Chloride Dysregulation and Impaired Gamma-Amino Butyric Acid Signaling in the Basal Ganglia in Huntington's Disease
Bibliographic record
Abstract
Huntington’s disease (HD) is an inherited neurodegenerative disorder caused by a cytosine-adenine-guanine (CAG) trinucleotide repeat expansion in Huntingtin (HTT) gene. The primary sites of degeneration are a group of nuclei called the basal ganglia which are essential for motor planning and voluntary movement. The basal ganglia contains two major pathways: the direct and indirect, which promote movement and inhibit unwanted movement, respectively. Neurons that form the beginnings of the indirect pathway are known to degenerate earlier in HD, though the cause of this enhanced susceptibility remains unclear. Accumulating evidence suggests that impaired synaptic inhibition within the basal ganglia circuitry may underlie this specific pattern of degeneration. Synaptic inhibition in the mature brain is largely mediated through gamma-amino butyric acid (GABA), which exerts fast hyperpolarizing inhibition by binding to chloride (Cl-)-permeable GABAA receptors (GABAARs). GABAergic inhibition requires low intracellular Cl- concentration ([Cl-]i), which is maintained by the antagonistic actions of Cl--exporting potassium (K+)- Cl- cotransporter 2 (KCC2) and Cl- -importing sodium (Na+)- K+ - Cl- cotransport 1 (NKCC1). However, when KCC2 function is reduced and/or NKCC1activity increases, [Cl-]i increases, consequently weakening synaptic inhibition. In my PhD thesis, I present three novel pieces of evidence that collectively demonstrate that Cl- dysregulation and altered GABAergic inhibition are key contributing factors to the development of motor deficits in two mouse models of HD. First, NKCC1 expression is increased and KCC2 function is reduced in the striatum, the major input structure of the basal ganglia. Second, KCC2 function is differentially altered in the direct and indirect pathways and GABAergic inhibition is switched to GABA-mediated excitation in the output structure of the indirect pathway. Finally, pharmacologically reducing pathological increases [Cl-]i delays motor behavioral deficits of R6/2 mice. Taken together, my PhD work not only significantly increases our understanding of the increased susceptibility of the indirect pathway but opens new possibilities where Cl- cotransporters may serve as therapeutic targets in the treatment of HD.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".