What have gene expression studies increase understanding of the pathophysiology of bipolar affective disorder (manic-depressive illness)?

Updated: May 30, 2019
  • Author: Stephen Soreff, MD; Chief Editor: Glen L Xiong, MD  more...
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Gene expression studies are one way of measuring the relative activity or inactivity of genes, and they have already been proven useful for illuminating the pathophysiology of psychiatric disorders, including bipolar disorder. For example, studies comparing specific regions of postmortem brain tissue from persons with bipolar disorder with tissue from control subjects have consistently shown that levels of expression of oligodendrocyte-myelin–related genes appear to be decreased in brain tissue from persons with bipolar disorder. [33, 34, 35, 36] As with genetic studies, gene expression profiling studies require very large sample sizes to produce replicable data. Furthermore, they must focus on the correct brain region(s) thought to be functioning differently in bipolar disorder, a point still under some debate. Therefore, research in this area is ongoing and frequently subject to update.

Oligodendrocytes produce myelin membranes that wrap around and insulate axons to permit the efficient conduction of nerve impulses in the brain. Therefore, loss of myelin is thought to disrupt communication between neurons, leading to some of the thought disturbances observed in bipolar disorder and related illnesses. Brain imaging studies of persons with bipolar disorder also show abnormal myelination in several brain regions associated with this illness. [37, 38] It can be useful to compare data from gene expression studies with brain imaging studies of persons with bipolar disorder to determine whether abnormalities of structure or function correlate with changes in gene expression. In this case, structural neuroimaging studies also show abnormal myelination in several brain regions associated with bipolar disorder. [37, 38] Of note, many widely used psychotropic treatments including those for bipolar disorder share signaling pathways that affect myelination, its plasticity, andrepair;such pathways may promote myelination of neurons. [39]


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