RESUMEN
Genetic polydactyly/arhinencephaly mouse embryo, Pdn/Pdn, exhibits suppression of Gli3 gene expression. Ochratoxin A (OTA) is a teratogen that causes neural tube defects (NTD) in mice. We investigated gender-dependent differences in the incidence of NTD induced by OTA in the Pdn/Pdn mouse. After administering 2 mg/kg OTA to Pdn/+ female mice, mated with Pdn/+ males, on day 7.5 of gestation, we examined the genotypes, sex and NTD of fetuses on day 18. Non-treated Pdn/Pdn had a 15.8% risk of NTD, and all NTD fetuses were female. When Pdn/Pdn embryos were exposed to OTA, the incidence of NTD increased to 16 (51.6%) of 31 Pdn/Pdn fetuses, and 10 (71.4%) of 14 male Pdn/Pdn fetuses exhibited NTD. From these results, it was speculated that NTD in OTA-treated male Pdn/Pdn were due to the synergistic effect between depressed Gli3 and altered sex-correlated gene expression from OTA treatment. After treatment with OTA, the embryos were recovered on day 9 and gene expressions, which were correlated with Gli3, telencephalic morphogenesis, formation of gonadal anlage, and gender-dependent differentiation were investigated. From real-time polymerase chain reaction analysis results, it was suggested that the manifestation of NTD in the male OTA-treated Pdn/Pdn might be due to the complicated altered gene expressions among Gli3, Wnt7b, Wnt8b, Fez1, Barx1, Lim1, Dmrt1, Igf1, Fog2, Dax1 and Sox9, and in particular, upregulation and gender-dependent difference in Barx1 and gender-dependent difference in Sox9 gene expressions might be noteworthy findings.
Asunto(s)
Holoprosencefalia/genética , Defectos del Tubo Neural/inducido químicamente , Ocratoxinas , Polidactilia/genética , Animales , Femenino , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Proteínas de Homeodominio/genética , Factores de Transcripción de Tipo Kruppel/genética , Masculino , Ratones , Proteínas del Tejido Nervioso/genética , Factor de Transcripción SOX9/genética , Factores Sexuales , Telencéfalo/embriología , Factores de Transcripción/genética , Proteína Gli3 con Dedos de ZincRESUMEN
The gene responsible for the polydactyly/arhinencephaly (Pdn/Pdn) mouse, which exhibits polysyndactyly and arhinencephaly and has a 13.2% risk of neural tube defects (NTD), has been identified as Gli3. Ochratoxin A (OTA) is a teratogen causing NTD in mice. When Pdn/Pdn embryos were exposed to 2 mg/kg of OTA on day 7.5, the incidence of NTD in Pdn/Pdn fetuses increased to 51.6%. Pre-treatment with folinic acid (FA), metabolically the most active form of folic acid, before OTA-treatment decreased the incidence of NTD to 20.8%. We investigated the effect of OTA and FA on gene expression in day 9 embryos using whole-mount in situ hybridization and real-time PCR. Over-expression of Fgf8 was observed at the anterior neural ridge (ANR) in the non-treated Pdn/Pdn. Over-expression at the ANR expanded in the OTA-treated Pdn/Pdn, and it was ameliorated by pretreatment with FA. Emx2 signal was observed in the dorsal forebrain in the non-treated +/+, but disappeared in the OTA-treated +/+, and was recovered by FA. The Emx2 signal was pale and the expression amount was depressed in the non-treated and OTA-treated Pdn/Pdn embryos. It was suggested that down-regulation of Gli3 induced the over-expression of Fgf8 at the ANR, that OTA treatment accelerated the over-expression, and that pretreatment with FA ameliorated the OTA-induced over-expression of Fgf8 in the Pdn/Pdn. It was also suggested that down-regulation of Gli3 induced the down-regulation of Emx2 in the Pdn/Pdn. It was further speculated that the over-expression of Fgf8 at the ANR and down-regulation of Emx2 in the dorsal forebrain may contribute to NTD induction.
