Gene targeting techniques for Huntington's disease

Targeted protein degradation: expanding the technology to facilitate the clearance of neurotoxic proteins in neurodegenerative diseases

In neurodegenerative diseases (NDDs), disruptions in protein homeostasis hinder the clearance of misfolded proteins, causing the formation of misfolded protein oligomers and multimers. The accumulation of these abnormal proteins results in the onset and progression of NDDs. Removal of non-native protein is essential for cell to maintain proteostasis. In recent years, targeted protein degradation (TPD) technologies have become a novel means of treating NDDs by removing misfolded proteins through the intracellular protein quality control system. The TPD strategy includes the participation of two primary pathways, namely the ubiquitin-proteasome pathway (for instance, PROTAC, molecular glue and hydrophobic tag), and the autophagy-lysosome pathway (such as LYTAC, AUTAC and ATTEC). In this review, we systematically present the mechanisms of various TPD strategies employed for neurotoxic protein degradation in NDDs. The article provides an overview of the design, in vitro and in vivo anti-NDD activities and pharmacokinetic properties of these small-molecular degraders. Finally, the advantages, challenges and perspectives of these TPD technologies in NDDs therapy are discussed, providing ideas for further development of small molecule degraders in the realm of NDDs.

The role of SGK1 in neurologic diseases: A friend or foe?

Serum and glucocorticoid-regulated kinase 1 (SGK1), a member of the AGC family of serine/threonine protein kinases, is one of the most conserved protein kinases in eukaryotic evolution. SGK1 is expressed to varying degrees in various types of cells throughout the body, and plays an important role in hypertension, ion channels, oxidative stress, neurological disorders, and cardiovascular regulation. In recent years, a number of scholars have devoted themselves to the study of the role and function of SGK1 in neurological diseases. Therefore, this article reviews the role of SGK1 in Alzheimer's disease, Parkinson's disease, epilepsy, stroke and other neurological diseases in recent years, and puts forward some insights on the role of SGK1 in neurological diseases and its relationship with disease activities.

Mitochondrial dysfunction as a therapeutic strategy for neurodegenerative diseases: Current insights and future directions

Neurodegenerative diseases, as common diseases in the elderly, tend to become younger due to environmental changes, social development and other factors. They are mainly characterized by progressive loss or dysfunction of neurons in the central or peripheral nervous system, and common diseases include Parkinson's disease, Alzheimer's disease, Huntington's disease and so on. Mitochondria are important organelles for adenosine triphosphate (ATP) production in the brain. In recent years, a large amount of evidence has shown that mitochondrial dysfunction plays a direct role in neurodegenerative diseases, which is expected to provide new ideas for the treatment of related diseases. This review will summarize the main mechanisms of mitochondrial dysfunction in neurodegenerative diseases, as well as collating recent advances in the study of mitochondrial disorders and new therapies.

Decoding Neurodegeneration: A Review of Molecular Mechanisms and Therapeutic Advances in Alzheimer's, Parkinson's, and ALS

Neurodegenerative diseases, such as Alzheimer's, Parkinson's, ALS, and Huntington's, remain formidable challenges in medicine, with their relentless progression and limited therapeutic options. These diseases arise from a web of molecular disturbances-misfolded proteins, chronic neuroinflammation, mitochondrial dysfunction, and genetic mutations-that slowly dismantle neuronal integrity. Yet, recent scientific breakthroughs are opening new paths to intervene in these once-intractable conditions. This review synthesizes the latest insights into the underlying molecular dynamics of neurodegeneration, revealing how intertwined pathways drive the course of these diseases. With an eye on the most promising advances, we explore innovative therapies emerging from cutting-edge research: nanotechnology-based drug delivery systems capable of navigating the blood-brain barrier, gene-editing tools like CRISPR designed to correct harmful genetic variants, and stem cell strategies that not only replace lost neurons but foster neuroprotective environments. Pharmacogenomics is reshaping treatment personalization, enabling tailored therapies that align with individual genetic profiles, while molecular diagnostics and biomarkers are ushering in an era of early, precise disease detection. Furthermore, novel perspectives on the gut-brain axis are sparking interest as mounting evidence suggests that microbiome modulation may play a role in reducing neuroinflammatory responses linked to neurodegenerative progression. Taken together, these advances signal a shift toward a comprehensive, personalized approach that could transform neurodegenerative care. By integrating molecular insights and innovative therapeutic techniques, this review offers a forward-looking perspective on a future where treatments aim not just to manage symptoms but to fundamentally alter disease progression, presenting renewed hope for improved patient outcomes.

