Leah Covey
Research Mentor: Sarah Kargbo-Hill
Mentor Department: Department of Molecular, Cellular and Developmental Biology, LSA
Author(s): Leah Covey , Keyana Blake , Sarah Kargbo-Hill
Session: Session 3 (11:00 AM – 11:50 AM)
Presentation Type: Poster 5
Abstract
Amyotrophic Lateral Sclerosis (ALS) and Frontotemporal Dementia (FTD) are two devastating neurodegenerative diseases causing motor and cognitive dysfunction, respectively. Most ALS (~97%) and FTD (~45%) patients exhibit TDP-43 pathology, defined by cytoplasmic aggregates and nuclear depletion of TDP-43. TDP-43 is an RNA/DNA-binding protein essential for RNA metabolism. As a splicing repressor, when TDP-43 is depleted, repression of intronic sequences is lost, and these sequences or cryptic exons are now incorporated into 100s of transcripts. One affected gene is ATG4B (Autophagy Related 4B Cystine Peptidase), a crucial autophagy protein that forms autophagosomes. Autophagy is an essential cellular degradation pathway. Additionally, its dysfunction is linked to neurodegeneration and ALS/FTD. Thus we hypothesize that ATG4B disruptions impair autophagy, contributing to neurodegeneration. To determine which autophagy effects are attributable to ATG4B versus TDP-43 loss we knocked down TDP-43 and ATG4B using CRISPR-Cas-9 interference in human iPSC-derived glutamatergic neurons (iNeurons). To examine these downstream effects, we used western blot and qPCR. We found that TDP-43 depletion causes the inclusion of an intronic sequence between exons 10 and 11 in ATG4B mRNA, leading to a decrease in ATG4B mRNA and protein levels. Both TDP-43 knockdown and ATG4B knockdown cause a decrease in GABARAPL2, an ATG8 family protein which is critical for autophagosome maturation. This suggests a correlation between ATG4B RNA splicing and autophagy dysfunction in TDP-43 pathology. Overall, our results and future studies will provide insight into the dysregulation of autophagy in ALS/FTD and provide the foundation for potential therapeutics targeting autophagy.
