Comparative aspects of persistent neurogenesis in the central olfactory pathway of adult malacostracan crustaceans.

小龙虾大脑的中枢嗅觉通路具有持续的、终身的神经发生的特点。成人神经发生是由大脑表面产生第一代前体细胞的神经遗传生态位驱动的。这些细胞离开生态位，沿着前向和中向的迁移流向前向和中向的增殖区移动，这两者都与中央嗅觉通路有关。在它们的迁移过程中，细胞经历额外的有丝分裂并进化成第二代和第三代前体细胞。内侧增殖区产生新的局部嗅中间神经元，而外侧增殖区产生嗅投射神经元。这个系统中的细胞机制被统称为下脑增殖系统（DPS），它与哺乳动物中驱动成年神经发生的系统有很强的相似性。在这些动物中，一个神经遗传生态位，即脑室下区，产生的后代沿着吻侧迁移流向嗅球迁移，在那里神经元与现有的神经回路结合在一起。本项目旨在研究甲壳类动物嗅觉系统在广泛的比较背景和进化背景下持续神经发生的现象。我们想知道在小龙虾身上描述的成年神经发生机制是否也适用于其他甲壳类动物，并将分析可能的变化，以深入了解该系统的可能功能。通过这种比较的方法，我们将探索甲壳类动物进化的解决方案-终身神经发生。为此，我们将利用免疫组织化学技术、有丝分裂标记物组合的体内标记、脉冲追踪实验和透射电子显微镜研究10个具有代表性的Malacostraca主要分类群。具体来说，我们将分析A) DPS组件的总体布置；B)神经发生生态位超微结构；C)迁徙流的定向运动方面；D)新的嗅觉中间神经元整合到中央嗅觉通路；E)与外侧前脑半椭球体相关的持续性神经发生。这项研究将为未来的一个项目奠定基础，该项目将更深入地探索适合的甲壳类动物模型中持续神经发生的功能，特别是关于新神经元如何连接到功能性成人嗅觉系统网络的问题。

The central olfactory pathway of the crayfish brain is characterized by persistent, life-long neurogenesis. Adult neurogenesis is driven by a neurogenetic niche on the surface of the brain that generates 1st generation precursor cells. These cells leave the niche and move along an anteriorly and a medially directed migratory stream towards an anterior and a medial proliferation zone, both associated with the central olfactory pathway. During their migration, the cells undergo additional mitoses and evolve into 2nd and 3rd generation precursor cells. The medial proliferation zone contributes new local olfactory interneurons whereas the lateral proliferation zone generates olfactory projection neurons. The cellular machinery in this system that is collectively called the deutocerebral proliferative system (DPS) displays strong similarities to the system that drives adult neurogenesis in mammals. In these animals, a neurogenetic niche, the subventricular zone, generates progeny that migrate along the rostral migratory streams towards the olfactory bulb where the neurons are integrated into existing neuronal circuits. This projects sets out to examine the phenomenon of persistent neurogenesis in the crustacean olfactory system in a broad comparative context and against an evolutionary background. We want to know if the mechanisms of adult neurogenesis described for the crayfish hold for other malacostracan crustaceans too and will analyse possible variations in order to gain insights into the possible function of this system. With this comparative approach we will explore the solutions which crustaceans evolved for the task - life-long neurogenesis. To that end we will study ten representative of all major taxa of Malacostraca with immunohistochemical techniques, in vivo labelling with combinations of mitosis markers, pulse-chase experiments and transmission electron microscopy. Specifically, we will analyze A) general arrangement of the DPS components; B) ultrastructure of the neurogenetic niche; C) aspects of the directed movement in the migratory streams; D) integration of the new olfactory interneurons into the central olfactory pathway; E) persistent neurogenesis associated with the hemiellipsoid bodies in the lateral protocerebrum. This study will lay the foundations for a future project that will in more depth explore the function of persistent neurogenesis in suited model crustaceans specifically with regard to the question how the new neurons are wired up into the network of the functional, adult olfactory system.