Project Overview
Regardless of disease etiology, ~97% of ALS patients display TDP-43 pathology. TDP-43 is an RNA-binding protein that is involved in the cellular stress response. Following a stressor, TDP-43 translocates to the cytosol and is thought to be protective. However, with chronic stress and/or ALS-relevant mutations TDP-43 is depleted from the nucleus by translocating to the cytosol, where it ultimately aggregates.
For this reason, it is critical to understand the mechanisms underlying the interplay between cell stress and accumulation of pathology. The biochemical link between stress and TDP-43 pathology is unknown, but a potential mechanism is posttranslational modifications, like SUMOylation. We found that TDP-43 is SUMOylated in response to cellular stress at lysine (K) 408. Based on this, we generated a Tdp-43K408R mouse model to block native TDP-43 SUMOylation but found significant, albeit mild age-dependent phenotypes reminiscent of ALS/FTD.
We initially used aging as a stressor, but mice likely experienced low stress due to housing conditions keeping phenotypes at bay. To test if TDP-43 SUMOylation protects against an ALS-relevant stressor, I produced Tdp-43K408R; C9-BAC double mutant mice, which have a repeat expansion in the C9ORF72 gene – the greatest genetic risk factor for ALS. This mouse model does not show behavioural phenotypes. I hypothesize that these mutations will synergize, and mice will have a complement of ALS-like phenotypes; tested by behavioral, histological, biochemical and transcriptomic approaches and will test this using a complement of behavioural, histological, biochemical and transcriptomic approaches.
To examine human specific transcriptomic phenotypes, I will further explore this with hiPSC-derived motor neurons to determine whether blocking SUMOylation causes alterations in TDP-43 transcriptomic regulation, reminiscent of ALS. This work will allow for a better understanding of the mechanisms causing TDP-43 mislocalization and how this dysregulation can lead to pathogenesis ultimately leading to novel therapeutic targets.
Partners and Donors
ALS Society of Canada
