RESUMEN
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).
Asunto(s)
Factores de Transcripción Forkhead/genética , Regulación del Desarrollo de la Expresión Génica , Proteínas de Homeodominio/genética , Cresta Neural/metabolismo , Proteínas Represoras/genética , Animales , Apoptosis/genética , Secuencia de Bases , Tipificación del Cuerpo/genética , Embrión de Pollo , Factores de Transcripción Forkhead/metabolismo , Proteínas de Homeodominio/metabolismo , Humanos , Hibridación in Situ , Ratones Endogámicos ICR , Ratones Transgénicos , Microscopía Fluorescente , Datos de Secuencia Molecular , Cresta Neural/embriología , Tubo Neural/embriología , Tubo Neural/metabolismo , Regiones Promotoras Genéticas/genética , Unión Proteica , Proteínas Represoras/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de Ácido Nucleico , Transducción de Señal/genética , Proteína Wnt1/genética , Proteína Wnt1/metabolismoRESUMEN
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.