RUI: Adult neurogenesis: Contributions from the innate immune system

这个项目研究了免疫系统在成人大脑中产生新细胞(神经元)中所起的作用。成年小龙虾之所以被用于这项研究，是因为产生新神经元的细胞群比通常用于这类研究的其他动物更容易研究和操作。与老鼠等其他动物的神经干细胞不同，在成人大脑中直接产生新神经元的细胞群体不会自我更新；相反，这个群体似乎得到了来自身体其他来源的细胞的补充。此前的数据表明，免疫系统为成年小龙虾大脑提供了这些前体细胞。这项建议的目标是在先前研究的基础上，明确确定免疫系统如何对成人出生的神经元的生成做出贡献。这些实验旨在检验三个假说。第一个目的是检验一种假说，即循环中的血液/免疫细胞(血细胞)与小龙虾脑中特定的物理位置(神经源性壁龛)相互作用，导致这些细胞保留并产生分化为神经元的后代。第二个目的是检验这样一种假设，即血细胞被特定的分子化学吸引到神经源性的壁龛。第三个目的是检验一种假设，即神经系统通过释放一种化学物质(5-羟色胺)来调节免疫系统神经前体的产生，这种化学物质以生物化学的方式调节免疫系统细胞的命运。通过清楚地识别这些细胞和分子的影响，这些研究将有助于了解干细胞如何使成人大脑产生新的神经元。这项工作还通过培训本科生进行干细胞研究，并教育公众了解非哺乳动物生物学研究的价值和神经系统终身可塑性的潜力，为社会做出贡献。在这个项目中，来自转基因小龙虾的绿色荧光蛋白阳性(GFP+)血细胞将被过继转移到受体非转基因动物，并将确定它们的靶器官和分化特性。此外，从转基因小龙虾免疫系统的不同区域提取的GFP+细胞将用于过继转移，以确定有能力产生成年出生神经元的细胞的组织来源。这些研究还将使用体外细胞迁移分析以及原位核酸杂交和免疫细胞化学来确定通过转录组分析确定的候选分子，从而确定将血细胞吸引到神经源性利基的局部指导线索。最后，将测试5-羟色胺激活的细胞因子(asakine 1；AST1)途径对先天性免疫系统和成人神经发生的协调调节。改变5-羟色胺水平后，将评估AST1在壁龛、脑和免疫组织中的差异表达和定位。通过测试起源于先天免疫系统的细胞产生成人出生的神经元的假设，这些研究挑战了胚胎神经组织的外胚层起源是成人大脑中神经元的唯一来源的经典观点。

This project examines the role that the immune system plays in the production of new cells (neurons) in the adult brain. Adult crayfish are used for this research because the cell populations that produce new neurons are much easier to study and manipulate than in other animals commonly used for this type of research. Unlike neural stem cells in other animals such as mice, the population of cells that directly produces new neurons in adult brains do not self-renew; rather, this population appears to be replenished by cells coming from some other source in the body. Previous data indicate that the immune system provides these precursor cells to the adult crayfish brain. The goal of this proposal is to build on this previous research to definitively identify how the immune system contributes to the generation of adult-born neurons. The experiments are designed to test three hypotheses. The first aim examines the hypothesis that circulating blood/immune cells (hemocytes) interact with specific physical locations in the crayfish brain (neurogenic niches), that cause these cells to remain and produce descendants that differentiate into neurons. The second aim examines the hypothesis that hemocytes are chemically attracted to the neurogenic niches by specific molecules. The third aim examines the hypothesis that the nervous system regulates the production of the neural precursors by the immune system via the release of a chemical (serotonin) that biochemically modulates the fate of immune system cells. By clearly identifying these cellular and molecular influences, these studies will contribute to fundamental knowledge about how stem cells enable the production of new neurons in adult brains. This work also contributes to society through training undergraduates in stem cell research, and educating the general public about the value of non-mammalian biological research and the potential for life-long plasticity in the nervous system.In this project, GFP-positive (GFP+) hemocytes originating in transgenic crayfish will be adoptively transferred to recipient non-transgenic animals, and their target organs and differentiated properties will be determined. In addition, GFP+ cells extracted from different regions of the immune system in transgenic crayfish will be used in adoptive transfers to define the tissue origins of cells that are competent to produce adult-born neurons. These studies will also identify local guidance cues that attract hemocytes to the neurogenic niche using in vitro cell migration assays, as well as in situ nucleic acid hybridization and immunocytochemistry to locate candidate molecules that have been identified by transcriptome analyses. Finally, the coordinated regulation of the innate immune system and adult neurogenesis by a 5-HT-activated cytokine (astakine 1; AST1) pathway will be tested. Differential expression and localization of AST1 in niche, brain and immune tissues will be assessed after altering 5-HT levels. By testing the hypothesis that cells originating in the innate immune system produce adult-born neurons, these studies challenge the canonical view that the ectodermal origins of embryonic neural tissues are the sole source of neurons in the adult brain.