A cell-based reporter of TDP-43 disease states. Top left: In healthy cells, TDP-43 is predominantly nuclear. Within the nucleus, TDP-43 plays important roles in repressing the inclusion of cryptic exons as well as regulating its own transcript levels and isoforms. This ensures appropriate levels of functional TDP-43 within the cell. Top right: In disease, TDP-43 aggregates in the cytoplasm and is lost from the nucleus, leading to both gain-of-function and a loss-of-function. Loss of nuclear function leads to multiple detrimental events. These include DNA damage as well as the inclusion of cryptic exons in transcripts (depicted as orange boxes in the diagram), in turn leading to the production of incorrectly processed transcripts. In addition, disrupted TDP-43 autoregulation leads to unchecked accumulation of the protein’s own transcript. Bottom left: The reporter line developed by Mamede and colleagues enables the study of TDP-43 aggregation in response to stimuli—in this case exposure to TDP-43 protein aggregates that originated from patients with FTD. The reporters are composed of the C-terminal domain of TDP-43 fused to either a green or red fluorescent protein (FRET pairs). When the reporter aggregates, the proximity of TDP-43 FRET pairs enables the quantitative evaluation of aggregation within each cell. Bottom right: Protein aggregates can be quantified after excitation using a blue laser. Cells containing TDP-43 aggregates produce a FRET-positive signal that can be measured using flow cytometry whilst cells that do not have aggregates do not produce a signal. Image created in BioRender.
In some #neurodegenerative diseases, TDP-43 is both lost from the nucleus & forms clumps in the cytoplasm. These two pathologies can be challenging to model but a study in @plosbiology.org presents a new system that captures both features 🧪 Paper: plos.io/4sxw0g9 Primer: plos.io/4bvWGrw
