Cell to cell spreading of TDP-43 C-terminal fragments may lead to toxicity in Caenorhabditis elegans

Phoenix Toboz, Northeastern Illinois University

Cindy Voisine is the faculty sponsor of this poster.

Description

Many neurodegenerative disorders such as Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS) and prion diseases are characterized by abnormal accumulation of disease proteins in nerve cells leading to selective neurotoxicity. Moreover, a prion-like spreading mechanism might play a role in disease progression, where misfolded disease proteins spread from affected to unaffected neurons. Interestingly, ALS exhibits a focal clinical onset followed by a regional spreading of protein misfolding and cell death. Evidence points towards TAR DNA-binding protein 43 (TDP-43) as the major pathological protein in sporadic and certain familial forms of ALS where aggregates in affected neurons contain full length and fragmented forms of phosphorylated and ubiquitinated TDP-43. Despite recent advances in biomedical research on ALS disease associated proteins like TDP-43, a mechanistic explanation that links toxicity with cell to cell transmission remains unclear. To explore whether TDP-43 spreads from cell to cell, we established a C. elegans model that expresses a human TDP-43 C-terminal fragment (TDP-25) fused to red fluorescent protein in the body wall muscle cells. We employed high-resolution time-lapse imaging and observed the intercellular movement of TDP-25 from body wall muscle cells to the hypodermis, intestinal cells and gonad in living animals. These results confirm that at least certain fragments of TDP-43 are released from donor cells into neighboring receiving cells. To determine if the accumulation of TDP-43 C-terminal fragments in receiving tissues leads to toxicity, we monitored the function of the gonad. We found that accumulation of TDP-25 had no significant effect on fecundity or embryogenesis compared to wild type animals. Furthermore, expression of TDP-25 in body wall muscles did not reduce thrashing activity suggesting that the expression of TDP-43 C-terminal fragments in the body wall muscle alone does not produce a toxic phenotype. Currently, we are testing whether TDP-43 C-terminal fragments are phosphorylated, a post-translational modification associated with toxicity. Furthermore, we are mapping the movement of TDP-43 C- terminal fragments from donor cells to receiving cells using strains expressing tagged lysosomal and endosomal components. Evidence of phosphorylation and co-localization would support the model that the cell to cell spreading of toxic TDP-43 fragments contributes to the progression of disease pathology.

 
Apr 19th, 11:00 AM

Cell to cell spreading of TDP-43 C-terminal fragments may lead to toxicity in Caenorhabditis elegans

Many neurodegenerative disorders such as Alzheimer’s disease (AD), Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS) and prion diseases are characterized by abnormal accumulation of disease proteins in nerve cells leading to selective neurotoxicity. Moreover, a prion-like spreading mechanism might play a role in disease progression, where misfolded disease proteins spread from affected to unaffected neurons. Interestingly, ALS exhibits a focal clinical onset followed by a regional spreading of protein misfolding and cell death. Evidence points towards TAR DNA-binding protein 43 (TDP-43) as the major pathological protein in sporadic and certain familial forms of ALS where aggregates in affected neurons contain full length and fragmented forms of phosphorylated and ubiquitinated TDP-43. Despite recent advances in biomedical research on ALS disease associated proteins like TDP-43, a mechanistic explanation that links toxicity with cell to cell transmission remains unclear. To explore whether TDP-43 spreads from cell to cell, we established a C. elegans model that expresses a human TDP-43 C-terminal fragment (TDP-25) fused to red fluorescent protein in the body wall muscle cells. We employed high-resolution time-lapse imaging and observed the intercellular movement of TDP-25 from body wall muscle cells to the hypodermis, intestinal cells and gonad in living animals. These results confirm that at least certain fragments of TDP-43 are released from donor cells into neighboring receiving cells. To determine if the accumulation of TDP-43 C-terminal fragments in receiving tissues leads to toxicity, we monitored the function of the gonad. We found that accumulation of TDP-25 had no significant effect on fecundity or embryogenesis compared to wild type animals. Furthermore, expression of TDP-25 in body wall muscles did not reduce thrashing activity suggesting that the expression of TDP-43 C-terminal fragments in the body wall muscle alone does not produce a toxic phenotype. Currently, we are testing whether TDP-43 C-terminal fragments are phosphorylated, a post-translational modification associated with toxicity. Furthermore, we are mapping the movement of TDP-43 C- terminal fragments from donor cells to receiving cells using strains expressing tagged lysosomal and endosomal components. Evidence of phosphorylation and co-localization would support the model that the cell to cell spreading of toxic TDP-43 fragments contributes to the progression of disease pathology.