Action of valproic acid on Xenopus laevis development: teratogenic effects on eyes.
Valproic acid (VPA) is an anticonvulsive drug used in the treatment of epilepsy. Teratogenic effects of VPA have been described in different animal species. In this study, we investigate the effects of VPA on the development of Xenopus laevis embryos, by short pulse treatments (4 h) with relation to the dose and the stage of exposure to the drug. We exposed Xenopus embryos from blastula to stage 32 to three different doses of VPA (0.25, 5, and 10 mM) and we allowed these to develop until the controls reached stage 47. The embryos became more sensitive during the stages of neurulation, as observed in mouse and differently from Amblystoma, in which the more severe effects were produced by treatments at blastula stage. The malformations observed were similar to those described in mammals and other amphibians and consisted in developmental delay, perturbation of neural crest migration, and somite segmentation. We also observed abnormal development of the retina, which had never been described for VPA treatments. Therefore we analyzed the relation between VPA-induced eye malformations and the expression of Pax-6. We examined VPA-treated Xenopus embryos by whole mount in situ hybridization for mis-expression of Pax-6 in correlation with eye anomalies. Our results are consistent with the hypothesis that different members of Pax gene family are candidate target of VPA teratogenic action and in particular the decreased level of Pax-6 expression, shown by Northern blot analysis, is responsible for the retinal malformations we observed in VPA-treated Xenopus embryos. Teratogenesis Carcinog. Mutagen. 21:121-133, 2001.
Pennati
R
R
Department of Biology, University of Milano, Via Celoria 26, 20133 Milan, Italy.
Groppelli
S
S
de Bernardi
F
F
Sotgia
C
C
D000818:Animals; D000927:Anticonvulsants / Q000009:adverse effects*; D015152:Blotting, Northern; D004305:Dose-Response Relationship, Drug; D005123:Eye / Q000187:drug effects* / Q000196:embryology* / Q000378:metabolism; D005136:Eye Proteins; D005260:Female; D018398:Homeodomain Proteins / Q000096:biosynthesis; D017403:In Situ Hybridization; D008297:Male; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D012160:Retina / Q000187:drug effects / Q000196:embryology; D019170:Somites / Q000187:drug effects / Q000378:metabolism; D013723:Teratogens; D013997:Time Factors; D014635:Valproic Acid / Q000009:adverse effects*; D014982:Xenopus laevis / Q000196:embryology*
D000927:Anticonvulsants; D005136:Eye Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; D012097:Repressor Proteins; D013723:Teratogens; D014635:Valproic Acid