RESUMO
Patterning of neural crest (NC) for the formation of specific structures along the anterio-posterior (A-P) body axis is governed by a combinatorial action of Hox genes, which are expressed in the neuroepithelium at the time of NC induction. Hoxb5 was expressed in NC at both induction and migratory stages, and our previous data suggested that Hoxb5 played a role in the NC development. However, the underlying mechanisms by which Hoxb5 regulates the early NC development are largely unknown. Current study showed that both the human and mouse Foxd3 promoters were bound and trans-activated by Hoxb5 in NC-derived neuroblastoma cells. The binding of Hoxb5 to Foxd3 promoter in vivo was further confirmed in the brain and neural tube of mouse embryos. Moreover, Wnt1-Cre mediated perturbation of Hoxb5 signaling at the dorsal neural tube in mouse embryos resulted in Foxd3 down-regulation. In ovo, Foxd3 alleviated the apoptosis of neural cells induced by perturbed Hoxb5 signaling, and Hoxb5 induced ectopic Foxd3 expression in the chick neural tube. This study demonstrated that Hoxb5 (an A-P patterning gene) regulated the NC development by directly inducing Foxd3 (a NC specifier and survival gene).
Assuntos
Fatores de Transcrição Forkhead/genética , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio/genética , Crista Neural/metabolismo , Proteínas Repressoras/genética , Animais , Apoptose/genética , Sequência de Bases , Padronização Corporal/genética , Embrião de Galinha , Fatores de Transcrição Forkhead/metabolismo , Proteínas de Homeodomínio/metabolismo , Humanos , Hibridização In Situ , Camundongos Endogâmicos ICR , Camundongos Transgênicos , Microscopia de Fluorescência , Dados de Sequência Molecular , Crista Neural/embriologia , Tubo Neural/embriologia , Tubo Neural/metabolismo , Regiões Promotoras Genéticas/genética , Ligação Proteica , Proteínas Repressoras/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência do Ácido Nucleico , Transdução de Sinais/genética , Proteína Wnt1/genética , Proteína Wnt1/metabolismoRESUMO
To establish a genetic tool for conditional deletion or expression of gene in neurons in a temporally controlled manner, we generated a transgenic mouse (NSE-MerCreMer), which expressed a tamoxifen inducible type of Cre recombinase specifically in neurons. The tamoxifen inducible Cre recombinase (MerCreMer) is a fusion protein containing Cre recombinase with two modified estrogen receptor ligand binding domains at both ends, and is driven by the neural-specific rat neural specific enolase (NSE) promoter. A total of two transgenic lines were established, and expression of MerCreMer in neurons of the central and enteric nervous systems was confirmed. Transcript of MerCreMer was detected in several non-neural tissues such as heart, liver, and kidney in these lines. In the background of the Cre reporter mouse strain Rosa26R, Cre recombinase activity was inducible in neurons of adult NSE-MerCreMer mice treated with tamoxifen by intragastric gavage, but not in those fed with corn oil only. We conclude that NSE-MerCreMer lines will be useful for studying gene functions in neurons for the conditions that Cre-mediated recombination resulting in embryonic lethality, which precludes investigation of gene functions in neurons through later stages of development and in adult.
