title: Epigenetic Modulation of Gene Expression during Keratinocyte Differentiation.
abstract: BACKGROUND
  Epigenetic modulation of gene expression occurs by various methods, including DNA methylation and histone modification. DNA methylation of specific genes may affect the chromatin structure, preventing access by the transcriptional machinery. Although gene expression is dramatically changed during keratinocyte differentiation, there is no evidence of epigenetic modulation during the process of epidermal stratification.
  
  
  OBJECTIVE
  We investigated whether epigenetic modulation is involved in keratinocyte differentiation-specific gene regulation.
  
  
  METHODS
  We used trypsin to produce epidermal fragmentation (named T1-T4) and performed a morphological analysis using hematoxylin-eosin stain and cytokeratin expression based on reverse transcription polymerase chain reaction. We then constructed a DNA methylation microarray.
  
  
  RESULTS
  Each epidermal fragment showed morphological features of the epithelial layer. T1 represented the basal layer, T2 was the spinous layer, T3 was the granular layer, and T4 was the cornified layer. The level of the K14 proliferation marker was increased in the T1 fraction, and the level of K10 differentiation marker was increased in the T2-T4 fractions. Using a methylation microarray with the T1 and T4 fractions, we obtained many hypermethylated and hypomethylated genes from differentiated keratinocytes.
  
  
  CONCLUSIONS
  The importance of epigenetic modulation in target gene expression during keratinocyte differentiation is identified.
authors.affiliation: Department of Dermatology, Chungnam National University School of Medicine, Daejeon, Korea.
authors.forename: Seung Ju
authors.initials: SJ
authors.lastname: Back
authors.forename: Myung
authors.initials: M
authors.lastname: Im
authors.forename: Kyung Cheol
authors.initials: KC
authors.lastname: Sohn
authors.forename: Dae Kyoung
authors.initials: DK
authors.lastname: Choi
authors.forename: Ge
authors.initials: G
authors.lastname: Shi
authors.forename: Nam Ji
authors.initials: NJ
authors.lastname: Jeong
authors.forename: Young
authors.initials: Y
authors.lastname: Lee
authors.forename: Young Joon
authors.initials: YJ
authors.lastname: Seo
authors.forename: Chang Deok
authors.initials: CD
authors.lastname: Kim
authors.forename: Jeung Hoon
authors.initials: JH
authors.lastname: Lee