Chronic optogenetic stimulation of Bergman glia leads to dysfunction of EAAT1 and Purkinje cell death, mimicking the events caused by expression of pathogenic ataxin-1

• Published in: Neurobiology of disease 2021-07, Vol.154, p.105340-105340, Article 105340
• Main Authors: Shuvaev, Anton N., Belozor, Olga S., Mozhei, Oleg, Yakovleva, Dariya A., Potapenko, Ilya V., Shuvaev, Andrey N., Smolnikova, Marina V., Salmin, Vladimir V., Salmina, Alla B., Hirai, Hirokazu, Teschemacher, Anja G., Kasparov, Sergey
• Format: Article
• Language: English
• Subjects: Animals; Ataxin-1 - biosynthesis; Ataxin-1 - genetics; Bergmann glia; Cell Death - physiology; Cerebellum; Excitatory Amino Acid Transporter 1 - antagonists & inhibitors; Excitatory Amino Acid Transporter 1 - biosynthesis; Excitatory Amino Acid Transporter 1 - genetics; Excitatory amino acid transporter type 1; Gene Expression; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neuroglia - metabolism; Neuroglia - pathology; Optogenetics - adverse effects; Photic Stimulation - adverse effects; Purkinje cell; Purkinje Cells - metabolism; Purkinje Cells - pathology; Spinocerebellar ataxia type 1
• ISSN: 0969-9961; 1095-953X
• DOI: 10.1016/j.nbd.2021.105340

Bergmann glia (BG) are highly specialized radial astrocytes of the cerebellar cortex, which play a key role in the uptake of synaptic glutamate via the excitatory amino acid transporter EAAT1. Multiple lines of evidence suggest that in cerebellar neurodegenerative diseases reactive BG has a negative impact on neuronal function and survival through compromised EAAT activity. A family of such diseases are those caused by expansion of CAG repeats in genes of the ataxin family, resulting in spinocerebellar ataxias (SCA). We investigated the contribution of BG to the pathogenesis of cerebellar neurodegeneration in a model of SCA1, which was induced by expression of a polyglutamine mutant of ataxin-1 (ATXN1[Q85]) in BG specifically. We compared the outcomes with a novel model where we triggered excitotoxicity by a chronic optogenetic activation of BG with channelrhodopsin-2 (ChR2). In both cases we detected evidence of reduced glutamate uptake manifested by prolongation of excitatory postsynaptic currents in Purkinje cells which is consistent with documented reduction of expression and/or function of EAAT1. In both models we detected astroglyosis and Purkinje cells atrophy. Finally, the same pattern was detected in a knock-in mouse which expresses a polyglutamine mutant ataxin-1 ATXN1[Q154] in a non-cell-selective manner. Our results suggest that ATXN1[Q85] and ChR2-induced insult targeted to BG closely mimics SCA1 pathology, where excessive glutamate signaling appears to be a common feature likely being an important contributor to cerebellar neurodegeneration. [Display omitted] •A novel model of reactive astroglyosis based on prolonged optogenetic activation of Bergman glia has been developed.•Lentiviral expression of a polyglutamine mutant of ataxin-1 (ATXN1[Q85]) in BG SCA1, resulted in neurodegeneration similar to that caused by optogenetic overstimulation.•Reactive BG contributes to neurodegeneration of cerebellum through impairment of EAAT1.•Excitotoxicity caused by excessive extracellular glutamate appears to be an important contributor to neurodegeneration in SCA-1 models.