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Presynaptic α2δ-3 is required for synaptic morphogenesis independent of its Ca2+-channel functions

Nature Neuroscience volume 12, pages 1415–1423 (2009)Cite this article

Abstract

Synaptogenesis involves the transformation of a growth cone into synaptic boutons specialized for transmitter release. In Drosophila embryos lacking the α2δ-3 subunit of presynaptic, voltage-dependent Ca2+ channels, we found that motor neuron terminals failed to develop synaptic boutons and cytoskeletal abnormalities arose, including the loss of ankyrin2. Nevertheless, functional presynaptic specializations were present and apposed to clusters of postsynaptic glutamate receptors. The α2δ-3 protein has been thought to function strictly as an auxiliary subunit of the Ca2+ channel, but the phenotype of α2δ-3 (also known as stj) mutations cannot be explained by a channel defect; embryos lacking the pore-forming α1 subunit cacophony formed boutons. The synaptogenic function of α2δ-3 required only the α2 peptide, whose expression sufficed to rescue bouton formation. Our results indicate that α2δ proteins have functions that are independent of their roles in the biophysics and localization of Ca2+ channels and that synaptic architecture depends on these functions.

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Figure 1: α2δ-3 null embryos have a defect in bouton morphogenesis.
Figure 2: α2δ-3 null NMJs exhibit an arrest of synaptic morphogenesis.
Figure 3: Ankyrin2-XL is absent at the α2δ-3 null NMJ.
Figure 4: α2δ-3 null embryos retain synaptic components at their terminals.
Figure 5: Ca2+ channel α1 subunits are not detectable in α2δ-3 null embryonic active zones.
Figure 6: α2δ-3 null embryos have spontaneous minis, but no evoked synaptic transmission.
Figure 7: Bouton formation does not require the δ subunit.
Figure 8: Bouton formation does not require the cac α1 subunit.

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Acknowledgements

We thank H. Kazama for assistance with the electrophysiology, R. Ordway, J.T. Littleton, L. Hall, H. Aberle, K. Basler and the Bloomington Stock Center for stocks and reagents, D. Featherstone, T. Littleton, N. Reese and A. Goldstein for helpful discussions, L. Bu and M. Liana of the MRDDRC Imaging and Histology Cores, the Harvard Medical School electron microscopy facility, and E. Pogoda for assistance. This work was supported by US National Institutes of Health grants RO1 NS041062 and MH075058 (T.L.S.) and a National Defense Science and Engineering Graduate Fellowship (P.T.K.).

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  1. F.M. Kirby Neurobiology Center, Children's Hospital Boston, Boston, Massachusetts, USA

    Peri T Kurshan, Asli Oztan & Thomas L Schwarz

  2. Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA

    Peri T Kurshan, Asli Oztan & Thomas L Schwarz

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Contributions

P.T.K. performed the experiments. A.O. designed and generated the HA-tagged α2δ-3 construct, collaborated in the design of experiments involving that construct and assisted with manuscript editing. P.T.K. and T.L.S. designed the experiments and wrote the paper.

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Correspondence to Thomas L Schwarz.

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Kurshan, P., Oztan, A. & Schwarz, T. Presynaptic α2δ-3 is required for synaptic morphogenesis independent of its Ca2+-channel functions. Nat Neurosci 12, 1415–1423 (2009). https://doi.org/10.1038/nn.2417

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