Endophenotypes in bipolar disorder.
The search for genes in bipolar disorder has provided numerous genetic loci that have been linked to susceptibility to developing the disorder. However, because of the genetic heterogeneity inherent in bipolar disorder, additional strategies may need to be employed to fully dissect the genetic underpinnings. One such strategy involves reducing complex behaviors into their component parts (endophenotypes). Abnormal neurophysiological, biochemical, endocrinological, neuroanatomical, cognitive, and neuropsychological findings are characteristics that often accompany psychiatric illness. It is possible that some of these may eventually be useful in subdefining complex genetic disorders, allowing for improvements in diagnostic assessment, genetic linkage studies, and development of animal models. Findings in patients with bipolar disorder that may eventually be useful as endophenotypes include abnormal regulation of circadian rhythms (the sleep/wake cycle, hormonal rhythms, etc.), response to sleep deprivation, P300 event-related potentials, behavioral responses to psychostimulants and other medications, response to cholinergics, increase in white matter hyperintensities (WHIs), and biochemical observations in peripheral mononuclear cells. Targeting circadian rhythm abnormalities may be a particularly useful strategy because circadian cycles appear to be an inherent evolutionarily conserved function in all organisms and have been implicated in the pathophysiology of bipolar disorder. Furthermore, lithium has been shown to regulate circadian cycles in diverse species, including humans, possibly through inhibition of glycogen synthase kinase 3-beta (GSK-3beta), a known target of lithium.
Lenox
Robert H
RH
Neuropsychopharmacology Program, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
Gould
Todd D
TD
Manji
Husseini K
HK
D000818:Animals; D001714:Bipolar Disorder / Q000188:drug therapy / Q000235:genetics*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D002940:Circadian Rhythm / Q000235:genetics; D018913:Event-Related Potentials, P300; D020022:Genetic Predisposition to Disease; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D006801:Humans; D007963:Leukocytes, Mononuclear; D008094:Lithium / Q000627:therapeutic use; D010641:Phenotype; D015398:Signal Transduction / Q000502:physiology; D012892:Sleep Deprivation
D000697:Central Nervous System Stimulants; D008094:Lithium; D038341:Glycogen Synthase Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D038362:Glycogen Synthase Kinase 3