![]() ![]() The AMG consists of visceral muscle and an epithelial tube. These results are the first demonstration that Wnt signaling contributes to LR asymmetric development in invertebrates, as it does in vertebrates. arrow ( arr), an ortholog of the mammalian gene encoding low-density lipoprotein receptor-related protein 5/6, which is a co-receptor of the Wnt-signaling pathway, was also essential for LR asymmetric development of the AMG. frizzled 2 ( fz2) and Wnt4, which encode a receptor and ligand of Wnt signaling, respectively, were required for the LR asymmetric development of the AMG. In this study, we found that genes encoding components of the Wnt-signaling pathway are required for LR asymmetric development of the anterior part of the embryonic midgut (AMG). Drosophila has several organs that show directional and stereotypic LR asymmetry, including the embryonic gut, which is the first organ to develop LR asymmetry during Drosophila development. Therefore, we studied the genetic pathway of LR asymmetric development in Drosophila. The mechanisms of LR asymmetric development are evolutionarily divergent, and are poorly understood in invertebrates. Many animals develop left–right (LR) asymmetry in their internal organs. The distribution of enhancer elements and their control of TmI gene expression are similar to those regulating transcription of the muscle promoter of the TmII gene and provide a framework for the coordinate expression of the two genes. We propose a model in which transcriptional regulation of the Drosophila TmI gene is controlled by the cooperative interaction of multiple positive and negative cis-acting regulatory elements that control the temporal and muscle-type pattern of expression. We also show that this somatic/visceral muscle element(s) can be repressed through an adjacent negative control region, suggesting that the regulation of expression in these muscles is under dual control during both phases of myogenesis. Dissection of this enhancer region into smaller fragments has allowed us to identify a 91-bp enhancer fragment sufficient for directing expression in all somatic and visceral muscles of the larva and adult but not in the indirect flight muscles and tergal depressor of the trochanter or jump muscles of the adult. One of these enhancers is contained within a 355-bp fragment that is sufficient to direct high levels of temporally regulated expression from a heterologous promoter in all muscles of transgenic flies. Leah sabacan full#Together these enhancer regions contain multiple muscle-type-specific positive and negative cis-acting elements which together contribute toward full expression of the gene. We show here that transcriptional regulation of the Drosophila tropomyosin I ( TmI) gene during myogenesis is under the control of at least two muscle enhancer regions located within the first intron of the gene. Muscle development involves the coordinated regulation of transcription of muscle-type-specific genes and their encoded proteins during myogenesis. ![]()
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