Critical roles of αII spectrin in brain development and epileptic encephalopathy
Yu Wang, … , Paul M. Jenkins, Jack M. Parent
Yu Wang, … , Paul M. Jenkins, Jack M. Parent
Published January 16, 2018
Citation Information: J Clin Invest. 2018;128(2):760-773. https://doi.org/10.1172/JCI95743.
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Research Article Development Neuroscience

Critical roles of αII spectrin in brain development and epileptic encephalopathy

Abstract

The nonerythrocytic α-spectrin-1 (SPTAN1) gene encodes the cytoskeletal protein αII spectrin. Mutations in SPTAN1 cause early infantile epileptic encephalopathy type 5 (EIEE5); however, the role of αII spectrin in neurodevelopment and EIEE5 pathogenesis is unknown. Prior work suggests that αII spectrin is absent in the axon initial segment (AIS) and contributes to a diffusion barrier in the distal axon. Here, we have shown that αII spectrin is expressed ubiquitously in rodent and human somatodendritic and axonal domains. CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation. Overexpression of human EIEE5 mutant SPTAN1 in embryonic rat forebrain and mouse hippocampal neurons led to similar developmental defects that were also observed in EIEE5 patient-derived neurons. Additionally, patient-derived neurons displayed aggregation of spectrin complexes. Taken together, these findings implicate αII spectrin in critical aspects of dendritic and axonal development and synaptogenesis, and support a dominant-negative mechanism of SPTAN1 mutations in EIEE5.

Authors

Yu Wang, Tuo Ji, Andrew D. Nelson, Katarzyna Glanowska, Geoffrey G. Murphy, Paul M. Jenkins, Jack M. Parent

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Figure 1

αII Spectrin expression in vitro and in vivo.

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αII Spectrin expression in vitro and in vivo. (A) αII Spectrin (red) is ...
(A) αII Spectrin (red) is ubiquitously expressed in all neuronal domains of cultured rat cortical neurons, including the axon, dendrite, and soma. Immunoreactivity is intense in dendrites marked by MAP2 (green), as well as in the axon that is negative for MAP2 staining (arrowheads). (B and C) Ankyrin-G (B) and βIV spectrin (C) (green) specifically localize to the AIS and overlap with αII spectrin. Lower-magnification images are shown in Supplemental Figure 1. (D) Western blot shows that 240-kDa αII spectrin and its 150-kDa cleavage form are expressed in both the embryonic and the postnatal rat brain, with higher expression of both forms at P10 than at E18. See complete unedited blots in the supplemental material. In the embryonic brain, αII spectrin is highly expressed in the cortical plate (CTX), with low expression in the intermediate zone (IZ) and ventricular zone (VZ). LV, lateral ventricle. At P10, αII spectrin expression is more ubiquitous. Cortex is also shown with higher magnification. Scale bars: 10 μm in A–C, 100 μm in D.