Deletion of the Sodium-Dependent Glutamate Transporter GLT-1 in Maturing Oligodendrocytes Attenuates Myelination of Callosal Axons During a Postnatal Phase of Central Nervous System Development

Abstract

The sodium-dependent glutamate transporter GLT-1 (EAAT2, SLC1A2) has been well-described as an important regulator of extracellular glutamate homeostasis in the central nervous system (CNS), a function that is performed mainly through its presence on astrocytes. There is, however, increasing evidence for the expression of GLT-1 in CNS cells other than astrocytes and in functional roles that are mediated by mechanisms downstream of glutamate uptake. In this context, GLT-1 expression has been reported for both neurons and oligodendrocytes (OLGs), and neuronal presynaptic presence of GLT-1 has been implicated in the regulation of glutamate uptake, gene expression, and mitochondrial function. Much less is currently known about the functional roles of GLT-1 expressed by OLGs. The data presented here provide first evidence that GLT-1 expressed by maturing OLGs contributes to the modulation of developmental myelination in the CNS. More specifically, using inducible and conditional knockout mice in which GLT-1 was deleted in maturing OLGs during a peak period of myelination (between 2 and 4 weeks of age) revealed hypomyelinated characteristics in the corpus callosum of preferentially male mice. These characteristics included reduced percentages of smaller diameter myelinated axons and reduced myelin thickness. Interestingly, this myelination phenotype was not found to be associated with major changes in myelin gene expression. Taken together, the data presented here demonstrate that GLT-1 expressed by maturing OLGs is involved in the modulation of the morphological aspects associated with CNS myelination in at least the corpus callosum and during a developmental window that appears of particular vulnerability in males compared to females.

Adult‐onset depletion of sulfatide leads to axonal degeneration with relative myelin sparing

“…Previous studies have reported that myelin and axon defects are more prone to axons of specific caliber (Thomason et al, 2022). Therefore, we used a similar binning approach (increments of 0.1 μm) to assess axonal caliber‐specific pathologies; however, no difference in axon caliber, or myelin thickness was detected (data not shown).…”

“…To specifically target ablation of the Cst gene in oligodendrocytes in the CNS, we purchased Plp CreERT mice (Jax Labs; stock # 005975) to induce recombination and mated them to the homozygous Cst floxed (Cst fl/fl ) line. The PLP CreERT line was chosen as the Cre driver line since this line has been routinely used to efficiently induce adult-onset gene ablation in the CNS in chronic studies (Pillai et al, 2009;Mei et al, 2013;Jablonska et al, 2016;de Logu et al, 2017de Logu et al, , 2020Thomason et al, 2022;Borges et al, 2023). In the original report of the generation of these mice, Doerflinger et al, (2003) showed that in the absence of tamoxifen, Cre remained cytoplasmic and there was no evidence of recombination.…”

Lysophosphatidic acid signaling via LPA6: A negative modulator of developmental oligodendrocyte maturation

“…GraphPad Prism (GraphPad Software Inc.; ) was used for all statistical analyses. Prior sample calculations were not performed: sample size was estimated based on previous studies of a similar nature (Dennis et al, 2008; Lafrenaye & Fuss, 2011; Martinez‐Lozada et al, 2014; Thomason et al, 2022; Waggener et al, 2013; Wheeler et al, 2015). Data were assessed for normality using the Shapiro–Wilk normality test prior to analysis.…”