title: Alteration of the circadian clock in children with Smith-Magenis syndrome.
abstract: BACKGROUND
  Smith-Magenis syndrome (SMS) is associated with sleep disturbances and disrupted melatonin production.
  
  
  OBJECTIVE
  The study aimed to ascertain whether the sleep and melatonin production anomalies in SMS patients may be due to an alteration of the molecular mechanism of the circadian clock.
  
  
  METHODS
  Five SMS patients (3-17 yr old) and five healthy age-matched control subjects were involved in the study. Saliva and buccal scrub samples were collected every 4 h during a 24-h period. Daily profiles of melatonin were determined in saliva using a direct double-antibody radioimmunoassay. Daily profiles of clock gene mRNA levels (Per1, Per2, and Rev-erbα) were determined in buccal scrub samples by RT-PCR.
  
  
  RESULTS
  In controls, melatonin levels were elevated during the nighttime and very low during the daytime. Daily profiles of clock genes, Per1, Per2, and Rev-erbα, mRNA levels in buccal mucosa exhibited significant and mutually synchronized circadian variations (Per1 and Rev-erbα: P < 0.001; Per2: P < 0.05); the mRNA levels were elevated during the daytime and decreased during the nighttime. In SMS patients, melatonin profiles were significantly altered compared with controls, being phase reversed, phase advanced, depressed, or abolished. Only Per1 and Rev-erbα mRNA profiles exhibited significant circadian rhythms (P < 0.05); the Per2 expression exhibited high variability, and the profile was out of phase with the other clock genes.
  
  
  CONCLUSIONS
  Our findings suggest that the anomalies in melatonin profiles of SMS patients might be due to a disturbance of the molecular circadian clockwork.
authors.affiliation: Department of Neurohumoral Regulations, Institute of Physiology, Academy of Sciences of the Czech Republic, v.v.i., 14220 Prague, Czech Republic.
authors.forename: Marta
authors.initials: M
authors.lastname: Nováková
authors.forename: Sona
authors.initials: S
authors.lastname: Nevsímalová
authors.forename: Iva
authors.initials: I
authors.lastname: Príhodová
authors.forename: Martin
authors.initials: M
authors.lastname: Sládek
authors.forename: Alena
authors.initials: A
authors.lastname: Sumová
mesh_terms: D000293:Adolescent; D056926:CLOCK Proteins / Q000235:genetics / Q000378:metabolism; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D057906:Circadian Clocks / Q000235:genetics / Q000502:physiology*; D002940:Circadian Rhythm / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D008297:Male; D008550:Melatonin / Q000032:analysis / Q000378:metabolism; D012463:Saliva / Q000737:chemistry / Q000378:metabolism; D058496:Smith-Magenis Syndrome / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D056926:CLOCK Proteins; D008550:Melatonin