Final Report Summary - AXONGROWTH (Systematic analysis of the molecular mechanisms underlying axon growth during development and following injury)
Axon growth potential declines during age, contributing to the lack of effective regeneration and functional recovery in the adult central nervous system. What determines the intrinsic growth potential of axons and dendrites, and how such growth is regulated during development, disease and following injury is a fundamental question in neuroscience. Although multiple lines of evidence indicate that intrinsic growth capability is genetically encoded, its nature remains poorly defined.
Neuronal remodeling of the Drosophila mushroom body offers a unique opportunity to study the mechanisms of various types of axon degeneration and growth. Our discovery that regrowth of axons following developmental pruning is not only distinct from initial outgrowth but also shares molecular similarities with regeneration following injury has been the motivation and starting point for this ambitious research plan.
In this erc supported research project, we have generated tools and methodologies that now allow us to culture whole brains ex-vivo, to dissociate brains containing WT or mutant neurons to a sparsely labeled primary culture system, and to perform CRISPR/Cas9 analyses in a tissue specific manner. Using these techniques, we found that the regrowth program is regulated by a nuclear receptor complex which functions as a ligand dependent transcription factor. Interestingly, the activity of this nuclear receptor complex is tightly regulated by levels of Nitric Oxide (NO). In fact we found that NO levels provide a switching mechanism between different growth state.
A major focus of this proposal was to make a developmental expression atlas of neurons undergoing remodeling. The results were stunning and provided us with candidate genes galore – sufficient for many more studies to come. This has led us to work on the role of actin dynamics in axon growth and branching, on adhesion and how it controls axon pathfinding and target recognition while neurons are regrowing, and on how neuron-neuron interactions mediate coordinated remodeling.
During the process of this research project, we have made important discoveries and generated key tools that are expected to significantly promote our understanding of the mechanisms controlling axon growth potential. While our work has already been published in high-impact journals, it is only the beginning of a long journey to uncover and understand how axons decide whether to grow or not during development, in disease and following injury.
Neuronal remodeling of the Drosophila mushroom body offers a unique opportunity to study the mechanisms of various types of axon degeneration and growth. Our discovery that regrowth of axons following developmental pruning is not only distinct from initial outgrowth but also shares molecular similarities with regeneration following injury has been the motivation and starting point for this ambitious research plan.
In this erc supported research project, we have generated tools and methodologies that now allow us to culture whole brains ex-vivo, to dissociate brains containing WT or mutant neurons to a sparsely labeled primary culture system, and to perform CRISPR/Cas9 analyses in a tissue specific manner. Using these techniques, we found that the regrowth program is regulated by a nuclear receptor complex which functions as a ligand dependent transcription factor. Interestingly, the activity of this nuclear receptor complex is tightly regulated by levels of Nitric Oxide (NO). In fact we found that NO levels provide a switching mechanism between different growth state.
A major focus of this proposal was to make a developmental expression atlas of neurons undergoing remodeling. The results were stunning and provided us with candidate genes galore – sufficient for many more studies to come. This has led us to work on the role of actin dynamics in axon growth and branching, on adhesion and how it controls axon pathfinding and target recognition while neurons are regrowing, and on how neuron-neuron interactions mediate coordinated remodeling.
During the process of this research project, we have made important discoveries and generated key tools that are expected to significantly promote our understanding of the mechanisms controlling axon growth potential. While our work has already been published in high-impact journals, it is only the beginning of a long journey to uncover and understand how axons decide whether to grow or not during development, in disease and following injury.