Mechanism of niche formation, and impact of niche position on tissue function

项目摘要/摘要 了解利基如何调控干细胞对人类健康至关重要，因为干细胞的异常调控 壁龛可导致肿瘤形成或组织萎缩。经过充分研究的利基市场在以下可预测的结构中形成 可复制的形态发生变化，表明生态位结构是受调控的，在功能上很重要。这 没有被直接研究过。此外，决定壁龛初始位置的机制在 发展问题仍未得到充分研究。为了解决这些缺陷，我们研究了果蝇的后部信号中心 (PSC)--幼虫淋巴腺的壁龛。PSC维持造血祖细胞，它诱导 一种特殊免疫细胞在免疫攻击时的分化。PSC在胚胎发育过程中形成：其细胞 向背部迁徙，最终栖息在淋巴腺后部。初步数据显示 没有内脏中胚层(VM)的突变体使PSC分散，PSC细胞较少。因此，总体来说 假说是Vm引导PSC定位到淋巴腺后方。我们进一步假设一个 聚合型PSC是其作为利基的最佳功能所必需的。目标1将确定VM的角色及其机制 通过对VM突变体的活体成像来识别PSC的时间和类型，从而指导PSC的形成 缺陷，然后使用特定于VM的RNAi敲击线索来测试VM候选线索，然后分析 PSC定位。PSC信号转导器将通过候选PSC特定的RNAi敲除来识别 换能器。Vm线索在附近组织中的异位表达将揭示该线索是否是真正的引导线索 足以指导PSC定位，或者它是否赋予对其他位置提示做出反应的能力。目标2 将研究PSC合并如何通过导致PSC分散来促进生态位功能，然后 评估PSC功能。分散的PSC维持祖细胞的能力将通过定量PSC- 依赖的祖细胞，以及用寄生蜂攻击幼虫产生免疫反应的能力 感染，然后量化一种特殊的免疫细胞类型。PSC可以感知生物体的营养物质和 免疫环境，但它是否感觉到来自它调节的细胞的反馈是未知的。这将通过以下方式进行测试 Gal4/UAS诱导的淋巴中祖细胞或成熟血细胞的谱系特异性消融。 然后，将测量PSC维护和区分信号的水平，以与对照进行比较。 实现这些目标将揭示生态位形成的原则，生态位结构如何影响其功能，以及 一个生态位是否从它所支持的组织那里收到反馈。研究培训将在该大学进行 根据需要，在赞助商、PI的论文委员会和宾夕法尼亚大学教职员工的建议下。 培训计划包括一系列完整的、独一无二的指导经验，以备 他们职业生涯的私人侦探。培训包括几个提高书面和口头交流的机会，以及 专业发展活动(课程、会议、研讨会)使PI过渡到一项新的研究 学术博士后奖学金的主题。

Project Summary/Abstract Understanding how niches regulate stem cells is critical to human health because aberrant regulation by the niche can cause tumor formation or tissue atrophy. Well-studied niches form in predictable structures following reproducible morphogenetic changes, suggesting niche structure is regulated and functionally important. This has not been directly studied. Additionally, the mechanisms that determine the initial positioning of niches during development remain understudied. To address these deficits, we study the Drosophila posterior signaling center (PSC)—the niche of the larval lymph gland. The PSC maintains hematopoietic progenitors, and it induces differentiation of a special immune cell upon immune challenge. The PSC forms during embryogenesis: its cells migrate dorsally, where they ultimately reside, coalesced at the lymph gland posterior. Preliminary data indicates that mutants without visceral mesoderm (vm) have dispersed PSCs and fewer PSC cells. As such, the overall hypothesis is that the vm guides PSC positioning to the lymph gland posterior. We further hypothesize that a coalesced PSC is required for its optimal function as a niche. Aim 1 will identify the role of vm and its mechanism of action in instructing PSC formation via live-imaging of vm mutants to identify the timing and type of the PSC defect, and then testing vm candidate cues with vm-specific RNAi knockdown of the cue followed by analysis of PSC positioning. The PSC signal transducer will be identified by PSC-specific RNAi knockdown of candidate transducers. Ectopic expression of the vm cue in a nearby tissue will reveal if the cue is a true guidance cue sufficient to guide PSC positioning, or whether it confers competency to respond to other positional cues. Aim 2 will investigate how PSC coalescence contributes to niche function by causing PSC dispersion and then assessing PSC functions. Ability of the dispersed PSC to maintain progenitors will be tested by quantitating PSC- dependent progenitors, and ability to generate an immune response by challenging larvae with parasitoid wasp infection, and then quantitating a specialized immune cell type. The PSC can sense the organism’s nutrient and immune environment, but it is unknown if it senses feedback from the cells it regulates. This will be tested with lineage-specific ablation of progenitors or mature hemocytes in the lymph gland with Gal4/UAS-driven apoptosis. Then the level of PSC maintenance and differentiation signals will be measured for comparison to controls. Accomplishing these aims will reveal principles of niche formation, how niche structure impacts its function, and whether a niche receives feedback from the tissue it supports. Research training will take place at the University of Pennsylvania under the advisement of the Sponsor, the PI’s thesis committee, and Penn faculty as needed. The training plan consists of an integrated and creatively unique sequence of mentorship experiences to prepare the PI for their career. Training includes several opportunities to improve written and verbal communication, and professional development activities (course, conferences, seminars) for the PI to transition to a new research topic for an academic postdoctoral fellowship.