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Hypocretin (orexin) neuropeptide precursor gene, HCRT, polymorphisms in early-onset narcolepsy with cataplexy

Xiao Song Dong1, Su Fang Ma, Chun Wei Cao

  • 1Department of Pulmonary Medicine, Beijing University People's Hospital, Beijing, China.

Sleep Medicine
|May 7, 2013
PubMed

Insights

Genetic analysis of the hypocretin (orexin) precursor gene (HCRT) in children with narcolepsy identified novel mutations. Two specific HCRT gene mutations were found only in affected children but are unlikely to cause functional changes.

Area of Science:

  • Genetics
  • Neuroscience
  • Sleep Medicine

Background:

  • Narcolepsy with cataplexy is a rare neurological disorder.
  • The hypocretin (orexin) system is implicated in sleep-wake regulation.
  • Genetic factors may contribute to early-onset narcolepsy.

Purpose of the Study:

  • To investigate mutations in the hypocretin (orexin) neuropeptide precursor (HCRT) gene in young children with narcolepsy and cataplexy.
  • To determine if HCRT gene variations are associated with the development of early-onset narcolepsy.

Main Methods:

  • Sequencing of the entire HCRT gene and its promoter region in 181 patients and 153 controls.
  • Further sequencing of exon 2, containing identified nonsynonymous changes, in an additional 298 early-onset subjects and 148 controls.
  • Analysis of single nucleotide polymorphisms (SNPs) and their segregation in affected families.

Main Results:

  • Nine rare novel polymorphisms and one common polymorphism (rs760282) were identified in HCRT, with no significant differences between patients and controls.
  • Two novel nonsynonymous substitutions in exon 2 (+977 H54A, +979 G55R) were found exclusively in two patients with early-onset narcolepsy.
  • A third substitution (+1019 K68R) was found in both patients and controls, with segregation observed from unaffected parents to offspring for two of the three nonsynonymous SNPs.

Conclusions:

  • Novel nonsynonymous substitutions in the HCRT gene were identified in patients with early-onset narcolepsy.
  • Two of these substitutions were specific to narcolepsy patients but are unlikely to be functionally significant.
  • The study suggests that these specific HCRT mutations may not be the primary cause of narcolepsy with cataplexy in young children, especially in heterozygous individuals.
Abstract

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