Regenerative and degenerative responses to axonal injury

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Project Summary/Abstract: Axons form connections between neurons over great distances in the brain and body, hence are vulnerable to damage and stress. This project studies an evolutionarily conserved stress response pathway that becomes activated in multiple scenarios of axonal damage and stress. The pathway, governed by the dileucine zipper kinase DLK, known as Wallenda (Wnd) in Drosophila, engages structural plasticity mechanisms in neurons that allow circuits to adapt to axon damage. These responses include axonal regeneration, neuronal death, and, newly discovered in this project, synapse loss. The long-term goals of this project are (1) to understand the mechanisms that lead to DLK signaling activation, and (2) to understand the cellular pathways that are regulated by DLK. The parent grant uses genetic manipulations of DLK/Wnd in mice and Drosophila, with a focus on in vivo phenotypes. However, to understand the mechanism(s) of DLK’s regulation (an overarching goal of Aim 1) and how it mediates diverse outcomes (a central goal of Aim 2), we sought to develop an in vitro paradigm for studying DLK that is amenable to biochemical, pharmacological and genetic approaches. As discussed in the April 2022 RRPR, we have now established robust methods to activate DLK signaling within primary cortical neuron cultures. The new methods provide new inroads to advancing the advancing both aims of the original grant. Pharmacology experiments are used to probe the molecular mediators of DLK signaling activation (Aim 1), and cellular imaging and biochemical experiments are used to probe how DLK activation can mediate distinct outcomes in the cultures (Aim 2). This endeavor is carried out in collaboration with Sami Barmada at the University of Michigan (UM) School of Medicine. The supplement application seeks to hire Yelitzza Aguilar, whose postbaccalaureate work on this project (in the Barmada lab at UM) will study the mechanism by which DLK mediates neuronal death in cortical neuron cultures exposed to excess glutamate. The proposed supplemental work will advance the mission of increasing diversity in biomedical research by supporting the mentorship and career development of a promising student from a disadvantaged background in biomedical research.