CLOCK gene variants associate with sleep duration in two independent populations.

Allebrandt KV, Teder-Laving M, Akyol M, Pichler I, Müller-Myhsok B, Pramstaller P, Merrow M, Meitinger T, Metspalu A, Roenneberg T. Biol Psychiatry. 2010 Jun 1;67(11):1040-7.

To investigate the relationship between sleep duration and clock gene polymorphisms, a pair of genetic association studies and a meta-analysis of the two were performed. The first association study was performed in 333 participants from Northern Italy who were recruited from the MICROS study. A second replication study was performed in participants recruited from the Estonian genome project who had very long (>8.5 hours) or very short (<7 hours) sleep durations, as determined by the Munich ChronoType Questionnaire. A meta-analysis of the results from each of the two populations found that the rs12649507 SNP in clock was associated with sleep duration and the rs12649507-rs11932595 GGAA clock haplotype was associated with long sleep duration.

rs12649507-rs11932595 in clock

clock rs12649507-rs11932595

NCBI Variation Viewer rs12649507-rs11932595

Screening of clock gene polymorphisms demonstrates association of a PER3 polymorphism with morningness-eveningness preference and circadian rhythm sleep disorder

Hida A, Kitamura S, Katayose Y, Kato M, Ono H, Kadotani H, Uchiyama M, Ebisawa T, Inoue Y, Kamei Y, Okawa M, Takahashi K, Mishima K. Sci Rep. 2014 Sep 9;4:e6309.

In order to assess the relationship between genetics and chronotype, the authors performed a study involving 1174 subjects recruited from medical centres in mainland Japan. The subjects were genotyped and given the Horne–Östberg Morningness–Eveningness Questionnaire to determine their chronotype.

It found that having the per3 SNP rs228697 is associated with being a morning chronotype, as well as being a free running chronotype. However, these results may simply be false discoveries since the significance tests for association were not adjusted for the many tested hypotheses.

rs228697 in per3

 per3 rs228697

NCBI Variation Viewer rs228697

Association between CLOCK 3111T/C and preferred circadian phase in Korean patients with bipolar disorder

Lee KY, Song JY, Kim SH, Kim SC, Joo EJ, Ahn YM, Kim YS. Prog Neuropsychopharmacol Biol Psychiatry. 2010 Oct; 34 (7): 1196–1201.

A study of 610 Koreans  was performed to determine whether circadian preferences and bipolar disorder can be influenced by genetics. It found a significant positive association between the rs1801260 SNP in the clock gene and bipolar disorder. The authors also discovered a trending but not significant relationship between this SNP and extreme morning or evening chronotype as measured by the Composite Scale of Morningness questionnaire.

rs1801260 in clock

 Clock rs1801260

NCBI Variation Viewer rs1801260