presents some exciting opportunities to write in a different way and to convey the excitement of the field of neurogenetics to the general public, but also raises some particular challenges. The biggest difference I have found is that the assumption of a shared, global perspective is not always valid. When writing for scientific colleagues there is an implicit expectation of a c...

In Part 1 of this blog, I considered the various definitions of the term epigenetics and the confusion that can arise when they are conflated. Molecular epigenetic mechanisms modify chromatin structure and provide a means to stabilize a particular profile of gene expression. They also allow that profile to be passed on to a cell’s descendants, through mitosis . For this reason, epigenetic profiles have been called “heritable” (meaning through cell division). It is easy to see how that definition can be extrapolated to the idea that epigenetics could provide a means of heredity from one generation to the next. This idea has attracted substantial interest, with many people seeming to think it overturns classical genetics (the inheritance of characters based on DNA sequence), and rehabilitates Lamarckian evolution by supplying a respectable molecular mechanism. This view has gained particular prominence of late in the study of behaviour and psychiatry, with th...