RESUMO
Retinoic acid (RA), the active derivative of vitamin A, is essential for normal embryonic development of vertebrates because both the lack and excess of RA result in developmental malformations. We previously reported that aryl hydrocarbon receptor (AHR) is also required for vascular and bone formation by regulating cytochrome P450 expression. However, little is known about the roles of retinoic acid receptors (RAR) and retinoid X receptors (RXR) in the embryonic development of blood vessels and molecular cross-talk between RAR/RXR and AHR. We report for the first time that RA and RAR/RXR are required for expression of AHR mRNA and the embryonic development of blood vessel and bone. The embryonic organogenesis of medaka fish was specifically inhibited by an inhibitor of RA synthesis (diethylaminobenzaldehyde), antagonists of RAR (Ro41-5253) and RXR (Ro71-4595), agonist (beta-naphthoflavone) and antagonist (alpha-naphthoflavone) of AHR, and excess RA. These reagents are useful for future studies to elucidate molecular mechanisms for vascular and bone formation in the medaka embryogenesis. Our results also show that medaka embryos may be useful for screening inhibitors of vascular formation for anti-cancer drugs.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Oryzias/embriologia , RNA Mensageiro/metabolismo , Receptores de Hidrocarboneto Arílico/metabolismo , Receptores do Ácido Retinoico/metabolismo , Tretinoína/metabolismo , Animais , Benzaldeídos/farmacologia , Vasos Sanguíneos/embriologia , Osso e Ossos/embriologia , Primers do DNA , DNA Complementar/genética , Hibridização In Situ , Modelos Biológicos , Morfogênese/efeitos dos fármacos , Oryzias/metabolismo , Receptores de Hidrocarboneto Arílico/agonistas , Receptores de Hidrocarboneto Arílico/antagonistas & inibidores , Receptores do Ácido Retinoico/antagonistas & inibidores , Receptores X de Retinoides , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/metabolismo , beta-Naftoflavona/farmacologiaRESUMO
We established three transgenic medaka fish lines overexpressing the medaka estrogen receptor under the constitutive medaka beta-actin promoter. The transgenic embryos became hypersensitive to estrogens (17 beta-estradiol and 17alpha-ethinylestradiol), and failed to develop yolk veins while blood clots formed in the blood island within 3 days after exposure to the estrogens. The embryos developed normally if exposed to estrogen after an early neurula stage, suggesting that the sensitive stage is before neurulation. The developmental defects were recovered by incubation with an anti-estrogen, tamoxifen. These results indicate that activation of estrogen receptor caused the estrogen-induced developmental defects. Our results show that the transgenic embryos can be used to assay the blood clotting activity of estrogenic compounds in vivo.
