Dissecting neuroinflammatory mechanisms in a model of progressive TDP-43 pathology

Project Summary/Abstract Neuroinflammation, where immune cell overactivation can lead to catastrophic destruction of otherwise healthy neuronal tissue, is a critical pathological feature of both Alzheimer’s Disease (AD) and Amyotrophic Lateral Sclerosis (ALS). Dissecting the pathways leading to pathological neuroinflammation and defining precise immunomodulatory targets has the potential to greatly enhance therapeutic options for those suffering from neurodegenerative diseases. 97% of ALS patients and 57% of AD patients present with dysregulation of the RNA-binding protein TDP-43 in neurons, leading to disrupted RNA splicing of a variety of critical genes. Our bioinformatic analysis has identified 23 genes commonly dysregulated by TDP-43 pathology in multiple independent human studies; among these is STMN2, which we have characterized as a regulator of NMJ function and stability, and ATP8A2, which has never been studied in the context of AD or ALS, yet is an extremely attractive target for studying neuroinflammation. ATP8A2 is a phosphatidylserine (PS) flippase that regulates PS exposure onto the extracellular leaflet of the plasma membrane, where it acts as the cellular “eat me” signal for immune cell activation and phagocytosis. Aberrantly exposed PS can occur via flippase dysfunction, which is sufficient to cause neuronal phagocytosis by neuroimmune cells. Humans with ATP8A2 mutations have severe neurological dysfunction and ATP8A2 mutant mice develop axon degeneration, implicating ATP8A2 as a primary regulator of neuroinflammation and axon loss, downstream of impaired TDP-43. Excitingly, we have found that ATP8A2/STMN2 double heterozygote mice display a progressive decrease in motor strength that is significantly different from either single heterozygote, demonstrating the utility of this model for investigating TDP-43 pathology. This project will determine the genetic and cellular regulators of PS exposure and neuroimmune cell activation, and test the degree to which ATP8A2 deficiency exacerbates the neurodegenerative phenotypes (e.g. STMN2-mediated NMJ defects) observed in TDP-43 pathology. If successful, this project will characterize the fundamental mechanisms of neuron/immune cell interactions, and define potential therapeutic targets against neuroinflammation in AD or ALS. This project will occur at Washington University in St. Louis, a premier institute for biomedical research, under the guidance of Aaron DiAntonio, who has become a leader in the field of axon degeneration over the past two decades. The DiAntonio Lab’s record of success accentuates the resources and equipment available to perform outstanding science, including two state-of-the-art tissue culture rooms, multiple automated cell imagers and confocal microscopes, and access to a world-class mouse facility. Additionally, the extraordinary neuroscience and immunology communities at Washington University provide excellent opportunities to facilitate the growth and transition from trainee to independent investigator, which will occur through the classes, lectures, journal clubs, retreats, and symposia offered by the institution.