RESUMO
The gene vestigial (vg) plays a key role in indirect flight muscle (IFM) development. We show here that vg is controlled by the Notch anti-myogenic signaling pathway in myoblasts and is regulated by a novel 822 bp enhancer during IFM differentiation. Interestingly, this muscle enhancer is activated in developing fibers and in a small number of myoblasts before the fusion of myoblasts with the developing muscle fibers. Moreover, we show that this enhancer is activated by Drosophila Myocyte enhancing factor 2 (MEF2), Scalloped (SD) and VG but repressed by Twist, demonstrating a sensitivity to differentiation in vivo. In vitro experiments reveal that SD can directly bind this enhancer and MEF2 can physically interact with both SD and TWI. Cumulatively, our data reveal the interplay between different myogenic factors responsible for the expression of an enhancer activated during muscle differentiation.
Assuntos
Diferenciação Celular/fisiologia , Proteínas de Drosophila/genética , Drosophila melanogaster , Elementos Facilitadores Genéticos , Regulação da Expressão Gênica no Desenvolvimento , Proteínas Nucleares/genética , Transdução de Sinais/fisiologia , Animais , Linhagem Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/anatomia & histologia , Drosophila melanogaster/embriologia , Drosophila melanogaster/genética , Voo Animal , Músculos/embriologia , Músculos/fisiologia , Mioblastos/citologia , Mioblastos/fisiologia , Fatores de Regulação Miogênica/genética , Fatores de Regulação Miogênica/metabolismo , Proteínas Nucleares/metabolismo , Receptores Notch/genética , Receptores Notch/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Proteína 1 Relacionada a Twist/genética , Proteína 1 Relacionada a Twist/metabolismoRESUMO
Myogenesis of indirect flight muscles (IFMs) in Drosophila melanogaster follows a well-defined cellular developmental scheme. During embryogenesis, a set of cells, the Adult Muscle Precursors (AMPs), are specified. These cells will become proliferating myoblasts during the larval stages which will then give rise to the adult IFMs. Although the cellular aspect of this developmental process is well studied, the molecular biology behind the different stages is still under investigation. In particular, the interactions required during the transition from proliferating myoblasts to differentiated myoblasts ready to fuse to the muscle fiber. It has been previously shown that the Notch pathway is active in proliferating myoblasts, and that this pathway is inhibited in developing muscle fibers. Furthermore, the Myocyte Enhancing Factor 2 (Mef2), Vestigial (Vg) and Scalloped (Sd) transcription factors are necessary for IFM development and that Vg is required for Notch pathway repression in differentiating fibers. Here we examine the interactions between Notch and Mef2 and mechanisms by which the Notch pathway is inhibited during differentiation. We show that Mef2 is capable of inhibiting the Notch pathway in non myogenic cells. A previous screen for Mef2 potential targets identified Delta a component of the Notch pathway. Dl is expressed in Mef2 and Sd-positive developing fibers. Our results show that Mef2 and possibly Sd regulate a Dl enhancer specifically expressed in the developing IFMs and that Mef2 is required for Dl expression in developing IFMs.