Ali Tofangchi


Research Summary:

Neurons sense and respond to the variety of mechanical inputs such as substrate stiffness and external stretch during their development and growth. I investigate the active and passive mechanical behaviors of embryonic Drosophila neurons in vivo and study the cellular mechanism underlying tension regulation and self-stretching of axon when undergoing various perturbations such as pull and push in small and large range of deformation.

Our experiments revealed that axon maintained a rest tension of a 2-12 nN in live Drosophila neurons, and behaved like a viscoelastic solid in response to fairly large (~ 50 %) and sustained stretch. However, when tension was removed neurons contracted and actively restore the tension often close to their rest tension.

In response to sustained push, neurons also showed remarkable behavior. Once axons were slackened by pushing their neuro- muscular junctions, they initially buckled but progressively contracted and became taut within ~ 5 min. This active contractile behavior persisted even when axons were pushed for three consecutive times, in that they shortened up to 40% of their original length after final push. Currently we investigate the mechanism of the active process of self-stretching and force build up in live axons.