Investigating the morphology and branching properties of serotonergic axons

Graduate student, Melissa Hingorani, used Nanolive imaging during her thesis to interrogate the dynamic behaviour of single serotonergic axons in primary midbrain cultures (Videos 1-3). Her results, which were recently published in the scientific journal Frontiers in Neuroscience, and which can be downloaded here, “promise to produce a radically new view of the serotonergic system, both at the structural and functional levels” when combined with mathematical modelling and supercomputing simulations.

Dr. Hingorani was able to capture the dynamics of growth cones in primary midbrain cultures at various steps in the development phase between DIV 1 and DIV5. She found that growth cones detect and move along neurites using protrusions, which contact the neurite at well-defined intervals (Video 1).

When a growth cone is looking for a new attachment, these protrusions form key adhesion points with the substrate surface (Video 2). As the axon advances, it adheres and then disconnects itself from the surface on a regular basis. The high spatial and temporal resolution of our images, which were captured once every 7 seconds, allowed Dr. Hingorani to estimate both the spacing between adhesion points (2-6 μm) and the time it takes growth cones to extend the thin membrane tethers that anchor it to the surface (10 μm in ~10 mins). She was even able to capture a unique change in axon structure: the formation of a corkscrew-like morphology (Video 2; at 13 secs), which she attributes to tension forces that build up during movement.

Finally, Dr. Hingorani was able to capture two different but simultaneously occurring growth cone dynamics: one in which a growth cone moves along a neurite using protrusions and another in which a substrate is detected, and the growth cone rapidly advances along the substrate edge (Video 3). Nanolive congratulates all the authors on their impactful publication and thank them for their willingness to share their data with us. We look forward to following the next chapter of research in the Janusonis lab!