Major depressive disorder: A loss of circadian synchrony?

• Published in: BioEssays Vol. 35; no. 11; pp. 940 - 944
• Main Authors: Edgar, Nicole, McClung, Colleen A.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.11.2013; Wiley Subscription Services, Inc
• Subjects: Brain; Brain - metabolism; Circadian rhythm; Circadian Rhythm - genetics; Circadian rhythms; depression; Depressive Disorder, Major - genetics; Depressive Disorder, Major - metabolism; Gene expression; Gene Expression Regulation; Genetic factors; Humans; Mental depression; Microarray Analysis; post-mortem; Suprachiasmatic Nucleus - metabolism; circadian rhythms; depression; post-mortem
• ISSN: 0265-9247; 1521-1878; 1521-1878
• DOI: 10.1002/bies.201300086

Circadian rhythms in the sleep/wake cycle, along with a range of physiological measures, are severely disrupted in individuals with major depressive disorder (MDD). Moreover, several central circadian genes have been implicated as potential genetic factors underlying the illness through candidate gene studies and some genome wide association studies. However, investigations into the molecular underpinnings of circadian disturbances in the human brain have been quite challenging. In their recent publication, Li and colleagues have used a novel approach to determine the rhythmic patterns of circadian gene expression in several regions of the human brain, and how these patterns are disrupted in MDD. Their findings demonstrate that in healthy subjects, several brain regions outside the suprachiasmatic nucleus (the master clock) exhibit diurnal gene expression patterns that are disrupted in the brains of MDD subjects. These findings will provide the foundation for future studies of gene‐specific drug targets, and biomarkers for the disease. Li and colleagues organized microarray data from human post‐mortem brain tissue in a pseudo‐time series to examine molecular rhythms. They revealed that healthy subjects have strong diurnal gene expression patterns in several brain regions outside the SCN, and these patterns are significantly disrupted in subjects with major depressive disorder.