It appears that variations in the CLOCK gene do not play a major role in the development of schizophrenia, bipolar disorder, or major depressive disorder (MDD), conclude Japanese investigators.

Clock genes not only regulate circadian rhythms but also have an influence on dopamine neural transmission, and it is thought that abnormalities in both of these systems are associated with schizophrenia, bipolar disorder, and MDD. Furthermore, there is evidence that CLOCK is linked to these conditions.

To investigate further, Taro Kishi, from Fujita Health University School of Medicine in Aichi, and colleagues genotyped 733 schizophrenia patients, 149 bipolar disorder patients, 324 MDD patients, and 795 healthy controls for the six tagging single nucleotide polymorphisms (SNPs) in CLOCK.

There were no overall associations between the tag SNPs and schizophrenia, bipolar disorder, or MDD. Exploration of gender differences revealed an association between one SNP and schizophrenia in women, although this did not survive Bonferroni correction.

The researchers also report in the European Archives of Psychiatry and Clinical Neuroscience that that there were no gender associations between any of the studied SNPs and MDD or bipolar disorder.

They suggest: “CLOCK may not play a major role in the pathophysiology of schizophrenia, bipolar disorder, and MDD in the Japanese population. However, it will be important to replicate and confirm these findings in other independent studies using larger samples.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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