title: From transient transcriptome responses to disturbed neurodevelopment: role of histone acetylation and methylation as epigenetic switch between reversible and irreversible drug effects.
abstract: The superordinate principles governing the transcriptome response of differentiating cells exposed to drugs are still unclear. Often, it is assumed that toxicogenomics data reflect the immediate mode of action (MoA) of drugs. Alternatively, transcriptome changes could describe altered differentiation states as indirect consequence of drug exposure. We used here the developmental toxicants valproate and trichostatin A to address this question. Neurally differentiating human embryonic stem cells were treated for 6 days. Histone acetylation (primary MoA) increased quickly and returned to baseline after 48 h. Histone H3 lysine methylation at the promoter of the neurodevelopmental regulators PAX6 or OTX2 was increasingly altered over time. Methylation changes remained persistent and correlated with neurodevelopmental defects and with effects on PAX6 gene expression, also when the drug was washed out after 3-4 days. We hypothesized that drug exposures altering only acetylation would lead to reversible transcriptome changes (indicating MoA), and challenges that altered methylation would lead to irreversible developmental disturbances. Data from pulse-chase experiments corroborated this assumption. Short drug treatment triggered reversible transcriptome changes; longer exposure disrupted neurodevelopment. The disturbed differentiation was reflected by an altered transcriptome pattern, and the observed changes were similar when the drug was washed out during the last 48 h. We conclude that transcriptome data after prolonged chemical stress of differentiating cells mainly reflect the altered developmental stage of the model system and not the drug MoA. We suggest that brief exposures, followed by immediate analysis, are more suitable for information on immediate drug responses and the toxicity MoA.
authors.affiliation: Doerenkamp-Zbinden Chair for In Vitro Toxicology and Biomedicine, University of Konstanz, Box 657, 78457, Constance, Germany.
authors.forename: Nina V
authors.initials: NV
authors.lastname: Balmer
authors.forename: Stefanie
authors.initials: S
authors.lastname: Klima
authors.forename: Eugen
authors.initials: E
authors.lastname: Rempel
authors.forename: Violeta N
authors.initials: VN
authors.lastname: Ivanova
authors.forename: Raivo
authors.initials: R
authors.lastname: Kolde
authors.forename: Matthias K
authors.initials: MK
authors.lastname: Weng
authors.forename: Kesavan
authors.initials: K
authors.lastname: Meganathan
authors.forename: Margit
authors.initials: M
authors.lastname: Henry
authors.forename: Agapios
authors.initials: A
authors.lastname: Sachinidis
authors.forename: Michael R
authors.initials: MR
authors.lastname: Berthold
authors.forename: Jan G
authors.initials: JG
authors.lastname: Hengstler
authors.forename: Jörg
authors.initials: J
authors.lastname: Rahnenführer
authors.forename: Tanja
authors.initials: T
authors.lastname: Waldmann
authors.forename: Marcel
authors.initials: M
authors.lastname: Leist
mesh_terms: D000107:Acetylation / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D053595:Embryonic Stem Cells / Q000166:cytology*; D044127:Epigenesis, Genetic; D005136:Eye Proteins / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors / Q000008:administration & dosage / Q000633:toxicity; D006657:Histones / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D006877:Hydroxamic Acids / Q000008:administration & dosage / Q000633:toxicity*; D008745:Methylation / Q000187:drug effects; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D013997:Time Factors; D059467:Transcriptome; D014635:Valproic Acid / Q000008:administration & dosage / Q000633:toxicity*
chemical_list: D005136:Eye Proteins; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D018398:Homeodomain Proteins; D006877:Hydroxamic Acids; D000071841:PAX6 Transcription Factor; C000605730:PAX6 protein, human; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; C012589:trichostatin A; D014635:Valproic Acid