Novel Regulation of Pattern Formation in Drosophila

果蝇在实验室里很容易操纵，可以用来发现控制动物胚胎生长和形状的基因。果蝇被喂食一种会导致DNA突变的化学物质，后代被培育出来，然后检查果蝇的发育是否发生了变化。破坏必要基因的突变将导致身体模式的戏剧性变化。通过这种方式鉴定的许多苍蝇基因都与人类基因相同，它们在人类发育过程中发挥着非常相似的功能。Bejsovec实验室使用这一策略来研究苍蝇和人类共享的遗传途径的内部工作原理。这一途径由Wg/Wnt生长因子触发，告诉细胞它们在体内的什么位置以及形成什么特殊结构；成年组织中Wnt途径的不适当重新激活与人类癌症有关。Bejsovec实验室发现，已知的三个基因共同控制细胞分裂，在控制Wnt途径方面具有第二个意想不到的功能。该项目将确定这些基因如何对该途径施加控制，以及它们的行动如何扰乱苍蝇的身体计划。该项目的更广泛影响包括更深入地了解所有动物物种的发育机制，以及为Bejsovec实验室的本科生和高中生以及现有实验室课程的本科生提供实践研究体验。尽管Wg/Wnt途径在发育和组织动态平衡中起着核心作用，但从细胞表面的Wg/Wnt结合到靶基因的下游激活，这一系列事件仍然不完全清楚。风铃草(Tum)、帕瓦罗蒂(Pavarotti)和鹅卵石(Pebble)抑制培养的人细胞和果蝇胚胎中Wg/Wnt途径的活性。这些基因可能代表了一个关键的缺失环节，可能在早期对Wg/Wnt途径组件的筛选中遗漏了这一环节，因为这三个基因都在细胞分裂中具有必要的功能。在细胞质分裂中，Tum和Pav将PBL-Rhogef定位在赤道，以激活G蛋白Rho，该蛋白组织肌动蛋白收缩环。这里提出的工作将确定Tum、Pav和PBL是否(以及如何)与已知的Wg/Wnt组件联系，并将测试是否参与GTPase激活。此外，降低成体前体细胞的Tum或PBL功能会产生一种新的同源转化，这可能是细胞信号转导和细胞分裂同时中断的结果。在果蝇中可用的遗传和分子工具将被用来确定信号和/或细胞质分裂的错误调节如何改变节段身份。由此产生的数据将提供对Wg/Wnt途径控制和组织模式的洞察，并可能揭示细胞分裂和发育过程中细胞命运指定之间的新联系。改造后的苍蝇的独特外观将吸引本科生和高中生，让他们参与到科学事业中来，并有助于招募包括女性、社会经济弱势群体和代表性较低的少数族裔学生在内的多样化群体进入劳动力大军。

The fruitfly, Drosophila, is easy to manipulate in the laboratory and can be used to discover genes that control the growth and shaping of animal embryos. Flies are fed a chemical that causes mutations in the DNA, the progeny are bred and then examined for altered development of the fly. A mutation that breaks an essential gene will cause dramatic changes in the body pattern. Many of the fly genes identified this way have human counterparts, which perform very similar functions during human development. The Bejsovec laboratory uses this strategy to study the inner workings of a genetic pathway that is shared between flies and humans. This pathway, triggered by the Wg/Wnt growth factor, tells cells where they are in the body and what special structure to become; inappropriate re-activation of the Wnt pathway in adult tissues is associated with human cancers. The Bejsovec lab has found that three genes already known to work together to control cell division, have a second unexpected function in controlling the Wnt pathway. This project will determine how these genes exert control over the pathway, and how their action disrupts the fly body plan. Broader impacts of the project include deeper understanding of developmental mechanisms in all animal species, and a hands-on research experience for undergraduate and high school students in the Bejsovec laboratory and for undergraduates in an existing laboratory course. Although the Wg/Wnt pathway plays a central role in development and tissue homeostasis, the sequence of events, from Wg/Wnt binding at the cell surface to the downstream activation of target genes, is still not completely understood. Tumbleweed (Tum), Pavarotti (Pav) and Pebble (Pbl) repress Wg/Wnt pathway activity in cultured human cells and in fly embryos. These genes may represent a crucial missing link, perhaps missed in earlier screens for Wg/Wnt pathway components because all three genes have essential functions in cell division. In cytokinesis, Tum and Pav position Pbl-RhoGEF at the equator to activate the G protein, Rho, which organizes the actin contractile ring. Work proposed here will determine whether (and how) Tum, Pav, and Pbl make contact with known Wg/Wnt components, and will test whether GTPase activation is involved. In addition, reducing Tum or Pbl function in adult precursor cells creates a novel homeotic transformation which may result from the simultaneous disruption of cell signaling and cell division. Genetic and molecular tools available in Drosophila will be used to determine how misregulation of signaling and/or cytokinesis might alter segmental identity. The resulting data will provide insight into Wg/Wnt pathway control and tissue patterning, and may reveal new connections between cell division and cell fate specification during development. The unique appearance of the transformed flies will appeal to undergraduate and high school students, engaging them in the scientific enterprise and helping to recruit a diverse group, including women, socioeconomically disadvantaged and underrepresented minority students, into the workforce.