title: Epigenetic regulation of the calcitonin gene-related peptide gene in trigeminal glia.
abstract: BACKGROUND
  The neuropeptide calcitonin gene-related peptide (CGRP) plays a key role in migraine. CGRP gene expression involves an enhancer that is active in neurons, yet inactive in glia. In this report, we analyze epigenetic modifications that allow enhancer activation in glia.
  
  
  METHODS
  DNA methylation and histone acetylation states were measured in rat and human- model cell lines and primary cultures of rat trigeminal ganglia glia. The functional consequence of altering the chromatin state was determined by quantitative measurements of both calcitonin (CT) and CGRP mRNAs.
  
  
  RESULTS
  A hypermethylated CpG island flanking the enhancer was identified in glia and non-expressing cell lines. In addition, the chromatin was hypoacetylated. Treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine induced CT mRNA ~30-fold in glial cultures. Treatment with a histone deacetylase inhibitor alone had little effect; however, the combination of inhibitors yielded a synergistic ~80-fold increase in CT and ~threefold increase in CGRP mRNA. Treated glia contained CT precursor (pro-CT) immunoreactivity.
  
  
  CONCLUSIONS
  Epigenetic modulation is sufficient to induce the CGRP gene in glia. Because the CGRP gene is systemically activated by inflammatory conditions, this suggests that glial pro-CT may be an unexplored biomarker during migraine.
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Ki-Youb
authors.initials: KY
authors.lastname: Park
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Fletcher
authors.forename: Ann C
authors.initials: AC
authors.lastname: Raddant
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Russo
mesh_terms: D000818:Animals; D002116:Calcitonin / Q000096:biosynthesis / Q000235:genetics*; D015740:Calcitonin Gene-Related Peptide / Q000096:biosynthesis / Q000235:genetics; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D004742:Enhancer Elements, Genetic / Q000235:genetics; D044127:Epigenesis, Genetic; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D009457:Neuroglia / Q000378:metabolism*; D011498:Protein Precursors / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012668:Trigeminal Ganglion / Q000378:metabolism
chemical_list: D011498:Protein Precursors; D012333:RNA, Messenger; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide