Research Grant Request to Hannah's Hope Fund for Studies of Giant Axonal Neuropathy

Using skin fibroblasts from both GAN patients and the mouse gan-/- kno ckout model, we described the number and location of large aggregates of IF, typically juxtanuclear, and we noted by electron microscopy that there were numerous mitochondria associated with these aggregates. We then showed that overexpressing wild type gigaxonin resulted in the clearance of the vimentin IF (VIF) aggregates. In addition, these elevated levels of gigaxonin caused the nearly complete loss of the normal VIF network in both patient cells and in control cells. This clearance of vimentin was reversed in the presence of the proteasome inhibitor, MG-132, demonstrating the involvement of the proteasome degradation pathway. These findings are consistent with the prediction that gigaxonin is an E3 ligase adaptor protein. Importantly, we also showed that overexpressing gigaxonin results in the clearance of two of the neuronal forms of IF, peripherin and NF-L. Together these findings identify gigaxonin as a major factor involved in regulating the degradation of cytoskeletal IF, and provide an explanation for the accumulation of IF into aggregates which are the subcellular pathological hallmarks of GAN. These initial findings have led to many new questions that we are eager to answer. The answers to some of these should provide additional insights into new targets for GAN therapy. In addition, the new opportunities for collaboration resulting from Lori Sames outreach to scientists around the world now allow us to move along additional avenues of research. Our goal is to use HHF support to generate more data that will allow us to successfully compete for a co-PI NIH RO1 (i.e. a 2 investigator grant).