Association of Per3 length polymorphism with bipolar I disorder and schizophrenia
Received 4 September 2014
Accepted for publication 1 October 2014
Published 9 December 2014 Volume 2014:10 Pages 2325—2330
Checked for plagiarism Yes
Review by Single-blind
Peer reviewer comments 5
Editor who approved publication: Dr Roger Pinder
Ramanujam Karthikeyan,1 Ganapathy Marimuthu,1 Chellamuthu Ramasubramanian,2 Gautham Arunachal,2 Ahmed S BaHammam,3 David Warren Spence,4 Daniel P Cardinali,5 Gregory M Brown,6 Seithikurippu R Pandi-Perumal7
1Department of Animal Behaviour and Physiology, School of Biological Sciences, Madurai Kamaraj University, Madurai, India; 2MS Chellamuthu Trust and Research Foundation, KK Nagar, Madurai, India; 3University Sleep Disorders Center, College of Medicine, National Plan for Science and Technology, King Saud University, Riyadh, Saudi Arabia; 4Independent researcher, Toronto, Ontario, Canada; 5Department of Teaching and Research, Faculty of Medical Sciences, Pontificia Universidad Católica Argentina, Buenos Aires, Argentina; 6Centre for Addiction and Mental Health, University of Toronto, Toronto, Ontario, Canada; 7Center for Healthful Behavior Change (CHBC), Division of Health and Behavior, Department of Population Health, NYU Langone Medical Center, Clinical and Translational Research Institute, New York, New York, USA
Background: Sleep–wake disturbances have frequently been reported in bipolar disorder and schizophrenia, and are considered to be caused by an underlying circadian rhythm disorder. The study presented here was designed to investigate the existence of Per3 polymorphism in bipolar disorder type I (BD-I) and schizophrenic patients in South India.
Methods: Blood samples were collected from 311 BD-I patients, 293 schizophrenia patients, and 346 age- and sex-matched normal controls. Per3 genotyping was performed on DNA by polymerase chain reaction using specific primers.
Results: An increased prevalence of five repeat homozygotes was seen in BD-I patients as compared with healthy controls (odds ratio =1.72 [95% confidence interval: 1.08–2.76, P=0.02]). In BD-I patients, the frequency of the five repeat allele was higher (allele frequency =0.41), and that of the four repeat allele lower (allele frequency =0.36) (χ2=4.634; P<0.03) than in the control group. No significant association was observed in the allele frequencies of four and five repeat alleles in schizophrenia patients when compared with controls.
Conclusion: The occurrence of the five repeat allele of Per3 may be a risk factor for BD-I onset in this ethnic group.
Keywords: circadian rhythms, clock genes, Per3 polymorphism, bipolar disorder, schizophrenia
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