Oral Administration of Different Forms of Exogenous Tau Protein Induces Multi-Organ Defects Across Developmental Stages in Drosophila melanogaster.

Tau is a crucial protein involved in many neurodegenerative diseases, including Alzheimer's disease. Natively, Tau is an unfolded protein found predominantly in axons that play a vital role in maintaining and stabilizing microtubules. Under pathological circumstances, Tau disengages from microtubules and forms insoluble intracellular filaments on its own, building neurofibrillary tangles in the brains of Alzheimer's patients. Although Tau exists in aggregates found in the brain and gut of Alzheimer's patients, the function of Tau in the brain is well studied, while the role of Tau in the gut needs further investigation. We have investigated the effects of Tau monomer, oligomer, and aggregates at 10 µM concentration via feeding them to the third instar larvae. To evaluate the genotoxicity, we did 4', 6-diamidino-2-phenylindole staining, while dichloro-dihydro-fluorescein diacetate staining was performed to assess cytotoxicity. Furthermore, we performed a TUNEL assay to detect apoptotic cells. Additionally, we carry out an NBT assay for biochemical estimation of reactive oxygen species by extracting hemolymph. Phenotypes were examined in different stages, i.e., larvae, pupae, and adult flies. Histological studies were performed on eye, gut tissue and reproductive organs of D. melanogaster to check the cytoskeletal alterations. The current study finds that the administration of monomer, oligomer, and aggregate forms causes genotoxicity, cytotoxicity, and cytoskeletal defects in D. melanogaster.