Huntingtin Research Articles

Inhibitor-based modulation of huntingtin aggregation mechanisms mitigates fibril-induced cellular stress

Huntington’s disease (HD) is a neurodegenerative disorder in which mutated fragments of the huntingtin protein (Htt) undergo misfolding and aggregation. Since aggregated proteins can cause cellular stress and cytotoxicity, there is an interest in the development of small molecule aggregation inhibitors as potential modulators of HD pathogenesis. Here, we study how a polyphenol modulates the aggregation mechanism of huntingtin exon 1 (HttEx1) even at sub-stoichiometric ratios. Sub-stoichiometric amounts of curcumin impacted the primary and/or secondary nucleation events, extending the pre-aggregation lag phase. Remarkably, the disrupted aggregation process changed both the aggregate structure and its cell metabolic properties. When administered to neuronal cells, the ‘break-through’ protein aggregates induced significantly reduced cellular stress compared to aggregates formed in absence of inhibitors. Structural analysis by electron microscopy, small angle X-ray scattering (SAXS), and solid-state NMR spectroscopy identified changes in the fibril structures, probing the flanking domains in the fuzzy coat and the fibril core. We propose that changes in the latter relate to the presence or absence of polyglutamine (polyQ) β-hairpin structures. Our findings highlight multifaceted consequences of small molecule inhibitors that modulate the protein misfolding landscape, with potential implications for treatment strategies in HD and other amyloid disorders.

Asymmetric brain atrophy in Huntington's disease: A postmortem MRI study.

BackgroundHuntington's disease is a progressive, autosomal dominant, neurodegenerative disease caused by a CAG repeat expansion in the HTT gene. Medium spiny neurons of the striatum are especially vulnerable to the disease, and atrophy of the caudate and putamen can be documented by neuroimaging years before the onset of symptoms.ObjectiveIn this study, we aimed to characterize region-specific gray and white matter differences between Huntington's disease patients and controls.MethodsWe conducted a postmortem MRI study of the brains of 15 adults diagnosed with symptomatic Huntington's disease and 26 control subjects, aiming to compare the differences in regional grey and white matter volumes between the two groups.ResultsThe study revealed decreased volumes in both grey and white matter in patients with Huntington's disease, with the largest effect sizes observed in caudate and putamen. Notably, the atrophy predominantly affected the left hemisphere, particularly impacting grey and white matter regions adjacent to the pars opercularis, precentral, supramarginal, and pars orbitalis gyri, and the lateral orbitofrontal cortex. In the control group, asymmetry stems from larger left hemisphere regions compared to right, whereas an opposite pattern is observed in the Huntington's disease group.ConclusionsThese results suggest progressive, diffuse, and asymmetric grey and white matter atrophy occurs in Huntington's disease. The reasons for this asymmetry remain unknown; however, our study provides a more detailed characterization of previously reported grey and white matter changes in Huntington's disease, as observed through postmortem histopathological and MRI studies.

Altered Huntingtin-Chromatin Interactions Predict Transcriptional and Epigenetic Changes in Huntington's Disease Mouse Models.

While progressive striatal gene expression changes and epigenetic alterations are a prominent feature of Huntington's disease (HD), the mechanistic basis remains poorly understood. Using chromatin immunoprecipitation and sequencing (ChIP-seq), we show that the huntingtin protein (HTT) reproducibly occupies specific locations in the mouse genome. Striatal HTT ChIP-seq peaks were enriched in coding regions of spiny projection neuron identity genes, which are found to have reduced expression in HD patients and mouse models, and had reduced occupancy in expanded polyglutamine HTT knock-in mice (HttQ111/Q111). Conversely, HTT occupancy was depleted near genes that are up-regulated in HD. ChIP-seq of striatal histone modifications revealed genotype-specific colocalization of HTT with active chromatin marks and enhancer of zeste homolog 2 (EZH2), a key enzymatic component of the PRC2 complex. Near genes that are differentially regulated in HD, greater HTT occupancy in HttQ111/Q111 vs. wildtype mice was associated with increased EZH2 binding, increased H3K4me3, and decreased H3K27me3. Our study suggests that huntingtin-chromatin interactions may play a role in organizing chromatin and promoting cell type-specific gene expression, with HTT occupancy predicting transcriptional dysregulation in HD.

