Bipolar Disorder Symptoms Linked To Gene Variant

A gene variant has been linked to both psychotic symptoms and cognitive impairment in those with bipolar disorder, according to a recent study.

Researchers at the Karolinska Institutet and the Sahlgrenska Academy at Gothenburg University in Sweden found that the gene variant affects levels of a protein in the brain-suggesting biochemical changes and clinical symptoms related to heritable psychiatric disorders.

"We've identified a gene variant linked to specific psychotic symptoms and cognitive impairment in people with bipolar disorder," says Mikael Landén, researcher at Karolinska Institutet's Department of Medical Epidemiology and Biostatistics and the Sahlgrenska Academy's Department of Neuroscience and Physiology, in a news release. "The link to cognitive symptoms is particularly interesting, since there are no treatments currently available to improve problems with attention, memory and concentration, which impact heavily on functional outcome and recoverability."

During the study, researcher examined participants with bipolar disorder from the St. Göran project, which is run in Stockholm and Gothenburg. Along with mapping participants' specific symptoms, researchers also tested their cognitive abilities and measured different levels of blood proteins and CSF--a fluid that encases the brain and that can provide a good indication of its overall chemistry. 

On performing a genome-wide association study (GWAS), findings revealed that a genetic variant of the gene SNX7 was linked to the levels of a protein in the CSF, known as kynurenic acid, and disease symptoms.

"We then conducted a series of supplementary experiments to identify a probable signal pathway, from the occurrence of the genetic risk variant to clinical symptoms in the form of psychosis and cognitive impairment," said Landén. "The pathway mainly involves signalling via the brains' immune cells, and thus differs from how today's drugs operate. What we're hoping, therefore, is that the new mechanisms we've discovered will help in the development of more targeted drugs, where existing immune-modulating drugs can also be of interest."

The study is published in the journal Molecular Psychiatry.

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