Link between bipolar disorder and genetic mutations
By Liz Lockhart
Led by researchers from the University of California, San Diego School of Medicine, an international team 
of scientists reports that abnormal sequences of DNA play a significant role in the risk of the early onset of bipolar disorder.
These abnormal sequences of DNA are known as rare copy number variants or CNVs. The findings can be found in the December issue of the journal Neuron.
CNVs are genomic alterations of sections of DNA which involve too few or too many copies. These genetic mutations are not inherited from parents and significantly increase the risk for some neuropsychiatric conditions such as autism spectrum disorders and schizophrenia. Their role was uncertain in bipolar disorder.
Jonathan Sebat, PhD, the principal investigator and colleagues found that ‘de novo’ CNVs contribute considerable genetic risk in around 5% of early onset bipolar disorder which occurs in childhood and early adulthood.
The study’s first author, Dheeraj Malhotra, assistant project scientist in Sebat’s lab said that ‘having a ‘de novo’ mutation increases the chances of having an earlier onset of the disease.’
However, the cause or causes of bipolar disorder are still unclear. There would seem to be a clear genetic component which means that the disease runs in families, but previous studies that have centred on common inherited variants have had limited success when it comes to identifying key susceptibility genes.
While these new findings do not conclusively pin point a specific gene or genomic region, they do show convincing evidence that rare copy number mutations strongly contribute to the development of early onset bipolar disorder, Malhotra said.
He also said that the sequencing of complete genomes or exomes of large numbers of bipolar families is needed to determine the total genetic contribution of also forms of ‘de novo’ mutations to risk for bipolar disorder.