Examination of Anti-Inflammatory Effects After Propionate Supplementation in the R6/2 Mouse Model of Huntington's Disease.

Huntington's disease is a progressive, untreatable neurodegenerative disorder caused by a mutation in the Huntingtin gene. Next to neurodegeneration, altered immune activation is involved in disease progression. Since central nervous system inflammation and dysfunction of immune cells are recognized as driving characteristics, immunomodulation might represent an additional therapeutic strategy. Short-chain fatty acids were known to have immunomodulatory effects in neuroinflammatory diseases, such as multiple sclerosis. In this study, R6/2 mice were treated daily with 150 mM propionate. Survival range, body weight, and motor abilities were monitored. In striatal and cortical samples, neuronal survival was analyzed by immunofluorescence staining of NeuN-positive cells and expression levels of BDNF mRNA by real-time polymerase chain reaction. As inflammatory marker TNFα mRNA and IL-6 mRNA were quantified by rtPCR, iNOS-expressing cells were counted in immunologically stained brain slides. Microglial activation was evaluated by immunofluorescent staining of IBA1-positive cells and total IBA1 protein by Western Blot, in addition, SPI1 mRNA expression was quantified by rtPCR. Except for clasping behavior, propionate treatment did neither improve the clinical course nor mediated neuronal protection in R6/2 mice. Yet there was a mild anti-inflammatory effect in the CNS, with (i) reduction in SPI1-mRNA levels, (ii) reduced iNOS positive cells in the motor cortex, and (iii) normalized TNFα-mRNA in the motor cortex of propionate-treated R6/2 mice. Thus, Short-chain fatty acids, as an environmental factor in the diet, may slightly alleviate symptoms by down-regulating inflammatory factors in the central nervous system. However, they cannot prevent clinical disease progression or neuronal loss.

Exploring Cordycepin as a Neuroprotective Agent in Huntington's Disease: InVitro and InVivo Insights.

Huntington's disease (HD) is a challenging neurodegenerative disorder linked to Huntingtin (HTT) gene mutation, lacking an effective cure despite numerous therapeutic attempts. Cordyceps sinensis, recognized for its health benefits, particularly its constituent cordycepin, exhibits neuroprotective effects in various neurodegenerative diseases. However, the neuroprotective potential of cordycepin in HD remains insufficiently explored. In this study, invitro experiments using HD cell models demonstrate that cordycepin treatment enhances cell survival, slightly diminishes mutant HTT aggregates, and improves neuronal formation. Invivo investigations on R6/2 HD transgenic mice reveal a modest increase in body weight and a slight amelioration in pathological aggregates following cordycepin administration, although behavioral changes are not significant. While the underlying mechanisms remain unexplored, the findings suggest cordycepin's promise as a supplementary therapeutic for HD, providing neuroprotective effects and reducing mutant protein aggregates.

Multi-epitope immunocapture of huntingtin reveals striatum-selective molecular signatures.

Huntington's disease (HD) is a debilitating neurodegenerative disorder affecting an individual's cognitive and motor abilities. HD is caused by a mutation in the huntingtin gene producing a toxic polyglutamine-expanded protein (mHTT) and leading to degeneration in the striatum and cortex. Yet, the molecular signatures that underlie tissue-specific vulnerabilities remain unclear. Here, we investigate this aspect by leveraging multi-epitope protein interaction assays, subcellular fractionation, thermal proteome profiling, and genetic modifier assays. The use of human cell, mouse, and fly models afforded capture of distinct subcellular pools of epitope-enriched and tissue-dependent interactions linked to dysregulated cellular pathways and disease relevance. We established an HTT association with nearly all subunits of the transcriptional regulatory Mediator complex (20/26), with preferential enrichment of MED15 in the tail domain. Using HD and KO models, we find HTT modulates the subcellular localization and assembly of the Mediator. We demonstrated striatal enriched and functional interactions with regulators of calcium homeostasis and chromatin remodeling, whose disease relevance was supported by HD fly genetic modifiers assays. Altogether, we offer insights into tissue- and localization-dependent (m)HTT functions and pathobiology.