Asunto(s)
Ácido Fólico/farmacología , Regulación del Desarrollo de la Expresión Génica , Holoprosencefalia/genética , Defectos del Tubo Neural/prevención & control , Ocratoxinas/toxicidad , Polidactilia/genética , Animales , Regulación hacia Abajo , Ácido Fólico/metabolismo , Genotipo , Holoprosencefalia/complicaciones , Hibridación in Situ , Ratones , Ratones Transgénicos , Modelos Genéticos , Polidactilia/complicaciones , ARN/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
It is well known that ochratoxin A (OTA) induces neural tube defects (NTDs) in mice. In the present study, OTA was administered to the genetic polydactyly/arhinencephaly mouse (Pdn/Pdn) to investigate the synergistic effect between gene and environmental toxin. OTA treatment on day 7.5 of gestation increased NTDs in the Pdn/Pdn mouse. The responsible gene for Pdn/Pdn is Gli3. So, it was speculated that specific susceptibility for OTA in the Pdn/Pdn mouse embryo may be due to the severe depression of Gli3 gene expression. As correlated genes, Gli3, Shh and Fgf8 gene expressions were examined in the Pdn mouse embryo on day 9 of gestation after administration of OTA on day 7.5. No alteration of Shh expression was observed in the non-treated Pdn/Pdn, and OTA-treated +/+ and Pdn/Pdn. Fgf8 signal was observed at the anterior neural ridge (ANR) in the non-treated +/+, and that was elongated in the non-treated Pdn/Pdn, and further elongated and more intensive in the OTA-treated Pdn/Pdn. It was suggested that Fgf8 gene expression was affected by the depression of Gli3, and alteration of Fgf8 gene expression was accelerated by the toxicity of OTA in the Pdn/Pdn.
Asunto(s)
Anomalías Múltiples/genética , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Predisposición Genética a la Enfermedad , Defectos del Tubo Neural/inducido químicamente , Ocratoxinas/toxicidad , Teratógenos/toxicidad , Animales , Femenino , Factor 8 de Crecimiento de Fibroblastos/genética , Proteínas Hedgehog , Hibridación in Situ , Factores de Transcripción de Tipo Kruppel/genética , Masculino , Ratones , Proteínas del Tejido Nervioso/genética , Defectos del Tubo Neural/genética , Polidactilia/genética , Reacción en Cadena de la Polimerasa , Embarazo , Síndrome , Transactivadores/genética , Proteína Gli3 con Dedos de ZincRESUMEN
Non-treated homozygous polydactyly/arhinencephaly (Pdn/Pdn) mouse fetuses exhibited exencephaly in 16.7% of cases. Treatment of Pdn/Pdn mice with 350 mg/kg of valproic acid (VPA) on days 8.5 and 9.5 of gestation increased the rate of exencephaly to 66.7%. The responsible gene for the Pdn mouse phenotype has been determined to be Gli3, and the suppression of Gli3 gene expression has been documented in Pdn/Pdn embryos. We investigated how the sonic hedgehog (Shh) and Fgf8 genes, the correlated genes of Gli3, are expressed in the VPA-treated exencephalic Pdn/Pdn embryos on day 10 of gestation, using whole mount in situ hybridization (WISH) and real-time PCR methods. We could not detect any alterations in Shh expression by real-time PCR, or WISH in the non-treated Pdn/Pdn and VPA-treated exencephalic Pdn/Pdn embryos. Altered Fgf8 expression patterns were observed in the commissural plate and dorsal isthmal neuroepithelium in the non-treated Pdn/Pdn embryos. We speculated that the altered expression of Fgf8 might be the result of down-regulation of Gli3 in Pdn/Pdn embryos. Fgf8 gene expression in the commissural plate and dorsal isthmal neuroepithelium exhibits wide or altered signal patterns in the VPA-treated exencephalic Pdn/Pdn embryo. From these findings, it was suggested that down-regulation of Gli3 gene expression induced the altered expression of Fgf8 in the Pdn/Pdn embryos, and that VPA treatment accelerated the alterations of Fgf8 gene expression in the Pdn/Pdn embryos. It was further speculated that altered expression of Fgf8 in the commissural plate may be the fundamental cause of exencephaly, and that the synergistic effect between gene and drug shown in this experiment may explain the differences of sensitivity in the side-effects of the drug.