Calcium and Microtubule Activity After Explosive Injury in Drosophila

Open Access
Author:
Tamminga, Mila Anne
Area of Honors:
Biochemistry and Molecular Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Melissa Rolls, Thesis Supervisor
  • Sarah Ellen Ades, Honors Advisor
Keywords:
  • Drosophila
  • Neurons
  • Neuronal injury
  • Model system organism
  • Microtubules
  • Calcium
Abstract:
Neurons must last an entire lifetime, despite facing frequent risk of injury and stress from sources such as traumatic brain injury. Laser injury in Drosophila has long been used as a model to understand the axon injury response, typically by using a laser to sever neurites1. However, I recently observed an alternate type of axon injury, termed explosive injury, which produces an immediate, obviously distinct phenotype. In this thesis, I characterize the cellular response to explosive neuron injury in order to establish a basis for further research concerning downstream effects and regeneration. I compared microtubule activity after explosive and controlled injury in control and bsk dominant negative background and found that explosive injury causes immediate, global changes in microtubule dynamics independent of the JNK signaling pathway. GCaMP fluorescent calcium imaging was used to identify the source, scope, and duration of calcium elevation after injury. I found that explosive injury causes an immediate 4-fold spike in cytosolic calcium levels that lasts up to eight hours. A genetically encoded voltage indicator was used to verify that the calcium spike is connected to neuron depolarization and voltage change after explosive injury. Overexpressing the potassium channel Kir2.1 to suppress depolarization was found to prevent both calcium spike and microtubule activity upregulation. This leads me to propose a possible mediating role for calcium in controlling microtubule response after explosive injury. Overall, this thesis sets a foundation for future work using explosive injury as an alternative model of traumatic nervous system injuries.