Molecular mechanisms and biomarkers in neurodegenerative disorders: a comprehensive review.

Neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), Amyotrophic Lateral Sclerosis (ALS), and Huntington's disease (HD), are significant global health challenges, owing to their profound impact on cognitive, motor, and behavioral functions. The etiology and progression of these disorders are influenced by a complex interplay of environmental factors and genetic predispositions with specific genetic markers, such as mutations in the APOE and HTT genes, which play pivotal roles. Current therapeutic interventions predominantly focus on symptom management; however, emerging strategies, including gene therapies, anti-amyloid agents, and neuroprotective approaches, are designed to directly target the underlying disease mechanisms. Advances in biomarker discovery and imaging methodologies have emerged as essential tools for early diagnosis and monitoring of therapeutic efficacy in these disorders. In the context of AD, cerebrospinal fluid (CSF) amyloid-beta (Aβ) and tau levels, along with positron emission tomography (PET) imaging, are well-established biomarkers. Similarly, CSF alpha-synuclein and dopamine transporter (DAT) imaging have been employed as diagnostic tools for PD. Moreover, emerging biomarkers, such as blood-based tau and the Aβ42/40 ratio for AD, as well as the neurofilament light chain (NfL) for ALS and PD, hold promise for enhancing early diagnostic accuracy and facilitating the longitudinal assessment of disease progression. This study comprehensively examined the molecular mechanisms underlying these neurodegenerative disorders, focusing on amyloid-beta plaque deposition and tau protein aggregation in AD, alpha-synuclein misfolding in PD, and aberrant protein aggregation in ALS and HD, thereby contributing to a deeper understanding of the pathophysiological basis of these disorders.

Progressively reduced cerebral oxygen metabolism and elevated plasma NfL levels in the zQ175DN mouse model of Huntington's disease.

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by a CAG-repeat expansion in exon-1 of the huntingtin gene. Currently, no disease-modifying therapies are available, with a significant challenge in evaluating therapeutic efficacy before clinical symptoms emerge. This highlights the need for early biomarkers and intervention strategies. Therefore, it is essential to develop and characterize accurate mouse models and identify early biomarkers for preclinical therapeutic development. In this study, we characterized the pathological progression of the heterozygous zQ175 neo-deleted knock in (zQ175DN) mouse model across four age groups: 3, 6, 10, and 16 months to identify human translatable outcome measures. T2-relaxation-under-spin-tagging (TRUST) MRI was used to assess global CMRO 2 , while T2-weighted MRI was used to analyze brain volumes. Significant brain volume loss was detected as early as 6 months of age, worsening progressively with age in the zQ175 DN mice, resembling HD brain volumetric changes. A decline in CMRO 2 was observed in 6-month-old zQ175 DN mice, with significant and progressive reductions in 10- and 16-months old HD mice. Additionally, PHP1-positive mutant huntingtin (mHTT) aggregates were present in the striatum of zQ175 DN mice at all four age groups, with intranuclear localization prior to 6 months, transitioning to both intranuclear and neuropil aggregates in older zQ175 DN mice, suggesting that the localization of mHTT aggregates may reflect the severity of HD pathogenesis. Interestingly, plasma neurofilament light chain (NfL) protein concentrations were significantly elevated at 6 months of age and older zQ175DN mice. These findings provide valuable insights for selecting outcome measures in preclinical evaluations of HD therapies using the zQ175 DN mouse model.