Prime editing: A gene precision editing tool from inception to present

Genetic mutations significantly contribute to the onset of diseases, with over half of the cases caused by single-nucleotide mutations. Advances in gene editing technologies have enabled precise editing and correction of mutated genes, offering effective treatment methods for genetic disorders. CRISPR/Cas9, despite its power, poses risks of inducing gene mutations due to DNA double-strand breaks (DSB). The advent of base editing (BE) and prime editing (PE) has mitigated these risks by eliminating the hazards associated with DNA DSBs, allowing for more precise gene editing. This breakthrough lays a solid foundation for the clinical application of gene editing technologies. This review discusses the principles, development, and applications of PE gene editing technology in various genetic mutation-induced diseases.

An insight into allele-selective approaches to lowering mutant huntingtin protein for Huntington's disease treatment

Huntington's disease (HD), a monogenic neurodegenerative disorder, stems from a CAG repeat expansion within the mutant huntingtin gene (HTT). This leads to a detrimental gain-of-function of the mutated huntingtin protein (mHTT). As of now, there exist no efficacious therapies to alter the disease progression. In view of the monogenetic mutation nature and an indispensable role of wild-type HTT in healthy neurodevelopment and cellular functions, the developing strategy of allele-selectively deleting/silencing mutant HTT as well as only inactivating mHTT without altering wild-type HTT or wild-type huntingtin protein (wtHTT) comes highly recommended, and may offer a promising treatment option for HD. Here, we reviewed the therapeutic approaches that allele-selective lowering mHTT expression by targeting only mutant HTT DNA, RNA and mHTT along with recent preclinical and clinical outcomes and challenges, in anticipation of some novel ideas to be introduced into HD therapeutic research.

Emerging pharmacological approaches for Huntington's disease

Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by cognitive, motor, and psychiatric symptoms. Despite significant advances in understanding the underlying molecular mechanisms of HD, there is currently no cure or disease-modifying treatment available. Emerging pharmacological approaches offer promising strategies to alleviate symptoms and slow down disease progression. This comprehensive review aims to provide a critical appraisal of the latest developments in pharmacological interventions for HD. The review begins by discussing the pathogenesis of HD, focusing on the role of mutant huntingtin protein, mitochondrial dysfunction, excitotoxicity, and neuro-inflammation. It then explores emerging therapeutic targets, including the modulation of protein homeostasis, mitochondrial function, neuro-inflammation, and neurotransmitter systems. Pharmacological agents targeting these pathways are discussed, including small molecules, gene-based therapies, and neuroprotective agents. In recent years, several clinical trials have been conducted to evaluate the safety and efficiency of novel compounds for HD. This review presents an update on the outcomes of these trials, highlighting promising results and challenges encountered. Additionally, it discusses the potential of repurposing existing drugs approved for other indications as a cost-effective approach for HD treatment. The review concludes by summarizing the current state of pharmacological approaches for HD and outlining future directions in drug development. The integration of multiple therapeutic strategies, personalized medicine approaches, and combination therapies are highlighted as potential avenues to maximize treatment effectiveness.

Extracellular vesicle and CRISPR gene therapy: Current applications in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Huntington's disease

Neurodegenerative diseases are characterized by progressive deterioration of the nervous system. Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD) are prominently life-threatening examples of neurodegenerative diseases. The complexity of the pathophysiology in neurodegenerative diseases causes difficulties in diagnosing. Although the drugs temporarily help to correct specific symptoms including memory loss and degeneration, a complete treatment has not been found yet. New therapeutic approaches have been developed to understand and treat the underlying pathogenesis of neurodegenerative diseases. With this purpose, clustered-regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) technology has recently suggested a new treatment option. Editing of the genome is carried out by insertion and deletion processes on DNA. Safe delivery of the CRISPR/Cas system to the targeted cells without affecting surrounding cells is frequently investigated. Extracellular vesicles (EVs), that is exosomes, have recently been used in CRISPR/Cas studies. In this review, CRISPR/Cas and EV approaches used for diagnosis and/or treatment in AD, PD, ALS, and HD are reviewed. CRISPR/Cas and EV technologies, which stand out as new therapeutic approaches, may offer a definitive treatment option in neurodegenerative diseases.

