Synaptic UNC13A protein variant causes increased neurotransmission and dyskinetic movement disorder
Noa Lipstein, … , Judith J. Jans, Nils Brose
Noa Lipstein, … , Judith J. Jans, Nils Brose
Published February 13, 2017
Citation Information: J Clin Invest. 2017;127(3):1005-1018. https://doi.org/10.1172/JCI90259.
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Research Article Neuroscience

Synaptic UNC13A protein variant causes increased neurotransmission and dyskinetic movement disorder

Abstract

Munc13 proteins are essential regulators of neurotransmitter release at nerve cell synapses. They mediate the priming step that renders synaptic vesicles fusion-competent, and their genetic elimination causes a complete block of synaptic transmission. Here we have described a patient displaying a disorder characterized by a dyskinetic movement disorder, developmental delay, and autism. Using whole-exome sequencing, we have shown that this condition is associated with a rare, de novo Pro814Leu variant in the major human Munc13 paralog UNC13A (also known as Munc13-1). Electrophysiological studies in murine neuronal cultures and functional analyses in Caenorhabditis elegans revealed that the UNC13A variant causes a distinct dominant gain of function that is characterized by increased fusion propensity of synaptic vesicles, which leads to increased initial synaptic vesicle release probability and abnormal short-term synaptic plasticity. Our study underscores the critical importance of fine-tuned presynaptic control in normal brain function. Further, it adds the neuronal Munc13 proteins and the synaptic vesicle priming process that they control to the known etiological mechanisms of psychiatric and neurological synaptopathies.

Authors

Noa Lipstein, Nanda M. Verhoeven-Duif, Francesco E. Michelassi, Nathaniel Calloway, Peter M. van Hasselt, Katarzyna Pienkowska, Gijs van Haaften, Mieke M. van Haelst, Ron van Empelen, Inge Cuppen, Heleen C. van Teeseling, Annemieke M.V. Evelein, Jacob A. Vorstman, Sven Thoms, Olaf Jahn, Karen J. Duran, Glen R. Monroe, Timothy A. Ryan, Holger Taschenberger, Jeremy S. Dittman, Jeong-Seop Rhee, Gepke Visser, Judith J. Jans, Nils Brose

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Figure 4

Munc13-1P827L alters synaptic STP.

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Munc13-1P827L alters synaptic STP. (A) Example traces from autaptic hipp...
(A) Example traces from autaptic hippocampal Munc13-1 Munc13-2 DKO neurons expressing Munc13-1WT (black) or Munc13-1P827L (red) obtained during stimulation with an AP train at a frequency of 10 Hz. (B) Example traces from autaptic striatal Munc13-1 Munc13-2 DKO neurons expressing Munc13-1WT (black) or Munc13-1P827L (blue) obtained during stimulation with an AP train at a frequency of 10 Hz. (C–J) Munc13-1 Munc13-2 DKO hippocampal (left) or striatal (right) neurons expressing Munc13-1WT (black) or Munc13-1P827L (red/blue) were stimulated with AP trains at frequencies of 2.5 Hz (C and D), 5 Hz (E and F), 10 Hz (G and H), and 40 Hz (I and J), flanked by ongoing 0.2-Hz stimulation. Amplitudes were normalized to the average amplitude before the train. In I and J, the point representing the recovery of the EPSC 7 seconds after the completion of the 40-Hz train is labeled by an arrow. (K and L) Average paired-pulse ratios (defined as the ratio of the amplitudes of the second to the first EPSC of the train), recorded with different interstimulus intervals (ISIs), in Munc13-1 Munc13-2 DKO hippocampal neurons expressing Munc13-1WT (black, n = 27–37) or Munc13-1P827L (red, n = 29–36) at 22°C, 4 mM Ca2+/4 mM Mg2+ (K), or at 37°C, 2 mM Ca2+/1 mM Mg2+ (L); Mann-Whitney test. (M) Average paired-pulse ratios, recorded with different ISIs, in Munc13-1 Munc13-2 DKO striatal neurons expressing Munc13-1WT (black, n = 19–27) or Munc13-1P827L (blue, n = 18–24) at 22°C, 4 mM Ca2+/4 mM Mg2+; Mann-Whitney test. All error bars in the figure represent mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001; NS, P > 0.05. The data in C, E, G, and K were obtained from 3 independent cultures. The data in D, F, H–J, L, and M were obtained from 2 independent cultures. See Table 2 for further details.