Transcriptomic analysis of intracellular RNA granules and small extracellular vesicles: Unmasking their overlap in a cell model of Huntington's disease.

Transcriptomic analysis of intracellular RNA granules and small extracellular vesicles: Unmasking their overlap in a cell model of Huntington's disease.

Post-translational modifications orchestrate the intrinsic signaling bias of GPR52.

Despite recent advances in G-protein-coupled receptor (GPCR) biology, the regulation of GPCR activation, signaling and function by post-translational modifications (PTMs) remains largely unexplored. In this study of GPR52, an orphan GPCR with exceedingly high constitutive G-protein activity that is emerging as a neurotherapeutic target, we discovered its disproportionately low arrestin recruitment activity. After profiling the N-glycosylation and phosphorylation patterns, we found that these two types of PTMs differentially shape the intrinsic signaling bias of GPR52. While N-terminal N-glycosylation promotes constitutive Gs signaling possibly through favoring the self-activating conformation, phosphorylation in helix 8, to our great surprise, suppresses arrestin recruitment and attenuates receptor internalization. In addition, we uncovered the counteracting roles of N-glycosylation and phosphorylation in modulating GPR52-dependent accumulation of the huntingtin protein in brain striatal cells. Our study provides new insights into the regulation of intrinsic signaling bias and cellular function of an orphan GPCR through distinct PTMs in different motifs.

Downregulation of Pten Improves Huntington's Disease Phenotype by Reducing Htt Aggregates and Cell Death.

Huntington's disease (HD) is a dominantly inherited neurodegenerative disorder that stems from the expansion of CAG repeats within the coding region of Huntingtin (HTT) gene. Currently, there exists no effective therapeutic intervention that can prevent the progression of the disease. Our study aims to identify a novel genetic modifier with therapeutic potential. We employ transgenic flies containing HTT.ex1.Q93 and mRFP-HTT.588.Q138 constructs, which encode mutant pathogenic Huntingtin (Htt) proteins featuring 93 and 138 polyglutamine (Q) repeats respectively. The resultant mutant proteins cause the loss of photoreceptor neurons in the eye and a progressive loss of neuronal tissues in the brain and motor neurons in Drosophila. Several findings have demonstrated the association of HD with growth factor signaling defects. Phosphatase and tensin homolog (Pten) have been implicated in the negative regulation of the Insulin signaling/receptor tyrosine signaling pathway which regulates the growth and survival of cells. In the present study, we downregulated Pten and found a significant improvement in morphological phenotypes in the eye, brain, and motor neurons. These findings were further correlated with the enhancement of the functional vision and climbing ability of the flies. We also found the reduction in both Htt aggregate and caspase levels which are involved in the apoptotic pathway. In alignment with the genetic modulation of Pten, we elucidated the protective role of Pten inhibition through the utilization of VO-OHpic. VO-OHpic improved the climbing ability of flies and reduced the poly(Q) aggregates and apoptosis levels. A similar reduction in Htt aggregates was observed in the mouse neuronal inducible HD cell line model. Our study illustrates that Pten inhibition is a potential therapeutic approach for HD.

Structural-functional analyses of the huntingtin/HAP40 complex in Drosophila and humans