Genetic Risk, Inflammation, and Therapeutics: An Editorial Overview of Recent Advances in Aging Brains and Neurodegeneration

Neurodegenerative disorders, including Dementia, Parkinson's disease, various Vision disorders, Multiple sclerosis, and transsynaptic degenerative changes represent a significant challenge in aging populations. This editorial synthesizes and discusses recent advancements in understanding the genetic and environmental factors contributing to these diseases. Central to these advancements is the role of neuroinflammation and oxidative stress, which exacerbate neuronal damage and accelerate disease progression. Emerging research underscores the significance of mitochondrial dysfunction and protein aggregation in neurodegenerative pathology, highlighting shared mechanisms across various disorders. Innovative therapeutic strategies, including gene therapy, CRISPR-Cas technology, and the use of naturally occurring antioxidant molecules, are being investigated to target and manage these conditions. Additionally, lifestyle interventions such as exercise and healthy diet have shown promise in enhancing brain plasticity and reducing neuroinflammation. Advances in neuroimaging and biomarker discovery are necessary to improve early diagnosis, while clinical and preclinical studies are essential for the translation of these novel treatments. This edition aims to bridge the gap between molecular mechanisms and therapeutic applications, offering insights into potential interventions to mitigate the impact of neurodegenerative diseases. By establishing a deeper understanding of these complex processes, we aim to move closer to effective prevention and treatment strategies, ultimately improving the quality of life for those affected by neurodegenerative disorders.

Molecular Mechanisms in the Design of Novel Targeted Therapies for Neurodegenerative Diseases

Neurodegenerative diseases are a diverse group of diseases characterized by a progressive loss of neurological function due to damage to nerve cells in the central nervous system. In recent years, there has been a worldwide increase in the expanding associated with increasing human life expectancy. Molecular mechanisms control many of the essential life processes of cells, such as replication, transcription, translation, protein synthesis and gene regulation. These are complex interactions that form the basis for understanding numerous processes in the organism and developing new diagnostic and therapeutic approaches. In the context of neurodegenerative diseases, molecular basis refers to changes at the molecular level that cause damage to or degeneration of nerve cells. These may include protein aggregates leading to pathological structures in brain cells, impaired protein transport in nerve cells, mitochondrial dysfunction, inflammatory processes or genetic mutations that impair nerve cell function. New medical therapies are based on these mechanisms and include gene therapies, reduction in inflammation and oxidative stress, and the use of miRNAs and regenerative medicine. The aim of this study was to bring together the current state of knowledge regarding selected neurodegenerative diseases, presenting the underlying molecular mechanisms involved, which could be potential targets for new forms of treatment.

Correction of symptoms of Huntington disease by genistein through FOXO3-mediated autophagy stimulation

Huntington disease (HD) is a neurodegenerative disorder caused by a mutation in the HTT gene. The expansion of CAG triplets leads to the appearance of misfolded HTT (huntingtin) forming aggregates and leading to impairment of neuronal functions. Here we demonstrate that stimulation of macroautophagy/autophagy by genistein (4',5,7-trihydroxyisoflavone or 5,7-dihydroxy-3-(4-hydroxyphenyl)-4 H-1-benzopyran-4-one) caused a reduction of levels of mutated HTT in brains of HD mice and correction of their behavior as assessed in a battery of cognitive, anxiety and motor tests, even if the compound was administered after symptoms had developed in the animals. Biochemical and immunological parameters were also improved in HD mice. Studies on molecular mechanisms of genistein-mediated stimulation of autophagy in HD cells indicated the involvement of the FOXO3-related pathway. In conclusion, treatment with genistein stimulates the autophagy process in the brains of HD mice, leading to correction of symptoms of HD, suggesting that it might be considered as a potential drug for this disease. Combined with a very recently published report indicating that impaired autophagy may be a major cause of neurodegenerative changes, these results may indicate the way to the development of effective therapeutic approaches for different neurodegenerative diseases by testing compounds (or possibly combinations of compounds) capable of stimulating autophagy and/or unblocking this process.Abbreviations: CNS: central nervous system; EPM: elevated plus-maze; GOT1/ASPAT: glutamic-oxaloacetic transaminase 1, soluble; GPT/ALAT/ALT: glutamic pyruvic transaminase, soluble; HD: Huntington disease; HTT: huntingtin; IL: interleukin; mHTT: mutant huntingtin; NOR: novel object recognition; MWM: Morris water maze; OF: open field; ROS: reactive oxygen species; TNF: tumor necrosis factor.

CRISPR/Cas9 system and its applications in nervous system diseases

The clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) system is an acquired immune system of many bacteria and archaea, comprising CRISPR loci, Cas genes, and its associated proteins. This system can recognize exogenous DNA and utilize the Cas9 protein's nuclease activity to break DNA double-strand and to achieve base insertion or deletion by subsequent DNA repair. In recent years, multiple laboratory and clinical studies have revealed the therapeutic role of the CRISPR/Cas9 system in neurological diseases. This article reviews the CRISPR/Cas9-mediated gene editing technology and its potential for clinical application against neurological diseases.

