Silvia Paracchini: Dyslexia and Genetics
Dyslexia is an impairment in learning to read that affects up to 10% of children; it can have profound effects on an individual life. Dyslexia has an important genetic component; candidate genes control important stages during foetal brain development. Understanding the biology of dyslexia could help us design more effective diagnostic criteria and treatment plans.
Q: What is dyslexia?
SP: The word 'dyslexia' comes from Greek and it means 'impaired with words'. Clinically we define dyslexia as a specific impairment in learning to read which cannot be explained by any other obvious causes such as a neurological problem or lack of learning opportunities. It is very common and it affects up to 10% of school age children. We don't know what the biological causes of dyslexia are, but we know that even if dyslexia normally is diagnosed when a child starts going to school, dyslexia is there since birth. So the causes of dyslexia are to be found in the early stages of brain development.
Q: How much can dyslexia be blamed on our genes?
SP: Studies in families and especially in twins have consistently reported that genes account to as much as 70% in dyslexia development. This figure is telling us two important facts: first of all that genes do play an important part in dyslexia, but also that they are not the only contributor in this story. In fact dyslexia is a complex trait, and is likely to be the result of interplay of multiple factors of both genetic and environmental origin.
Q: Are other disorders linked to those genes?
SP: This is actually one of the questions I am trying answer with my current research. We know that children with dyslexia quite often show signs that are typical of other disorders. For example it is very common that a child diagnosed with dyslexia also show signs for Specific Language Impairment which is a specific condition of the development of language, or other disorders such as Attention Deficit Hyperactivity Disorder. So with my research I am trying to establish whether common genes can explain the co-occurrence of clinically distinct disorders.
Q: What are the most important lines of research that have developed over the past five or ten years?
SP: The last years have been very exciting in the field of dyslexia research. Different research groups have independently identified different susceptibility genes for dyslexia, but they all seem to point to the same biological pathway. It looks like genes conferring with dyslexia control very important stages during foetal brain development. These findings have now opened new research lines so we want to study what these genes actually do and how they contribute to dyslexia starting from their function during brain development. Another important observation has been the fact that the same genetic variants that have been reported to be associated with dyslexia also contribute to the reading abilities of the general population regardless of a clinical diagnosis for dyslexia. This has changed the definition of dyslexia a bit so we shouldn't really think about a black and white diagnosis, but we should think more of a gradient along a continuous range.
Q: Why does your line of research matter, why should we put money into it?
SP: Dyslexia can have profound effects on an individual life and these can be very long term. They are particularly important when dyslexia goes undetected. Typically a child grows frustrated and loses motivation and this can have a huge impact on his life. While it is quite obvious that dyslexia can have an impact on academic career and on job achievement, it is less obvious that dyslexia does also have an impact on social interaction and emotional life, often leading to conditions such as depression. It is estimated that dyslexia costs the UK £1billion a year to support all the long term challenges associated with failure to detect dyslexia earlier on, and this can range from problems at school, unemployment, antisocial behaviour to treatment of psychiatric conditions.
Q: How does your research fit into translational medicine within the Department?
SP: The aim of my research is to understand and identify the genetic components of dyslexia and then to understand the underlying biology. This fits with the general view of the Department that is investing lots of resources and effort in understanding the genetics underlying human common and complex traits. We know that dyslexia is a heterogeneous condition, so it is quite likely that different groups of patients or people with dyslexia will require different lines of treatment. For example we know that coloured lenses might help some children in learning to read, but may not benefit everybody. So understanding the biology of dyslexia will give us a tool to design more effective diagnostic criteria and treatment plans. This is obviously a long term goal. In the short term I think that this research is very important because it shows that dyslexia is a biological condition. Every now and then we hear debates challenging the existence of dyslexia or blaming parental education for it, and this is extremely frustrating for people with dyslexia. I am actively involved in making my research accessible to parents, teachers and therapists, and they all want to know what dyslexia really is. For example I have recently contributed to the science section to a book by Liz Dunoon. Liz is an Australian mum of dyslexic children and she wrote this book both to present parents with practical advice on how to deal with dyslexia, but also to make the latest advances in research accessible to a wider audience. This book had a huge success, received lots of media coverage and definitely contributed to a raised awareness about dyslexia. This went as far as bringing discussion about dyslexia at government level, and Liz is now very hopeful that with this book she is going to contribute to changing policy to support people with this disorder.