Huntington’s disease (HD) is a neurodegenerative disorder caused by an abnormal CAG expansion in the Huntingtin (HTT) gene. Given its simple genetic cause but complex pathogenic mechanisms, interest in targeting HTT for HD treatment is growing, necessitating a clear understanding of HTT regulation. HTT protein primarily exists in a core complex with HAP40, forming a highly ordered structure with two large globular domains connected by a bridge. We previously demonstrated that HAP40 is conserved in Drosophila, controls HTT’s function, protein stability, and levels, and is a potential modifier of HD pathogenesis, supporting its central role in HTT regulation. Here, we showed that HTT synergizes with HAP40 to induce novel gain-of-function effects in Drosophila when overexpressed. Protein modeling revealed that despite their prominent evolutionary and sequence divergence, the fly and human HTT-HAP40 complexes share a high degree of structural similarity. Protein-contact maps and molecular simulations showed that HAP40 preferentially binds to HTT’s C-terminal domain in both complexes. By examining the interfacial contacts between HTT and HAP40 in fly and human complexes, we identified ten conserved bonds that are important for HAP40’s affinity for HTT. Finally, we showed that the conserved N-terminal BΦ motif in HAP40 is not essential for HTT binding but important for HAP40’s functions. Through the structural-functional analyses of the fly and human HTT-HAP40 complexes, our results support that the structural similarity underlies the functional conservation of the two complexes from these evolutionarily distant species and further uncover novel insight into HAP40 regulation and its interaction with HTT.

Huntingtin plays an essential role in the adult hippocampus.

The consequences of non-pathogenic huntingtin (HTT) reduction in the mature brain are of substantial importance as clinical trials for numerous HTT-lowering therapies are underway; many of which are non-selective in that they reduce both mutant and wild type protein variants. In this study, we injected CaMKII-promoted AAV-Cre directly into the hippocampus of adult HTT floxed mice to explore the role of wild-type huntingtin (wtHTT) in adult hippocampal pyramidal neurons and the broader implications of its loss. Our findings reveal that wtHTT depletion results in profound macroscopic morphological abnormalities in hippocampal structure, accompanied by significant reactive gliosis. At the synaptic level, we identified a marked reduction in presynaptic terminals 1-2months following wtHTT loss; this was contrasted by an increased density of postsynaptic mushroom spines and larger amplitudes of spontaneous excitatory postsynaptic currents, indicative of disrupted synaptic homeostasis. Furthermore, intrinsic neuronal excitability was significantly diminished in CA1 pyramidal neurons lacking wtHTT, and we observed a complete loss of NMDA receptor-dependent long-term potentiation. Unexpectedly, synapse density returned to control levels 6-8months following wtHTT loss, despite the ongoing presence of macroscopic morphological abnormalities, altered anxiety-related behaviors and clear impairments in spatial learning and memory. Overall, these findings uncover a previously unrecognized role of wtHTT as a critical regulator of hippocampal function in the mature brain, and highlight the hippocampus as a potentially vulnerable region to the adverse effects of non-selective HTT reduction.

Glutamine missense suppressor transfer RNAs inhibit polyglutamine aggregation.

Glutamine missense suppressor transfer RNAs inhibit polyglutamine aggregation.

Peripheral and central elevation of IL-8 in patients with Huntington's disease.

Huntington's Disease (HD) is a debilitating neurodegenerative condition characterized by motor, cognitive and psychiatric abnormalities. Immune hyperactivity and dysregulation are common in HD. In addition to the central nervous system, HD patients exhibit systemic innate immune activation and inflammation, which has been shown to contribute to the pathogenic effects of the Huntingtin gene mutation. Upregulation of inflammatory mediators including interferon gamma (IFN-γ) and interleukin (IL)-8 has been observed in animal Huntington's disease models. However, studies on HD patients remain limited. In this study, serum samples from 58 HD patients and 59 age- and gender-matched healthy control individuals were analysed using a bead-based assay, that enabled simultaneous measurement of 13 cytokines and chemokines. Additionally, publicly available transcriptomic data from brain tissues of HD patients and controls were examined. Our results confirm that IL-8 protein levels are significantly higher in HD patients compared to non-HD controls, with the highest levels observed in the moderate HD group. In the control group, we found significant positive correlations between IL-8 levels and both IL-17A and IL-10. However, these correlations were not observed in HD patients, where IL-8 levels were notably positively correlated with pro-inflammatory markers including IFNγ and IL-23. Interestingly, IL-17A levels demonstrated a negative correlation with disease parameters, including CAG trinucleotide repeat expansion and disease burden score. Furthermore, cytokines and chemokines such as IFNγ and monocyte chemoattractant protein 1 (MCP-1; CCL2) demonstrated positive correlations with the same disease parameters. In-depth analysis of publicly available bulk RNAseq, and single-nucleus RNA-sequencing (snRNAseq) data from two key HD-affected brain regions- the prefrontal cortex and striatum revealed that IL-8 expression is significantly increased in cortex samples from individuals with HD compared to non-HD controls. Moreover, snRNAseq data in the striatum showed higher IL-8 expression in HD patients than in non-HD controls, with a predominant expression in microglia. Overall, our findings support an upregulation of IL-8 in patients with HD, evident in both central degenerating brain regions, and peripheral blood samples. We identified unique immunological signatures associated with the severity of HD and provide potential biomarkers that may reflect immune-pathological mechanisms in HD patients.

