Kandel gives a description of one of the big biological discoveries from recent years, namely copy number variations, and explores what they might tell us about the development of psychiatric disorders:
One major advance has been the discovery that there is much more variability in the genome than had been anticipated, and that this takes the form of copy number variation (CNV). These are duplications or deletions of segments of a chromosome, often involving several or tens of genes, that enhance or depress the actions of specific genes. A well-known example of a CNV is the extra copy of chromosome 21 resulting in Down syndrome. It has recently been discovered that this type of variation is extremely common in everyone’s genome.
As he goes on to explain, CNVs have caused a lot of excitement in the world of mental illness research, not least because they’ve been found to occur in ‘out of the blue’ cases of schizophrenia – people without a family history of the disorder – suggesting that the disorder could be partially explained in some people by DNA ‘lesions’.
Some rare CNVs have been found to greatly increase the risk for schizophrenia, but unfortunately they don’t help explain the genetics of schizophrenia in general because there are many people with schizophrenia who don’t have these rare CNVs.
Nevertheless, this rare CNV finding may help us understand the neurobiology of the disorder by giving us clues based on how these unusual copy variations affect brain growth and protein expression.
Interestingly, those CNVs which have been found to increase the risk of schizophrenia also increase the risk for other disorders such as autism and intellectual disability (what the Americans call ‘mental retardation’) – suggesting that our diagnostic divisions between disorders may not be well supported by genetics.
Despite the title of the article, Kandel also highlights recent developments in psychotherapy, which have given us far the biggest advance in effective treatments for mental disorders in recent years.
Newsweek seem to have just released a whole collection of articles on biomedical sciences of which Kandel’s contribution is a part. But don’t miss a good article on ‘how science will enhance your brain’ and another piece on epigenetics.
Look on the right hand side for links to all the articles in the series.