title: Exposure to valproic acid inhibits chondrogenesis and osteogenesis in mid-organogenesis mouse limbs.
abstract: In utero exposure to valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, causes neural tube, heart, and limb defects. Valpromide (VPD), the amide derivative of VPA, does not inhibit HDAC activity and is a weak teratogen in vivo. The detailed mechanism of action of VPA as a teratogen is not known. The goal of this study was to test the hypothesis that VPA disrupts regulation of the expression of genes that are critical in chondrogenesis and osteogenesis during limb development. Murine gestation day-12 embryonic forelimbs were excised and exposed to VPA or VPD in a limb bud culture system. VPA caused a significant concentration- dependent increase in limb abnormalities, which was correlated with its HDAC inhibitory effect. The signaling of both Sox9 and Runx2, key regulators of chondrogenesis, was downregulated by VPA. In contrast, VPD had little effect on limb morphology and no significant effect on HDAC activity or the expression of marker genes. Thus, VPA exposure dysregulated the expression of target genes directly involved in chondrogenesis and osteogenesis in the developing limb. Disturbances in these signaling pathways are likely to be a consequence of HDAC inhibition because VPD did not affect their expressions.
authors.affiliation: Department of Pharmacology and Therapeutics, McGill University,  Montreal, Quebec, Canada H3G 1Y6.
authors.forename: France-Hélène
authors.initials: FH
authors.lastname: Paradis
authors.forename: Barbara F
authors.initials: BF
authors.lastname: Hales
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000187:drug effects / Q000235:genetics; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D005260:Female; D005552:Forelimb / Q000166:cytology / Q000187:drug effects / Q000196:embryology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors / Q000633:toxicity*; D006655:Histone Deacetylases / Q000378:metabolism; D018878:Limb Buds / Q000166:cytology / Q000187:drug effects* / Q000196:embryology; D017880:Limb Deformities, Congenital / Q000139:chemically induced* / Q000196:embryology / Q000235:genetics; D051379:Mice; D008815:Mice, Inbred Strains; D038081:Organogenesis / Q000187:drug effects* / Q000235:genetics; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced* / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D055748:SOXB1 Transcription Factors / Q000235:genetics; D014635:Valproic Acid / Q000031:analogs & derivatives* / Q000633:toxicity
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D056572:Histone Deacetylase Inhibitors; C493716:Runx2 protein, mouse; D055748:SOXB1 Transcription Factors; C527783:Sox2 protein, mouse; D014635:Valproic Acid; D006655:Histone Deacetylases; C004651:dipropylacetamide