Multiple Copper Ions Bind to and Promote the Oligomerization of Huntingtin Protein with Nonpathological Repeat Expansions.

Huntington's disease (HD) is a fatal neurodegenerative disease characterized by the expression of huntingtin protein (htt) that has a polyglutamine (CAG; polyQ) repeat domain consisting of 36 or more glutamines (mhtt). Historically, mhtt is more broadly associated with HD severity, as are elevated metal levels observed in HD patients. The depletion of wild-type (WT) htt (fewer than 36Qs) is also recognized as a contributing factor to HD progression; however, many questions remain about the interactions of biorelevant metals with WT htt and the impact of the interactions on protein aggregation. In the present work, we utilize a combination of biochemical assays and spectroscopic techniques to provide insights into the interaction of copper with an in vitro htt model (N171-17Q). Herein, we use sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and dynamic light scattering to show that the addition of equimolar or higher concentrations of Cu(II) to htt induces time- and temperature-dependent protein oligomerization/aggregation. Additionally, chelation assays, trapped ion mobility spectrometry, and mass spectrometry confirm the (i) rapid reduction of Cu(II) in the presence of N171-17Q htt, (ii) direct binding of multiple copper ions per protein, and (iii) complex Cu:htt speciation profile with a preference for three distinct Cu:htt states. These findings contribute to our molecular level understanding of copper's role in the depletion and oligomerization/aggregation of WT htt while underscoring the physiological significance of our work, its potential relevance to metal binding in mhtt, and its significance for identifying new avenues for biomarker exploration and therapeutic design strategies.

Neuroimaging Techniques in Huntington's Disease: A Critical Review.

Huntington's disease (HD) is a hereditary neurodegenerative disorder characterized by cognitive, neuropsychiatric and motor symptoms caused by a CAG trinucleotide repeat expansion in the huntingtin gene. Imaging techniques are crucial for understanding HD pathophysiology and monitoring disease progression. This review is targeted at general neurologists and movement disorders specialists with an interest in HD and aims to bring complex imaging, including new experimental techniques, closer to the practicing clinician. We provide a summary of findings from conventional structural, diffusion and functional imaging in HD studies, together with an update on emerging novel techniques, including multiparametric mapping, multi-shell diffusion techniques, ultra-high field 7-Tesla MRI, positron emission tomography and magnetoencephalography. Conventional imaging techniques have deepened our understanding of neuropathological progression in HD, from striatal atrophy to widespread cortical and white matter changes. The integration of novel imaging techniques reviewed has further improved our ability to interrogate, quantify and visualize disease-specific alterations with high precision. Novel imaging techniques have promising roles to further our understanding of HD pathology and as imaging markers for clinical trials, disease staging and therapeutic monitoring. Additionally, the synergistic potential of combining imaging modalities with molecular and genetic data, along with wet biomarkers and clinical data, will help provide a complete and comprehensive view of HD pathology and progression.

Antisense oligonucleotide-mediated MSH3 suppression reduces somatic CAG repeat expansion in Huntington's disease iPSC-derived striatal neurons.

