• Tomohiro Ohgomori, Ryo Yamasaki, Hideyuki Takeuchi, Kenji Kadomatsu, Jun-Ichi Kira, and Shozo Jinno.
• Department of Anatomy and Neuroscience, Graduate School of Medical Science, Kyushu University, Fukuoka 812-8582, Japan.
• Neuroscience. 2017 Jul 25; 356: 114-124.

AbstractFrom a view point of the glutamate excitotoxicity theory, several studies have suggested that abnormal glutamate homeostasis via dysfunction of glial glutamate transporter-1 (GLT-1) may underlie neurodegeneration in amyotrophic lateral sclerosis (ALS). However, the detailed role of GLT-1 in the pathogenies of ALS remains controversial. To assess this issue, here we elucidated structural alterations associated with dysregulation of glutamate homeostasis using SOD1(G93A) mice, a genetic model of familial ALS. We first examined the viability of α-motoneurons in the lumbar spinal cord of SOD1(G93A) mice. Measurement of the soma size and density indicated that α-motoneurons might be intact at 9weeks of age (presymptomatic stage), then soma shrinkage began at 15weeks of age (progressive stage), and finally neuronal density declined at 21weeks of age (end stage). Next, we carried out the line profile analysis, and found that the coverage of α-motoneurons by GLT-1-positive (GLT-1(+)) astrocytic processes was decreased only at 21weeks of age, while the reduction of coverage of α-motoneurons by synaptophysin-positive (SYP(+)) presynaptic terminals began at 15weeks of age. Interestingly, the coverage of α-motoneurons by VGluT2(+) presynaptic terminals was transiently increased at 9weeks of age, and then gradually decreased towards 21weeks of age. On the other hand, there were no time-dependent alterations in the coverage of α-motoneurons by GABAergic presynaptic terminals. These findings suggest that VGluT2 and GLT-1 may be differentially involved in the pathogenesis of ALS via abnormal glutamate homeostasis at the presymptomatic stage and end stage of disease, respectively.Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

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