| The development of organs depends on cell-to-cell communication for the establishment of cell adhesion and control of organ growth. Several signaling pathways are involved and contributed to the transcription regulation of genes. Wingless(Wg) and Hedgehog(Hh) signaling pathways play a vital role in wing development. However, the upstream regulatory factors and the mechanism by which the signaling pathways are integrated and coordinated remain unclear.Drosophila adult wing is developed from the wing disc at the larval stage. The growth and patterning of the wing disc relies on the establishment of two signaling centers. One center is established at the anterior-posterior(A/P) boundary by the activity of Hh, another center is established at the dorsal-ventral(DV) boundary by the activity of Wg.Thus, Drosophila wing disc is an ideal model to investigate organ development and gene regulatory network.We focus on a transcription factor, Midline(Mid), which is Drosophila homolog of Tbx20 in vertebrates. As an evolutionarily conserved transcription factor of T-box family, Mid plays a vital role in cell fate specification and tissue morphogenesis during a series of developmental processes.Here, we show that the transcription factor Mid is expressed in the wing disc of Drosophila and plays a vital role in wing development. Loss or knock down of the Mid function in the wing disc induced hyper-expression of wg and yielded cocked and non-flat wings. We also observed a wider space between vein 3 and vein 4 and ectopic wing hairs. Overexpression of Mid in the wing disc markedly repressed the expression of wg, DE-Cadherin(DE-Cad) and armadillo(arm), and resulted in a small and blistered wing. In addition, a reduction in the dose of mid enhanced phenotypes of a gain-of-function mutant of hh. We also observed repression of hh upon overexpression of Mid in the wing disc. Taken together, we propose that Mid regulates wing development by repressing wg and hh in Drosophila. |
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