title: Examination of Global Methylation and Targeted Imprinted Genes in Prader-Willi Syndrome.
abstract: BACKGROUND
  Methylation changes observed in Prader-Willi syndrome (PWS) may impact global methylation as well as regional methylation status of imprinted genes on chromosome 15 (in cis) or other imprinted obesity-related genes on other chromosomes (in trans) leading to differential effects on gene expression impacting obesity phenotype unique to (PWS).
  
  
  OBJECTIVE
  Characterize the global methylation profiles and methylation status for select imprinted genes associated with obesity phenotype in a well-characterized imprinted, obesity-related syndrome (PWS) relative to a cohort of obese and non-obese individuals.
  
  
  METHODS
  Global methylation was assayed using two methodologies: 1) enriched LINE-1 repeat sequences by EpigenDx and 2) ELISA-based immunoassay method sensitive to genomic 5-methylcytosine by Epigentek. Target gene methylation patterns at selected candidate obesity gene loci were determined using methylation-specific PCR.
  
  
  METHODS
  Study participants were recruited as part of an ongoing research program on obesity-related genomics and Prader-Willi syndrome.
  
  
  METHODS
  Individuals with non-syndromic obesity (N=26), leanness (N=26) and PWS (N=39).
  
  
  RESULTS
  A detailed characterization of the imprinting status of select target genes within the critical PWS 15q11-q13 genomic region showed enhanced cis but not trans methylation of imprinted genes. No significant differences in global methylation were found between non-syndromic obese, PWS or non-obese controls.
  
  
  METHODS
  None.
  
  
  METHODS
  Percentage methylation and the methylation index.
  
  
  CONCLUSIONS
  The methylation abnormality in PWS due to errors of genomic imprinting effects both upstream and downstream effectors in the 15q11-q13 region showing enhanced cis but not trans methylation of imprinted genes. Obesity in our subject cohorts did not appear to impact global methylation levels using the described methodology.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, University of Kansas Medical Center, 3901 Rainbow Blvd, MS 4015, Kansas City, Kansas, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Manzardo
authors.affiliation: Department of Psychiatry and Behavioral Sciences, University of Kansas Medical Center, 3901 Rainbow Blvd, MS 4015, Kansas City, Kansas, USA; Department of Pediatrics, University of Kansas Medical Center, Kansas City, Kansas, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Butler
keywords: Global DNA methylation; Imprinting center; LINE-1 methylation assay; Obesity; SNRPN