Expression of a Fragment of Ankyrin 2 Disrupts the Structure of the Axon Initial Segment and Causes Axonal Degeneration in Drosophila

  • Joshua Spurrier
  • Arvind K. Shukla
  • Tyler Buckley
  • Svetlana Smith-Trunova
  • Irina Kuzina
  • Qun Gu
  • Edward GinigerEmail author


Neurodegenerative stimuli are often associated with perturbation of the axon initial segment (AIS), but it remains unclear whether AIS disruption is causative for neurodegeneration or is a downstream step in disease progression. Here, we demonstrate that either of two separate, genetically parallel pathways that disrupt the AIS induce axonal degeneration and loss of neurons in the central brain of Drosophila. Expression of a portion of the C-terminal tail of the Ank2-L isoform of Ankyrin severely shortens the AIS in Drosophila mushroom body (MB) neurons, and this shortening occurs through a mechanism that is genetically separate from the previously described Cdk5α-dependent pathway of AIS regulation. Further, either manipulation triggers morphological degeneration of MB axons and is accompanied by neuron loss. Taken together, our results are consistent with the hypothesis that disruption of the AIS is causally related to degeneration of fly central brain neurons, and we suggest that similar mechanisms may contribute to neurodegeneration in mammals.


Axon initial segment Axonal degeneration Neurodegeneration Ankyrin 2 Cdk5 Drosophila 



We thank each member of our lab, and also Chi-Hon Lee and Ela Serpe, for helpful discussions during the course of this work. We thank Jan Pielage, Chi-Hon Lee, Andreas Prokop, Melissa Rolls, and the Bloomington Drosophila Stock Center for fly stocks used in these experiments. We are grateful to Stephen Wincovitch of the NHGRI Cytogenetics and Microscopy Core Facility for his assistance with microscopy.

Funding Information

These experiments were supported by the Basic Neuroscience Program of the Intramural Research Program of the National Institute of Neurological Disorders and Stroke, National Institutes of Health, Z01 NS003106.

Supplementary material

12035_2019_1477_Fig6_ESM.png (717 kb)
Supplemental Fig. 1

Ank2 constructs localize to soma, dendrites, and axons of MB neurons. Overexpression of the VENUS-tagged Ank2 fragments. Z-projected confocal images of late third-instar larval brains. All scale bars are equal to 20μm. MB-specific GAL4 driver 201Y is present in all samples. (a, b, c) Dorsal view of MB, illustrating expression in calyx (dendrites) and axonal lobes. (d, e, f) Posterior view of MB, revealing expression in the cell bodies. (a,d) UAS-VENUS-Ank2-S (U-A2S), (b,e) UAS-VENUS-Ank2-L4 (U-A2L4), and (c,f) UAS-VENUS-Ank2-L8 (U-A2L8) (PNG 717 kb)

12035_2019_1477_MOESM1_ESM.tif (538 kb)
High resolution image (TIF 537 kb)


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Copyright information

© This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2019

Authors and Affiliations

  1. 1.National Institute of Neurological Disorders and Stroke, National Institutes of HealthBethesdaUSA
  2. 2.Cellular Neuroscience, Neurodegeneration and Repair Program, Department of NeurologyYale University School of MedicineNew HavenUSA
  3. 3.The Scripps Research InstituteSan DiegoUSA
  4. 4.Walter Reed National Military Medical CenterBethesdaUSA

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