D-001 | Differential Tau expression alters AIS establishment maturation and function in murine and human neurons

Cellular and Molecular Neurobiology
Author: Cayetana Arnaiz | Email: cayetanarnaiz@gmail.com

Cayetana Arnaiz^1°, Ricardo Angelini^4°, Julieta Bianchelli^1°,  Mariana Holubiec^1°2°, Carolina Facal^3°, Indiana Páez^3°, Elena Avale^3°,  Luciana Bruno^4°, Tomás Falzone^1°2°

^1° IBioBA-MPSP-CONICET
^2° IBCN-UBA-CONICET
^3° INGEBI-CONICET
^4° IC-UBA-CONICET

The axon initial segment (AIS) regulates cargo transport and action potential initiation. Tau is developmentally regulated to express isoforms with 3 or 4 microtubules binding domains (3R/4R). Tau mutations and PTMs affect AIS plasticity, however, the molecular mechanism remains unknown. My project focuses on understanding the role of tau on transport and electrochemical activity in the AIS. Immunostainings and confocal microscopy of AnkG in hippocampal neurons from tau mouse models showed a tau-dependent establishment of the AIS. Human neurons differentiated from hiPSCs showed that modulating 3R/4R expression by transplicing is sufficient to regulate AIS presence. In addition, lysosomal transport at the AIS analyzed by live-imaging revealed differential transport dynamics after manipulating 3R/4R ratio. To determine if tau-mediated effects occur locally at the AIS, I used ExM and iPALM superresolution microscopy to study the nanoscopic localization of tau revealing a clustered distribution in axons that is different from dendrites. Chronic depolarization experiments with KCl didn’t show changes in AIS features in transgenic mice and human neurons. Spine density analysis and Ca+2 activity by live-imaging was compared in transpliced human neurons with 3R/4R disbalance. These preliminary results indicate that tau ratio alters the establishment and functional responses of the AIS such as transport and electrical activity in developing neurons.