title: Polyglutamine expansions cause decreased CRE-mediated transcription and early gene expression changes prior to cell death in an inducible cell model of Huntington's disease.
abstract: Huntington's disease (HD) is one of 10 known diseases caused by a (CAG)(n) trinucleotide repeat expansion that is translated into an abnormally long polyglutamine tract. We have developed stable inducible neuronal (PC12) cell lines that express huntingtin exon 1 with varying CAG repeat lengths under doxycycline (dox) control. The expression of expanded repeats is associated with aggregate formation, caspase-dependent cell death and decreased neurite outgrowth. Post-mitotic cells expressing mutant alleles were more prone to cell death compared with identical cycling cells. To determine early metabolic changes induced by this mutation in cell models, we studied changes in gene expression after 18 h dox induction, using Affymetrix arrays, cDNA filters and adapter-tagged competitive PCR (ATAC-PCR). At this time point there were low rates of inclusion formation, no evidence of mitochondrial compromise and no excess cell death in the lines expressing expanded compared with wild-type repeats. The expression profiles suggest novel targets for the HD mutation and were compatible with impaired cAMP response element (CRE)-mediated transcription, which we confirmed using CRE-luciferase reporter assays. Reduced CRE-mediated transcription may contribute to the loss of neurite outgrowth and cell death in polyglutamine diseases, as these phenotypes were partially rescued by treating cells with cAMP or forskolin.
authors.affiliation: Wellcome Trust Centre for Molecular Mechanisms in Disease, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Addenbrooke's Hospital, Hills Road, Cambridge CB2 2XY, UK.
authors.forename: A
authors.initials: A
authors.lastname: Wyttenbach
authors.forename: J
authors.initials: J
authors.lastname: Swartz
authors.forename: H
authors.initials: H
authors.lastname: Kita
authors.forename: T
authors.initials: T
authors.lastname: Thykjaer
authors.forename: J
authors.initials: J
authors.lastname: Carmichael
authors.forename: J
authors.initials: J
authors.lastname: Bradley
authors.forename: R
authors.initials: R
authors.lastname: Brown
authors.forename: M
authors.initials: M
authors.lastname: Maxwell
authors.forename: A
authors.initials: A
authors.lastname: Schapira
authors.forename: T F
authors.initials: TF
authors.lastname: Orntoft
authors.forename: K
authors.initials: K
authors.lastname: Kato
authors.forename: D C
authors.initials: DC
authors.lastname: Rubinsztein
mesh_terms: D000818:Animals; D016923:Cell Death; D002460:Cell Line; D003001:Cloning, Molecular; D000242:Cyclic AMP / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism; D005091:Exons; D005786:Gene Expression Regulation; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D002479:Inclusion Bodies; D008938:Mitosis; D009097:Multienzyme Complexes / Q000378:metabolism; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D016501:Neurites; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D016716:PC12 Cells; D010455:Peptides / Q000235:genetics*; D046988:Proteasome Endopeptidase Complex; D051381:Rats; D012995:Solubility; D014158:Transcription, Genetic; D019680:Trinucleotide Repeat Expansion / Q000235:genetics; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; C086055:HTT protein, human; D006360:Heat-Shock Proteins; C499524:Htt protein, rat; D000071058:Huntingtin Protein; D009097:Multienzyme Complexes; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D025801:Ubiquitin; C097188:polyglutamine; D000242:Cyclic AMP; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex