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

• Applicant: Professor Dr. Steffen Harzsch
• Subject Area: Systematics and Morphology (Zoology) ; Evolutionary Cell and Developmental Biology (Zoology)
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265461031

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.

• DFG Programme: Research Grants