Ectopic Myf5 or MyoD prevents the neuronal differentiation program in addition to inducing skeletal muscle differentiation, in the chick neural tube.
Forced expression of the bHLH myogenic factors, Myf5 and MyoD, in various mammalian cell lines induces the full program of myogenic differentiation. However, this property has not been extensively explored in vivo. We have taken advantage of the chick model to investigate the effect of electroporation of the mouse Myf5 and MyoD genes in the embryonic neural tube. We found that misexpression of either mouse Myf5 or MyoD in the chick neural tube leads to ectopic skeletal muscle differentiation, assayed by the expression of the myosin heavy chains in the neural tube and neural crest derivatives. We also showed that the endogenous neuronal differentiation program is inhibited under the influence of either ectopic mouse Myf5 or MyoD. We used this new system to analyse, in vivo, the transcriptional regulation between the myogenic factors. We found that MyoD and Myogenin expression can be activated by ectopic mouse Myf5 or MyoD, while Myf5 expression cannot be activated either by mouse MyoD or by itself. We also analysed the transcriptional regulation between the myogenic factors and the different genes involved in myogenesis, such as Mef2c, Pax3, Paraxis, Six1, Mox1, Mox2 and FgfR4. We established the existence of an unexpected regulatory loop between MyoD and FgfR4. The consequences for myogenesis are discussed.
Delfini
Marie-Claire
MC
Biologie du Développement, UMR 7622, Université P. et M. Curie, 9 Quai Saint-Bernard, Bât. C, 6(e)E, Case 24, 75252 Paris Cedex 05, France. duprez@ccr.jussieu.fr
Duprez
Delphine
D
D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002490:Central Nervous System / Q000196:embryology*; D002642:Chick Embryo; D004268:DNA-Binding Proteins; D051379:Mice; D009124:Muscle Proteins / Q000502:physiology*; D018482:Muscle, Skeletal / Q000196:embryology*; D017570:MyoD Protein / Q000502:physiology*; D051787:Myogenic Regulatory Factor 5; D009474:Neurons / Q000502:physiology*; D017468:Receptors, Fibroblast Growth Factor / Q000502:physiology; D015534:Trans-Activators; D015854:Up-Regulation / Q000502:physiology
D004268:DNA-Binding Proteins; D009124:Muscle Proteins; C497418:Myf5 protein, mouse; D017570:MyoD Protein; D051787:Myogenic Regulatory Factor 5; D017468:Receptors, Fibroblast Growth Factor; D015534:Trans-Activators