Basdicmolecularmechanisms for tissue and organ formaiton: HH and FGF-dependent and regulation of positional information and compartment formation

在本研究中，我们以果蝇的复眼、气管、腿和内脏中胚层为模型系统，研究了其发育的基本分子机制。在复眼中，重复使用已经分化的眼小眼细胞发出的Spitz信号会触发大约10种不同类型的细胞的分化。我们的证据表明，新招募的小眼细胞对细胞命运的选择严格取决于它们的发育潜力，并且发育潜力的形成受区域特异性前置模式基因表达的控制。空间和时间调节的无呼吸信号活动对气管的发育是必不可少的。我们发现，晚期BTL的表达是无枝/呼吸信号的靶标，因此，无枝/呼吸信号包含一个正反馈环，这可能保证新的受体持续供应到生长中的气管分支细胞膜。我们还展示了HH si…的高水平更多的咬合活动对于腿部内侧区域的图案是必不可少的。在中后期的三龄迟滞盘中，高水平的HH信号抑制了pxb的转录，pxb是一种新发现的编码跨膜蛋白的基因，专门在前室表达。错误表达实验表明，Pxb可能是一种HH信号衰减剂，能够在HH-PTC相互作用之前起作用，提示腿盘中的HH信号包括一个由Pxb介导的正反馈环，运行的内脏中胚层形成环状内脏肌。已有研究表明，躯干内脏中胚层旁节段通过连接素的表达至少可分为两个区域。我们通过检测更多的内脏中胚层基因，包括hh和成纤维细胞生长因子，对此进行了扩展。外胚层HH和Wg对躯干内脏中胚层异构体靶标的表达有不同的调节作用。PS3中HH的表达似乎是正常DPP表达和胃囊形成所必需的。VMW中的无分支(FGF)被发现作为气管内脏分支的初始萌发的指南。因此，对外胚层指示信号的响应而组织的VM的同源异构体模式在以后的时间通过自我调节得以维持，这是中肠形态发生所必需的，并对气管和外胚层衍生物施加反馈作用。较少

In the present study, we examined basic molecular mechanisms of development using compound eyes, trachea, legs and visceral mesoderm in Drosophila as model systems. In compound eyes, reiterative use of Spitz signals emanating from already differentiated ommatidial cells triggers the differentiation of around ten different types of cells. We showed evidence that the choice of cell fate by newly recruited ommatidial cells strictly depends on their developmental potential and that developmental potential formation is governed by region-specific prepattern gene expression. Spatial y and temporally regulated activity of Breathless~ranchless signaling is essential for trachea development. We showed that late btl expression is a target of Branchless/Breathless signaling and hence, Branchless/Breathless signaling contains a positive feedback loop, which may guarantee a continuous supply of fresh receptors to membranes of growing tracheal branch cells. We also showed that hi g hI evels of HH si … More gnaling activity are essential for medial-region patterning in legs. In mid-to-late third instar lag discs, high levels of HH signals repress the transcription of pxb, a newly identified gene encoding as transmembrane protein expressed specifically in the anterior compartment. Misexpression experiments indicated that Pxb may serve as a HH signaling attenuator capable of acting prior to HH-Ptc interactions, suggesting tha HH signaling in leg discs includes a pxb-repression-mediated positive feedback loop, run visceral mesoderm gives rise to circular visceral muscles. It has been demonstrated that the trunk visceral mesoderm parasegment is subdivided into at least two domains by connectin expression. We extended this by examining a greater number of visceral mesodermal genes including HH and FGF. Ectodermal HH and Wg differentially regulate the expression of the metameric targets in trunck visceral mesoderm. HH expression in PS3 appeared required for normal Dpp expression and gastric caesum formation. Branchless(FGF) in Vmw as found to serve as a guide for the initial budding of tracheal visceral branches. The metameric pattern of Vm, organized in response to ectodermal instructive signals, is thus maintained at a later time via autoregu I ation, is required for midgut morphogenesis and exerts feedback effect on trachea, ectodermal derivatives. Less