Expanded CAG alleles in the huntingtin (HTT) gene that cause the neurodegenerative disorder Huntington's disease (HD) are genetically unstable and continue to expand somatically throughout life, driving HD onset and progression. MSH3, a DNA mismatch repair protein, modifies HD onset and progression by driving this somatic CAG repeat expansion process. MSH3 is relatively tolerant of loss-of-function variation in humans, making it a potential therapeutic target. Here, we show that an MSH3-targeting antisense oligonucleotide (ASO) effectively engaged with its RNA target in induced pluripotent stem cell (iPSC)-derived striatal neurons obtained from a patient with HD carrying 125 HTT CAG repeats (the 125 CAG iPSC line). ASO treatment led to a dose-dependent reduction of MSH3 and subsequent stalling of CAG repeat expansion in these striatal neurons. Bulk RNA sequencing revealed a safe profile for MSH3 reduction, even when reduced by >95%. Maximal knockdown of MSH3 also effectively slowed CAG repeat expansion in striatal neurons with an otherwise accelerated expansion rate, derived from the 125 CAG iPSC line where FAN1 was knocked out by CRISPR-Cas9 editing. Last, we created a knock-in mouse model expressing the human MSH3 gene and demonstrated effective in vivo reduction in human MSH3 after ASO treatment. Our study shows that ASO-mediated MSH3 reduction can prevent HTT CAG repeat expansion in HD 125 CAG iPSC-derived striatal neurons, highlighting the therapeutic potential of this approach.

Customizable virus-like particles deliver CRISPR-Cas9 ribonucleoprotein for effective ocular neovascular and Huntington's disease gene therapy.

In vivo CRISPR gene editing holds enormous potential for various diseases. Ideally, CRISPR delivery should be cell type-specific and time-restricted for optimal efficacy and safety, but customizable methods are lacking. Here we develop a cell-tropism programmable CRISPR-Cas9 ribonucleoprotein delivery system (RIDE) based on virus-like particles. The efficiency of RIDE was comparable to that of adeno-associated virus and lentiviral vectors and higher than lipid nanoparticles. RIDE could be readily reprogrammed to target dendritic cells, T cells and neurons, and significantly ameliorated the disease symptoms in both ocular neovascular and Huntington's disease models via cell-specific gene editing. In addition, RIDE could efficiently edit the huntingtin gene in patients' induced pluripotent stem cell-derived neurons and was tolerated in non-human primates. This study is expected to facilitate the development of in vivo CRISPR therapeutics.

Endothelial Dysfunction in Huntington's Disease: Pathophysiology and Therapeutic Implications.

Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms. While traditionally viewed through the lens of neuronal dysfunction, emerging evidence highlights the critical role of endothelial dysfunction in HD pathogenesis. This review provides a comprehensive overview of endothelial dysfunction in HD, drawing on findings from both animal models and human studies. Key features of endothelial dysfunction in HD include impaired angiogenesis, altered cerebral blood flow, compromised neurovascular coupling and cerebrovascular reactivity, and increased blood-brain barrier permeability. Genetic factors such as the mutant huntingtin protein, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), Brain-derived neurotrophic factor (BDNF), and the adenosine A2A receptor (ADORA2A) interact to influence endothelial function in complex ways. Various therapeutic approaches targeting endothelial dysfunction, including antioxidants, nitric oxide enhancers, calcium channel blockers, statins, and metformin, have shown promise in preclinical HD models but face translational challenges, particularly regarding optimal timing of intervention and patient stratification. The implications of these findings suggest that reconceptualizing HD as a neurovascular disorder, rather than purely neuronal, could lead to more effective treatment strategies. Future research priorities should include: (1) developing validated vascular biomarkers for disease progression, (2) advancing neuroimaging techniques to monitor endothelial dysfunction in real-time. These directions will be crucial for bridging the current gap between preclinical promise and clinical success in vascular-targeted HD therapeutics.