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

项目总结/摘要 了解小生境如何调节干细胞对人类健康至关重要，因为小生境的异常调节对干细胞的影响是非常重要的。 壁龛可导致肿瘤形成或组织萎缩。在可预测的结构中， 可重复的形态发生的变化，表明生态位结构的调节和功能上的重要性。这 还没有被直接研究过。此外，确定壁龛初始定位的机制， 发展仍有待研究。为了解决这些缺陷，我们研究了果蝇后部信号中心， （PSC）-幼虫淋巴腺的生态位。PSC维持造血祖细胞，并诱导 在免疫攻击时，特异性免疫细胞的分化。PSC在胚胎发生过程中形成：其细胞 向背侧迁移，最终停留在后淋巴结处。初步数据表明 没有内脏中胚层（vm）的突变体具有分散的PSC和较少的PSC细胞。因此，总体而言， 假设是VM引导PSC定位到淋巴腺后部。我们进一步假设， 需要合并的PSC作为利基发挥最佳功能。目标1将确定虚拟机的作用及其机制 通过vm突变体的实时成像来指导PSC形成，以确定PSC的时间和类型 缺陷，然后用vm特异性RNAi敲低该线索来测试vm候选线索，接着分析vm缺陷。 PSC定位。PSC信号转导子将通过候选的PSC特异性RNAi敲低来鉴定。 传感器vm信号在附近组织中的异位表达将揭示该信号是否是真正的引导信号 是否足以指导PSC定位，或者是否赋予对其他位置线索作出反应的能力。目的2 将研究PSC聚结如何通过引起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来测试。 依赖的祖细胞，以及通过用寄生蜂攻击幼虫产生免疫应答的能力 感染，然后定量特定的免疫细胞类型。PSC可以感知生物体的营养， 免疫环境，但它是未知的，如果它感觉到反馈，从细胞调节。这将被测试， 用Gal 4/UAS驱动的细胞凋亡对淋巴腺中的祖细胞或成熟血细胞进行谱系特异性消融。 然后将测量PSC维持和分化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， 壁龛是否从其所支持的组织接收反馈。研究培训将在大学进行 在申办者、PI论文委员会和宾夕法尼亚大学教师的支持下，根据需要， 培训计划包括一个综合的和创造性的独特的指导经验序列准备 PI的职业生涯。培训包括几个机会，以提高书面和口头沟通， 专业发展活动（课程，会议，研讨会），使PI过渡到新的研究 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.