Local and Global Abnormalities in Pre-symptomatic Huntington's Disease Revealed by 7T Resting-state Functional MRI

Paroxysmal Kinesigenic Dyskinesia: Genetics and Pathophysiological Mechanisms

Paroxysmal kinesigenic dyskinesia (PKD), the most common type of paroxysmal movement disorder, is characterized by sudden and brief attacks of choreoathetosis or dystonia triggered by sudden voluntary movements. PKD is mainly caused by mutations in the PRRT2 or TMEM151A gene. The exact pathophysiological mechanisms of PKD remain unclear, although the function of PRRT2 protein has been well characterized in the last decade. Based on abnormal ion channels and disturbed synaptic transmission in the absence of PRRT2, PKD may be channelopathy or synaptopathy, or both. In addition, the cerebellum is regarded as the key pathogenic area. Spreading depolarization in the cerebellum is tightly associated with dyskinetic episodes. Whereas, in PKD, other than the cerebellum, the role of the cerebrum including the cortex and thalamus needs to be further investigated.

HAP40 modulates mutant Huntingtin aggregation and toxicity in Huntington's disease mice

Huntington's disease (HD) is a monogenic neurodegenerative disease, caused by the CAG trinucleotide repeat expansion in exon 1 of the Huntingtin (HTT) gene. The HTT gene encodes a large protein known to interact with many proteins. Huntingtin-associated protein 40 (HAP40) is one that shows high binding affinity with HTT and functions to maintain HTT conformation in vitro. However, the potential role of HAP40 in HD pathogenesis remains unknown. In this study, we found that the expression level of HAP40 is in parallel with HTT but inversely correlates with mutant HTT aggregates in mouse brains. Depletion of endogenous HAP40 in the striatum of HD140Q knock-in (KI) mice leads to enhanced mutant HTT aggregation and neuronal loss. Consistently, overexpression of HAP40 in the striatum of HD140Q KI mice reduced mutant HTT aggregation and ameliorated the behavioral deficits. Mechanistically, HAP40 preferentially binds to mutant HTT and promotes Lysine 48-linked ubiquitination of mutant HTT. Our results revealed that HAP40 is an important regulator of HTT protein homeostasis in vivo and hinted at HAP40 as a therapeutic target in HD treatment.

Application Value of Serum Neurofilament Light Protein for Disease Staging in Huntington's Disease

BACKGROUND

Neurofilament light protein (NfL) has been proven to be a sensitive biomarker for Huntington's disease (HD). However, these studies did not include HD patients at advanced stages or with larger CAG repeats (>50), leading to a knowledge gap of the characteristics of NfL.

METHODS

Serum NfL (sNfL) levels were quantified using an ultrasensitive immunoassay. Participants were assessed by clinical scales and 7.0 T magnetic resonance imaging. Longitudinal samples and clinical data were obtained.

RESULTS

Baseline samples were available from 110 controls, 90 premanifest HD (pre-HD) and 137 HD individuals. We found levels of sNfL significantly increased in HD compared to pre-HD and controls (both P < 0.0001). The increase rates of sNfL were differed by CAG repeat lengths. However, there was no difference in sNfL levels in manifest HD from early to late stages. In addition, sNfL levels were associated with cognitive measures in pre-HD and manifest HD group, respectively. The increased levels of sNfL were also closely related to microstructural changes in white matter. In the longitudinal analysis, baseline sNfL did not correlate with subsequent clinical function decline. Random forest analysis revealed that sNfL had good power for predicting disease onset.

CONCLUSIONS

Although sNfL levels are independent of disease stages in manifest HD, it is still an optimal indicator for predicting disease onset and has potential use as a surrogate biomarker of treatment effect in clinical trials. © 2023 International Parkinson and Movement Disorder Society.

Cognition-oriented treatments and physical exercise on cognitive function in Huntington's disease: a systematic review

Cognitive impairment is prevalent in Huntington's disease (HD), with no treatments currently available. While cognition-oriented treatments and physical exercise have shown efficacy in improving cognition in other populations, they have not been systematically reviewed in HD. This systematic review aims to examine the effects of cognitive and exercise interventions on cognition in HD, along with effects on psychosocial function, functional independence, and neuroimaging outcomes. Seventeen studies (three cognitive, seven exercise, seven combining cognitive and physical exercise) were included. While there was generally low certainty of evidence, interventions that included cognitive training appeared to have larger effect sizes on cognition, while physical exercise (alone or combined with cognitive rehabilitation or stimulation) showed negligible effect sizes. On the other hand, combined interventions had larger effects on psychosocial function. Finally, effects on functional independence appeared negligible following exercise and combined interventions, and effects on neuroimaging outcomes were inconclusive. Larger studies should seek to confirm the benefits of cognitive and physical interventions, and further explore changes in functional independence and neural outcomes.

Aberrant resting-state brain activity in Huntington's disease: A voxel-based meta-analysis

Introduction

Functional neuroimaging could provide abundant information of underling pathophysiological mechanisms of the clinical triad including motor, cognitive and psychiatric impairment in Huntington's Disease (HD).

Methods

We performed a voxel-based meta-analysis using anisotropic effect size-signed differential mapping (AES-SDM) method.

Results

6 studies (78 symptomatic HD, 102 premanifest HD and 131 healthy controls) were included in total. Altered resting-state brain activity was primarily detected in the bilateral medial part of superior frontal gyrus, bilateral anterior cingulate/paracingulate gyrus, left insula, left striatum, right cortico-spinal projections area, right inferior temporal gyrus area, right thalamus, right cerebellum and right gyrus rectus area. Premanifest and symptomatic HD patients showed different alterative pattern in the subgroup analyses.

Discussion

The robust and consistent abnormalities in the specific brain regions identified in the current study could help to understand the pathophysiology of HD and explore reliable neuroimaging biomarkers for monitoring disease progression, or even predicting the onset of premanifest HD patients.