Valproic acid-induced alterations in growth and neurotrophic factor gene expression in murine embryos

Although the teratogenicity of valproic acid (VPA) has been well establishe d, the mechanism(s) by which this anticonvulsant drug induces malformations remains controversial. Using the combined molecular techniques of in situ- transcription (IST) and antisense RNA (aRNA) amplification we analyzed VPA- induced alterations in the gene expression for 10 genes within the neural t ubes of embryos from two murine strains that have been shown to differ in t heir susceptibility to VPA-induce neural tube defects (NTD). Pregnant dams from both SWV (susceptible) and LM/Bc (resistant) strains were either treat ed with saline (control) or VPA (600 mg/kg) on gestational day (GD) 8:12 (d ay:hour). Neural tubes were isolated from control or VPA exposed embryos at three gestational time points, which represented the beginning (GD 8:18), middle (GD 9:00), and end (GD 9:12) of neural tube closure (NTC) in both of these murine strains. Using univariant statistics we demonstrated that in LM/Bc embryos with NTDs, the expression of bdnf, ngf; and trk, ngf-R were s ignificantly elevated at all three time points, and the cytokine, cntf was significantly decreased at GD 9.00. In contrast, the major gene alterations observed in SWV embryos were a significant increase in tfg alpha: and tgf beta 1-3 at GD 9.00. In an effort to better define the more intricate inter actions between VPA exposure and the expression of these genes, we analyzed our data using Principal Component Analysis. The results from this analysi s demonstrated that embryos from these two stains behaved differently, not only in response to a VPA exposure, but also under control conditions, whic h may explain the multifactorial nature of NTDs in these mice. (C) 2000 Pub lished by Elsevier Science Inc. All rights reserved.