title: Association of the length polymorphism in the human Per3 gene with the delayed sleep-phase syndrome: does latitude have an influence upon it?
abstract: OBJECTIVE
  The objective of this study is to analyze the influence of a previously reported hPer3 gene-length polymorphism in the delayed sleep-phase syndrome and in morningness-eveningness tendencies at low latitudes in the southern hemisphere.
  
  
  METHODS
  We have genotyped a length polymorphism in the hPer3 gene characterized by a short repeat allele (4-repeat) and a long repeat allele (5-repeat).
  
  
  METHODS
  Seventeen patients with delayed sleep-phase syndrome; 156 volunteers chosen according to Horne-Ostberg questionnaire to have morning, intermediate, or evening preference; and 110 volunteers with no Horne-Ostberg score as a sample of the general population.
  
  
  RESULTS
  We have found a higher frequency of 5-repeat allele in the delayed sleep-phase syndrome group and an association of this polymorphism with diurnal preference.
  
  
  CONCLUSIONS
  Our results suggest that latitude has a role in the influence of hPer3 gene polymorphism on delayed sleep-phase syndrome and confirm previous data showing its association with morningness-eveningness tendencies.
authors.affiliation: Department of Psychobiology/Sleep Institute, Universidade Federal de São Paulo, Brazil.
authors.forename: Danyella S
authors.initials: DS
authors.lastname: Pereira
authors.forename: Sergio
authors.initials: S
authors.lastname: Tufik
authors.forename: Fernando M
authors.initials: FM
authors.lastname: Louzada
authors.forename: Ana A
authors.initials: AA
authors.lastname: Benedito-Silva
authors.forename: Alberto R
authors.initials: AR
authors.lastname: Lopez
authors.forename: Nelson A
authors.initials: NA
authors.lastname: Lemos
authors.forename: Anna L
authors.initials: AL
authors.lastname: Korczak
authors.forename: Vania
authors.initials: V
authors.lastname: D'Almeida
authors.forename: Mario
authors.initials: M
authors.lastname: Pedrazzoli
mesh_terms: D000328:Adult; D001938:Brazil; D002940:Circadian Rhythm / Q000235:genetics; D005260:Female; D005787:Gene Frequency / Q000235:genetics; D005838:Genotype; D005843:Geography; D006801:Humans; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics*; D056950:Period Circadian Proteins; D011110:Polymorphism, Genetic / Q000235:genetics*; D012720:Severity of Illness Index; D020178:Sleep Disorders, Circadian Rhythm / Q000175:diagnosis / Q000235:genetics*; D011795:Surveys and Questionnaires; D014157:Transcription Factors
chemical_list: D009687:Nuclear Proteins; C512644:PER3 protein, human; D056950:Period Circadian Proteins; D014157:Transcription Factors