Subcategory: Cell and Molecular Biology
Room: Exhibit Hall
Bilan Yakoub - The Ohio State University
Co-Author(s): Adriana Naomi Santiago-Ruiz, University of Pennsylvania, Philadelphia, PA; Arian Arab, University of Pennsylvania, Philadelphia, Pennsylvania; Siewert Hugelier, University of Pennsylvania, Philadelphia, Pennsylvania; Charles Bond, University of Pennsylvania, Philadelphia, Pennsylvania; Melike Lakadamyali, The University of Pennsylvania, Philadelphia, Pennsylvania.
Alzheimer’s disease (AD) is a neurological disorder characterized by the accumulation of microtubule-associated protein tau into many abnormal intraneuronal aggregates detected at distinct brain regions. Their emergence strongly correlates with the progressive severity of AD diagnosed patients’ clinical symptoms and neuropathological features. These observations suggest tau aggregation plays a crucial and toxic role in AD. Tau is a monomeric highly soluble protein that maintains the assembly and stability of microtubules. Tau’s function is regulated through post-translational modifications of a specific number of residues, primarily phosphorylation. Previous studies indicate that the tau proteins that make up polymorphous insoluble tau aggregates (e.g., neurofibrillary tangles (NFTs)) have abnormal hyperphosphorylation. Based on these observations, it is suggested that ubiquitous hyperphosphorylation of tau promotes its aggregation in disease. However, the precise link between the pattern and degree of tau hyperphosphorylation with aggregation is unclear. Furthermore, how a heavily molecularly modified protein can form a wide range of morphologically diverse aggregates within one disease is not well-understood. These questions have not been investigated thoroughly due to the diffraction limit of conventional light microscopy (~250nm), in which aggregates of a size well below this limit are not resolvable. By labeling human postmortem AD brain tissues with phospho-tau antibodies that target disease relevant hyperphosphorylated residues (phospho-Thr231 (Thr231), phospho-Ser202/ phospho-Thr205 (AT8)) and super-resolution imaging, we have been able to identify tau oligomers ( 20-30 nm), linear fibrils (30-250 nm), branched fibrils (50-350 nm), and NFTs (>1μm). Moreover, by using a semi-supervised shape classification strategy, we demonstrate that each of these morphologically distinct tau aggregates have unique phosphorylation patterns. Preliminary results reveal that phospho-Ser202/phospho-Thr205 are enriched in linear fibrils, whereas phospho-Thr231 is enriched in branched fibrils. In addition, using dual-color super-resolution microscopy, we show that linear fibrils, as well as NFTs, consist of a heterogeneous distribution of hyperphosphorylated tau oligomers. Our work suggests that unique patterns and degree of tau hyperphosphorylation may lead to tau aggregate heterogeneity found in AD.
Funder Acknowledgement(s): EFRI, NSF: 220791
Faculty Advisor: Melike Lakadamyali, Melikel@pennmedicine.upenn.edu
Role: My contributions to this project consist of prepping high AD brain slices with the correct dilutions of antibodies, blocking solution and imager probes. Additionally, I had to experiment with the concentrations of antibodies and imager probes to ensure the fluorophores were not overactivated, yielding in a clean image. Lastly, I used a super resolution microscope to find regions of interest with tau aggregates and acquired numerous images on my own.