Association Of CLOCK、PER2、PER3 Gene Polymorphisms With Parkinson’s Disease In The Northern Chinese Han People

Objective:Parkinson’s disease is a degenerative neurological disease characterized by loss of dopaminergic neurons in nigrostriatum.It is generally believed the interaction of multiple genes and environmental factors makes the mechanism of PD extremely complicated.Epidemiology and etiology studies imply that PD has certain genetic tendency.Genetic factors in the mechanism of PD recently raise researchers’ interest.In the past,people only pay attention to motor symptoms including bradykinesia,static tremor,rigidity and postural instability.But recently more non-motor symptoms are recognized.Symptoms of circadian rhythm disorder,such as the disturbance of temperature,sleep and hormone secretion,have already been the typical symptom of neurodegenerative diseases.Daily life of PD patients can be beset by circadian rhythm disorder,such as sleep disorders,temperature disregulation and depression,which may be more severe than motor symptoms and may cause a great for the family.Recently,the clock genes that regulate circadian rhythm arouse many researchers’ interest.Circadian clock is the essence of life,commonly existing in human and other mammalians.Many physical activities of human are controlled by circadian clock,such as sleep-awake,blood pressure,heart rate,respiration,temperature,visceral activity,immunity,neuroendocrine activity,cell division and even the function of DNA.Researches have been found that single nucleotide polymorphism of clock genes was related to cardiovascular disorders,metabolic syndrome and tumor,but there is few studies concerning the relationship with neurodegenerative diseases.Studies on single nucleotide polymorphism of clock genes may provide more insights about the genetic susceptibility of PD and non-motor symptoms.Therefore,this research is to explore whether there is association between the polymorphism of clock genes(CLOCK rs1801260,PER2 rs2304672,PER3 rs228697)and susceptibility to Parkinson’ s disease in han population of Northeast of China,and the association between clock genes and biological rhythm disorders related to Parkinson’s disease is further explored.Methods:646 cases of PD(Male 316,Female 330)from consecutive outpatient andinpatient ward of our hospital were included in this study.The age of PD patients ranges from 38 to 86,with a mean of 62.21±9.83,and 352 healthy people were also included as control group.The age of control group ranges from 36 to 88,with a mean of 62.99±9.52.5~6mL of peripheral venous blood were drawn from each participant of both groups after fasting for 8-12 hours with EDTA as anticoagulant.Shift workers and long-term users for sedative drugs were all excluded from control group.The technique of Kompetitive Allele Specific PCR(KASP)was applied to determine the frequency distribution of genotype and allele gene of clock genes(CLOCK rs1801260,PER2 rs2304672,PER3rs228697)in both groups.After amplification,PCR plates were read with a Spectramax M5 FRET capable plate reader(Molecular Devices,Sunnyvale,CA,USA)using the recommended excitation and emission values.Data was then analyzed using SNPViewer software to identify SNP genotypes.The clinical information of PD group was obtained in detail,including age,gender,clinical symptom,past history,family history,education,clinical course,age of onset,medication,blood pressure and etc.Several scales for the PD group were completed face-to-face to evaluate symptoms and cognitive function,including Unified Parkinson’s Disease Rating Scale(UPDRS)and Mini-Mental State Examination(MMSE).In this study,Early-onset PD(EOPD)is defined as age of onset less than 45.The evaluation of tremor and Postural instability and gait difficulty(PIGD)was completed by using items from UPDRS-Ⅲ(items including 20,21,22,28,29).The movement symptom fluctuation of PD group was identified when the score of 32 th item from UPDRS-IV was more than 1.The depression state of PD group was identified when the score of 3rd item from UPDRS-IV was more than 1.Subjective sleep disorder of PD group was indentified when the 41 th item of UPDRS-IV was equal to 1 point.Results:1.There is significant difference in the frequency distribution of genotypes and allele genes of CLOCK rs1801260 between PD group and control group(P<0.05).The frequency of TC genotype in PD group is significantly higher than in control group(χ2=8.520,P=0.004,OR=1.818,95%CI=1.212-2.728).The frequency of CC and TC genotype in PD group is significantly higher than in control group(χ2=10.982,P=0.001,OR=1.906,95%CI=1.296-2.805).There is no significant difference in the frequency distribution of genotype and allele gene of PER2 rs2304672 and PER3 rs228697 between PD group and Control group(P>0.05).2.In PD group,there are 124 carriers and 522 non-carriers of CLOCK rs1801260 C allele gene.There is significant difference between these two groups in movement symptom fluctuation(P<0.001)and subject sleep status at night(P=0.007),and there is no significant difference in age,family history,EOPD,clinical course,stage,Hoehn-Yahr scale,UPDRS Ⅱ + Ⅲ,MMSE scale,reaction to levodopa,depression and orthostatic hypotension.3.Binary logistic regression analysis showed that movement symptom fluctuation is associated with polymorphism of CLOCK rs1801260(OR=4.474,P<0.001),UPDRS Ⅱ+Ⅲ and tremor scale.There is no significant association in levodopa treatment,age,clinical course,H-Y scale,MMSE,rigidity scale,EOPD with polymorphism of CLOCKrs1801260(P>0.05).4.Subjective sleep disorder is associated with polymorphism of CLOCK rs1801260(OR=3.998,P<0.001),UPDRS Ⅱ+Ⅲ and depression scale.There is no significant association in age,education,clinical course,stage and cognitive disorder with polymorphism of CLOCK rs1801260(P>0.05).Polymorphism of CLOCK rs1801260 can be an independent risk factor for movement symptom fluctuation and sleep disorder in Parkinson’s disease(OR=4.474,p<0.001;OR=3.998,P<0.01).5.Dyskinesia of PD is associated with polymorphism of PER2 rs2304672,UPDRSⅡ+Ⅲ and levodopa treatment,but not associated with age,education,clinical course,H-Y stage or EOPD.So polymorphism of PER2 rs2304672 can be an independent risk factor for Dyskinesia of PD(OR=4.961,p=0.035).Conclusions:Polymorphism of CLOCK rs1801260 may increase susceptibility to Parkinson’s disease in people of Northeast of China and also may be a risk factor for movement symptom fluctuation and sleep disorders in Parkinson’s disease.Polymorphism of PER2 rs2304672 and PER3 rs228697 has no association with susceptibility to Parkinson’s disease.Polymorphism of PER2 rs2304672 is associated with dyskinesia of PD,and polymorphism of PER3 rs228697 has no association with syptoms of circadian rhythm disorders in PD.