Novel in vivo TDP-43 stress reporter models to accelerate drug development in ALS

Abstract

The development of therapies to combat neurodegenerative diseases is widely recognized as a research priority. Despite recent advances in understanding their molecular basis, there is a lack of suitable early biomarkers to test selected compounds and accelerate their translation to clinical trials. We have investigated the utility of in vivo reporters of cytoprotective pathways (e.g. NRF2, p53) as surrogate early biomarkers of the ALS degenerative disease progression. We hypothesized that cellular stress observed in a model of ALS may precede overt cellular damage and could activate our cytoprotective pathway reporters. To test this hypothesis, we generated novel ALS-reporter mice by crossing the hTDP-43tg model into our oxidative stress/inflammation (Hmox1; NRF2 pathway) and DNA damage (p21; p53 pathway) stress reporter models. Histological analysis of reporter expression in a homozygous hTDP-43tg background demonstrated a time-dependent and tissue-specific activation of the reporters in tissues directly associated with ALS, before moderate clinical signs are observed. Further work is warranted to determine the specific mechanisms by which TDP-43 accumulation leads to reporter activation and whether therapeutic intervention modulates reporters' expression. We anticipate the reporter strategy could be of great value in developing treatments for a range of degenerative disorders.

Keywords: TDP-43; in vivo; preclinical models; reporters.

Figure 1.

Demonstration of the HOTT reporter model utility to detect cellular stress associated with hTDP-43 accumulation. (a) Representative images of LacZ staining in cerebellum (upper row) or lumar spinal cord (lower row) sections from triplicated mice of indicated genotypes. PND17, post-natal day 17. Black scale bar, 40  μm. Black arrows indicate positive cells for LacZ staining. (b) Quantitation of LacZ positive area in a minimum of six images from cerebellum sections of indicated genotypes. Numbers indicate individual mice. %, positive area referred to total image area. **p < 0.005.

Figure 2.

Early detection of hTDP-43 associated stress responses using the HOTT and p21 reporter models. Representative images of LacZ staining in cerebellum and spinal cord sections of Hmox1 (upper rows) or p21 (lower rows) reporters from triplicated mice of indicated genotypes. PND15, post-natal day 15. Black scale bar, 100  μm. Black arrows indicate positive cells for LacZ staining.