A missense variation in human casein kinase I epsilon gene that induces functional alteration and shows an inverse association with circadian rhythm sleep disorders.
Recent studies have shown that functional variations in clock genes, which generate circadian rhythms through interactive positive/negative feedback loops, contribute to the development of circadian rhythm sleep disorders in humans. Another potential candidate for rhythm disorder susceptibility is casein kinase I epsilon (CKIepsilon), which phosphorylates clock proteins and plays a pivotal role in the circadian clock. To determine whether variations in CKIepsilon induce vulnerability to human circadian rhythm sleep disorders, such as delayed sleep phase syndrome (DSPS) and non-24-h sleep-wake syndrome (N-24), we analyzed all of the coding exons of the human CKIepsilon gene. One of the variants identified encoded an amino-acid substitution S408N, eliminating one of the putative autophosphorylation sites in the carboxyl-terminal extension of CKIepsilon. The N408 allele was less common in both DSPS (p = 0.028) and N-24 patients (p = 0.035) compared to controls. When DSPS and N-24 subjects were combined, based on an a priori prediction of a common mechanism underlying both DSPS and N-24, the inverse association between the N408 allele and rhythm disorders was highly significant (p = 0.0067, odds ratio = 0.42, 95% confidence interval: 0.22-0.79). In vitro kinase assay revealed that CKIepsilon with the S408N variation was approximately 1.8-fold more active than wild-type CKIepsilon. These results indicate that the N408 allele in CKIepsilon plays a protective role in the development of DSPS and N-24 through alteration of the enzyme activity.
Takano
Atsuko
A
Division of Protein Metabolism, Institute for Protein Research, Osaka University, Osaka, Japan.
Uchiyama
Makoto
M
Kajimura
Naofumi
N
Mishima
Kazuo
K
Inoue
Yuichi
Y
Kamei
Yuichi
Y
Kitajima
Tsuyoshi
T
Shibui
Kayo
K
Katoh
Masaaki
M
Watanabe
Tsuyoshi
T
Hashimotodani
Yuki
Y
Nakajima
Toru
T
Ozeki
Yuji
Y
Hori
Toru
T
Yamada
Naoto
N
Toyoshima
Ryoichi
R
Ozaki
Norio
N
Okawa
Masako
M
Nagai
Katsuya
K
Takahashi
Kiyohisa
K
Isojima
Yasushi
Y
Yamauchi
Toshio
T
Ebisawa
Takashi
T
D000328:Adult; D000483:Alleles; D048149:Casein Kinase 1 epsilon / Q000235:genetics*; D002940:Circadian Rhythm / Q000235:genetics*; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D005838:Genotype; D006801:Humans; D007438:Introns / Q000235:genetics; D007700:Kinetics; D008297:Male; D020125:Mutation, Missense / Q000235:genetics*; D010766:Phosphorylation; D018807:Polymorphism, Single-Stranded Conformational; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012307:Risk Factors; D012893:Sleep Wake Disorders / Q000235:genetics*
D018076:DNA, Complementary; D048149:Casein Kinase 1 epsilon