Huntington's disease pattern of transcriptional dysregulation in the absence of mutant huntingtin is produced by knockout of neuronal GLT-1. (February 2019)

• Record Type: Journal Article
• Authors: Laprairie, Robert B.; Petr, Geraldine T.; Sun, Yan; Fischer, Kathryn D.; Denovan-Wright, Eileen M.; Rosenberg, Paul A.
• Is Part Of: Neurochemistry international. Volume 123(2019)
• Page Start: 85
• Page End: 94
• Publication Date: 2019-02
• Subjects: EAAT2 -- Dynamin -- Cannabinoid -- Dopamine receptor -- PDE10 -- Preproenkephalin; Cb cerebellum -- CB1 type 1 cannabinoid receptor -- CB2 type 2 cannbinoid receptor -- D2 type 2 dopamine receptor -- DARPP-32 dopamine and cAMP-regulated protein phosphatase 32 kDA -- Dnm1 dynamin-1 -- EAAT1 (GLAST) Excitatory amino acid tranporter 1 -- EAAT2 (GLT-1, slc1a2) Excitatory amino acid transporter 2 -- EAAT3 (EAAC1) Excitatory amino acid transporter 3 -- EAAT4 Excitatory amino acid transporter 4 -- EAAT5 Excitatory amino acid transporter 5 -- HD Huntington's disease -- MCtx motor cortex -- NAcc nucleus accumbens -- NGFIA nerve growth factor-induced clone A -- nGLT-1−/− (synGLT-1 KO) conditional neuronal GLT-1 knockout -- OD optical density -- PDE1B phosphodiesterase 1B -- PDE10A phosphodiesterase 10A -- PFc prefrontal cortex -- ppENK preproenkephalin -- RT reverse transcriptase -- SNr substantia nigra -- Str striatum -- Th thalmus -- VTA ventral tagmental area -- and WT wild-type; Neurochemistry -- Periodicals; Neurochemistry -- Periodicals; Neurochimie -- Périodiques; Neurochemistry; Periodicals; 612.804205
• DOI: 10.1016/j.neuint.2018.04.015
• Languages: English
• ISSNs: 0197-0186

Abstract

Abstract: GLT-1 is the major glutamate transporter in the brain, and is expressed in astrocytes and in axon terminals in the hippocampus, cortex, and striatum. Neuronal GLT-1 accounts for only 5–10% of total brain GLT-1 protein, and its function is uncertain. In HD, synaptic dysfunction of the corticostriate synapse is well-established. Transcriptional dysregulation is a key feature of HD. We hypothesized that deletion of neuronal GLT-1, because it is expressed in axon terminals in the striatum, might produce a synaptopathy similar to that present in HD. If true, then some of the gene expression changes observed in HD might also be observed in the neuronal GLT-1 knockout. In situ hybridization using 33 P labeled oligonucleotide probes was carried out to assess localization and expression of a panel of genes known to be altered in expression in HD. We found changes in the expression of cannabinoid receptors 1 and 2, preproenkaphalin, and PDE10A in the striatum of mice in which the GLT-1 gene was inactivated in neurons by expression of synapsin-Cre, compared to wild-type littermates. These changes in expression were observed at 12 weeks of age but not at 6 weeks of age. No changes in DARPP-32, PDE1B, NGFIA, or β-actin expression were observed. In addition, we found widespread alteration in expression of the dynamin 1 gene. The changes in expression in the neuronal GLT-1 knockout of genes thought to exemplify HD transcriptional dysregulation suggest an overlap in the synaptopathy caused by neuronal GLT-1 deletion and HD. These data further suggest that specific changes in expression of cannabinoid receptors, preproenkephalin, and PDE10A, considered to be the hallmark of HD transcriptional dysregulation, may be produced by an abnormality of glutamate homeostasis under the regulation of neuronal GLT-1, or a synaptic disturbance caused by that abnormality, independently of mutation in huntingtin . Highlights: Transcriptional dysregulation was assessed in a knockout of GLT-1 confined to neurons. A panel of genes was assayed known to be altered in Huntington's disease. Similar changes in certain genes were observed in the neuronal GLT-1 KO as in HD. Expression changes in HD may be due a synaptopathy caused by glutamate dyshomeostasis.