Huntington disease mice exhibit a TCF7L2-responsive suppression of both homeostatic and compensatory remyelination
Ontology highlight
ABSTRACT: PDGFRA-EGFP+ striaal cells were isolated for bulk RNA-sequencing from R6/2 (6wk and 12wk) and zQ175 (12wk and 1yr) HD mice and littermate controls.
Project description:Our working hypothesis is that two genetic factors A (compromized Rarβ expression in Rarβ+/- mice) and B (mutant form of huntingtin; R6/1 Tg/0) can synergise in generating physiopathology of Huntington disease. To address this point we performed comparative transcritomics in the nucleus accumbens (NAc) for 4 experimental groups : 1) R6/1 Tg/0 ; Rarβ+/-, (n=3); 2) R6/1 Tg/0 ; Rarβ+/+, (n=3); 3) R6/1 0/0 ; Rarβ+/-, (n=3); 4) R6/1 0/0 ; Rarβ+/+ (n=2).
Project description:Cyclic GMP–AMP synthase (cGAS) and its downstream effector, stimulator of interferon genes (STING), form a central cytosolic DNA–sensing pathway that drives innate immune activation and pro-inflammatory cytokine production. We previously reported that cGAS is upregulated in Huntington disease (HD) cellular models, where it modulates autophagy and inflammatory signaling. However, its in vivo contribution to HD pathogenesis has remained unresolved. Here, we genetically ablated cGAS in zQ175 knock-in HD mice, a model that closely recapitulates hallmark features of human HD, and conducted longitudinal behavioral analyses from 2 to 14 months of age. cGAS deletion significantly ameliorated HD-associated motor impairments, as evidenced by improved rotarod performance, enhanced coordination on beam walk, and better outcomes across a comprehensive behavioral battery. It also mitigated the progressive body-weight loss characteristic of zQ175 mice. Analysis of brain sections further revealed that cGAS deletion reduced the enlargement of lateral ventricles and attenuated both astrogliosis and microgliosis in the striatum. While cGAS loss produced minimal effects in wild-type littermates, transcriptomic profiling of HD brains showed downregulation of genes associated with development and cell–cell communication (Mid1-ps1, Slc45a3, Ilvbl, Col5a3) and upregulation of transcripts linked to ion transport and synaptic activity (Pgam2, Nos1, Cort, RasGef1a). Targeted lipidomics uncovered elevated levels of bioactive immunoregulatory lipids—particularly 12-HETE (ω-6) and 12-HEPE (ω-3)—in HD mice lacking cGAS. Finally, to assess therapeutic potential of cGAS-STING pathway, we pharmacologically inhibited STING using H-151 in zQ175 mice, which led to improved age-dependent motor performance. Collectively, these findings identify cGAS as a critical contributor to HD pathogenesis and support cGAS–STING pathway inhibition as a promising therapeutic avenue for Huntington disease.
Project description:Glial pathology is a significant contributor to disease pathogenesis in Huntington disease (HD), and neonatal glial replacement can delay disease progression and rescue aspects of behavior in mouse models of HD. Here we asked if the transplantation of normal human glial progenitor cells (hGPCs) into adult HD mice might similarly ameliorate phenotype. We found that the introduction of hGPCs into the striata of adult R6/2 HD mice significantly ameliorated their motor and cognitive phenotypes, extended their survival, and rescued aspects of medium spiny neuronal dendritic architecture. To establish the basis for this effect, we used retrograde labeling of striatal MSNs with glycoprotein-deleted rabies virus in hGPC-engrafted adult R6/2 mice to discover that the dendritic architecture of striatal MSNs was partially restored in adult-engrafted mice. These findings suggest that glial replacement may delay disease progression in HD, and that this is associated with the dynamic reorganization of medium spiny neuron dendritic architecture.
Project description:Previous studies have suggested a strong association between lower MSH3 expression, reduced somatic repeat expansion, and slower disease onset and progression. The effects of a homozygous knock-out in the Msh3 gene on transcriptome phenotypes in striatum in six-month-old WT and zQ175 mice were studied. Striatum was isolated from 6-month-old mice. Transcriptomic analysis (RNASeq) was performed on four genotypes with 8 replicates per genotype: WT (WT for Htt and Msh3), zQ175 (zQ175 for Htt, WT for Msh3), WT.Msh3.HOM (WT for Htt, Homozygous for Msh3 KO), and zQ175.Msh3.HOM (zQ175 for Htt, Homozygous for Msh3 KO).