Schizophrenia and bipolar disorder may have a similar genetic cause in reduced expression of genes responsible for myelin production in the central nervous system, according to an article in the September 6th issue of the Lancet.
Previous research has suggested abnormalities in expression of lipid- and myelin-related genes in schizophrenia. Oligodendrocytes produce the myelin (which is 80 percent lipid and 20 percent protein) that sheaths axons in the central nervous system and makes possible efficient conduction of nerve impulses.

Sabine Bahn, PhD, and her British colleagues investigated oligodendrocyte-specific gene expression related to myelin and myelination in the preserved brains of 15 people who had had schizophrenia, 15 who had had bipolar disorder, and a control group of 15 brains from people who had not had either disorder.

The investigators used sensitive mRNA-based techniques (namely, polymerase chain reaction and microarray assessment) to compare gene expression in the preserved brains of 15 people who had had schizophrenia, 15 who had had bipolar disorder, and a control group of 15 brains from people who had not had either disorder.

There was a clear reduction of expression of key oligodendrocyte-related and myelin-related genes in the brains of patients with schizophrenia or bipolar disorder; the gene-expression changes showed a high degree of overlap for the 2 disorders. There was strong correlation with results obtained with microarray analysis compared with those obtained by quantitative polymerase chain reaction.

Sabine Bahn commented, "We believe that our results provide strong evidence for oligodendrocyte and myelin dysfunction in schizophrenia and bipolar disorder. Expression profiles of most known oligodendrocyte-specific and myelin-associated genes were greatly reduced, and several transcription factors known to coordinate myelin gene expression showed corresponding alterations. The high degree of correlation between the expression changes in schizophrenia and bipolar disorder provide compelling evidence for common pathophysiological pathways that may govern the disease phenotypes of schizophrenia and bipolar disorder. I would like to add that this research would not have been possible without the support of the Stanley Medical Research Institute."

In an accompanying Commentary, Dr. Kenneth L Davis stated, "The observation that at least some myelin-related gene-expression deficits are common between individuals with schizophrenia and bipolar disorder is intriguing because schizophrenia and bipolar disorder have different symptom profiles and require treatment based on quite different neurotransmitter systems."