Project 1: Non-autonomous regulation of stem cell proliferation during regeneration

项目摘要/摘要 人体器官和组织可能会因衰老、疾病和创伤而受到不可逆转的损害，从而缩短寿命和 导致过高的医疗费用。尽管人类再生受损组织的能力有限， 一些动物具有广泛的再生能力，可以修复或完全替换受伤的肢体和 器官。成功的再生需要祖细胞对增殖的早期和显著的上调 负责产生新组织的细胞。然而，促进扩散的信号的身份，他们的 在维持和激活祖细胞内环境平衡中的作用及其调节机制 这些促再生信号在损伤反应中的表达，目前还知之甚少。淡水 扁虫是解决这些问题的理想的、易驯化的模型， 因为它的快速再生时间和可用的功能基因组学工具(例如，测序的基因组和 RNA干扰)。在有脊椎动物中，手术截肢可诱导多能体细胞的增殖。 称为新生细胞，它能在10天内完全再生受损器官，即使是在小组织中 碎片。最近，在研究肠道再生时，我们发现了一种保守的、富含肠道的 转录因子nkx2.2，出人意料地不仅需要肠道再生，而且还需要 新生细胞的增殖和其他器官的再生。随后，我们鉴定了~70个肠道- 丰富的依赖于nkx2.2的转录本，编码分泌蛋白、溶质载体、离子通道和 代谢因素，包括载脂蛋白B(ApoB)，一种脂蛋白颗粒分泌的调节剂。 基于这些观察，我们假设肠道通过非自主的方式控制再生。 Nkx2.2依赖于分泌旁分泌因子的调节和所需的转录损伤反应 新生细胞增殖。在目标1中，我们将测试载脂蛋白B是否将脂类递送到新生细胞作为 增殖和组织修复。在目标2中，我们将确定旁分泌对增殖的调节是否是动态平衡的。 或再生特异性，并确定新的新生细胞增殖调节因子。在目标3中，我们将确定 Nkx2.2是否协调肠道早期损伤反应基因表达程序。我们的长期合作 目标是了解驱动成功的组织再生的机制。我们的工作充分利用了 浮游生物独特的生物学，并将功能基因组学资源与创新的组织分离相结合 我们实验室开发的策略，以了解旁分泌信号如何控制组织修复，以及组织如何 损伤被转化为再生所需的基因表达变化。从长远来看，这些见解是 有望为改善人体器官的再生和控制失调提供途径 在癌症等人类疾病中的扩散。

PROJECT SUMMARY/ABSTRACT Human organs and tissues can be irreversibly damaged by aging, disease, and trauma, reducing lifespan and leading to exorbitant health care costs. Although humans' ability to regenerate damaged tissues is limited, some animals possess extensive regenerative capacity, and can repair or completely replace injured limbs and organs. Successful regeneration requires the early and dramatic upregulation of proliferation by progenitor cells responsible for new tissue production. However, the identities of signals that promote proliferation, their roles in homeostatic maintenance and activation of progenitor cells, and the mechanisms that modulate expression of these pro-regenerative cues in response to injury, are poorly understood. The freshwater flatworm (planarian) Schmidtea mediterranea is an ideal, tractable model in which to address these problems, because of its rapid regeneration time, and available functional genomics tools (e.g., a sequenced genome and RNA interference). In planarians, surgical amputation induces proliferation of pluripotent somatic stem cells called neoblasts, which completely regenerate damaged organs within ten days, even in small tissue fragments. Recently, while investigating intestinal regeneration, we identified a conserved, intestine-enriched transcription factor, nkx2.2, that was unexpectedly required not only for intestinal regeneration, but also for neoblast proliferation and regeneration of other organs. Subsequently, we have identified ~70 intestine- enriched, nkx2.2-dependent transcripts encoding secreted proteins, solute carriers, ion channels, and metabolic factors, including paralogs of apolipoprotein B (apoB), a regulator of lipoprotein particle secretion. Based on these observations, we hypothesize that the intestine non-autonomously controls regeneration via Nkx2.2-dependent regulation of secreted paracrine factors and transcriptional injury responses required for neoblast proliferation. In Aim 1, we will test whether ApoB delivers lipids to neoblasts as a requirement for proliferation and tissue repair. In Aim 2, we will determine if paracrine regulation of proliferation is homeostatic or regeneration-specific, and identify novel regulators of neoblast proliferation. In Aim 3, we will determine whether Nkx2.2 coordinates early injury-responsive gene expression programs in the intestine. Our long-term goal is to understand the mechanisms that drive successful tissue regeneration. Our work capitalizes on planarians' unique biology, and couples functional genomics resources with innovative tissue isolation strategies developed by our laboratory to understand how paracrine cues control tissue repair, and how tissue damage is transduced into gene expression changes required for regeneration. Long term, these insights are expected to provide avenues for improving regeneration of human organs, and for controlling dysregulated proliferation in human diseases like cancer.