Neurologic orphan diseases: Emerging innovations and role for genetic treatments

Orphan diseases are rare diseases that affect less than 200000 individuals within the United States. Most orphan diseases are of neurologic and genetic origin. With the current advances in technology, more funding has been devoted to developing therapeutic agents for patients with these conditions. In our review, we highlight emerging options for patients with neurologic orphan diseases, specifically including diseases resulting in muscular deterioration, epilepsy, seizures, neurodegenerative movement disorders, inhibited cognitive development, neuron deterioration, and tumors. After extensive literature review, gene therapy offers a promising route for the treatment of neurologic orphan diseases. The use of clustered regularly interspaced palindromic repeats/Cas9 has demonstrated positive results in experiments investigating its role in several diseases. Additionally, the use of adeno-associated viral vectors has shown improvement in survival, motor function, and developmental milestones, while also demonstrating reversal of sensory ataxia and cardiomyopathy in Friedreich ataxia patients. Antisense oligonucleotides have also been used in some neurologic orphan diseases with positive outcomes. Mammalian target of rapamycin inhibitors are currently being investigated and have reduced abnormal cell growth, proliferation, and angiogenesis. Emerging innovations and the role of genetic treatments open a new window of opportunity for the treatment of neurologic orphan diseases.

Untangling the Role of Tau in Huntington's Disease Pathology

There is increasing evidence for the presence of pathological forms of tau in tissues of both Huntington's disease (HD) patients and animal models of this condition. While cumulative studies of the past decade have led to the proposition that this disorder could also be considered a tauopathy, the implications of tau in cellular toxicity and consequent behavioral impairments are largely unknown. In fact, recent animal work has challenged the contributory role of tau in HD pathogenesis/pathophysiology. This review presents the supporting and opposing arguments for the involvement of tau in HD, highlighting the discrepancies that have emerged. Reflecting on what is known in other tauopathies, the putative mechanisms through which tau could initiate and/or contribute to pathology are discussed, shedding light on the future research directions that could be considered to confirm, or rule out, the clinical relevance of tau in HD.

Functional brain networks in the evaluation of patients with neurodegenerative disorders

Network analytical tools are increasingly being applied to brain imaging maps of resting metabolic activity (PET) or blood oxygenation-dependent signals (functional MRI) to characterize the abnormal neural circuitry that underlies brain diseases. This approach is particularly valuable for the study of neurodegenerative disorders, which are characterized by stereotyped spread of pathology along discrete neural pathways. Identification and validation of disease-specific brain networks facilitate the quantitative assessment of pathway changes over time and during the course of treatment. Network abnormalities can often be identified before symptom onset and can be used to track disease progression even in the preclinical period. Likewise, network activity can be modulated by treatment and might therefore be used as a marker of efficacy in clinical trials. Finally, early differential diagnosis can be achieved by simultaneously measuring the activity levels of multiple disease networks in an individual patient's scans. Although these techniques were originally developed for PET, over the past several years analogous methods have been introduced for functional MRI, a more accessible non-invasive imaging modality. This advance is expected to broaden the application of network tools to large and diverse patient populations.

Functional Intercellular Transmission of miHTT via Extracellular Vesicles: An In Vitro Proof-of-Mechanism Study

Huntington's disease (HD) is a fatal neurodegenerative disorder caused by GAG expansion in exon 1 of the huntingtin (HTT) gene. AAV5-miHTT is an adeno-associated virus serotype 5-based vector expressing an engineered HTT-targeting microRNA (miHTT). Preclinical studies demonstrate the brain-wide spread of AAV5-miHTT following a single intrastriatal injection, which is partly mediated by neuronal transport. miHTT has been previously associated with extracellular vesicles (EVs), but whether EVs mediate the intercellular transmission of miHTT remains unknown. A contactless culture system was used to evaluate the transport of miHTT, either from a donor cell line overexpressing miHTT or AAV5-miHTT transduced neurons. Transfer of miHTT to recipient (HEK-293T, HeLa, and HD patient-derived neurons) cells was observed, which significantly reduced HTT mRNA levels. miHTT was present in EV-enriched fractions isolated from culture media. Immunocytochemical and in situ hybridization experiments showed that the signal for miHTT and EV markers co-localized, confirming the transport of miHTT within EVs. In summary, we provide evidence that an engineered miRNA-miHTT-is loaded into EVs, transported across extracellular space, and taken up by neighboring cells, and importantly, that miHTT is active in recipient cells downregulating HTT expression. This represents an additional mechanism contributing to the widespread biodistribution of AAV5-miHTT.

Mn(II) Quinoline Complex (4QMn) Restores Proteostasis and Reduces Toxicity in Experimental Models of Huntington's Disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder, of the so-called minority diseases, due to its low prevalence. It is caused by an abnormally long track of glutamines (polyQs) in mutant huntingtin (mHtt), which makes the protein toxic and prone to aggregation. Many pathways of clearance of badly-folded proteins are disrupted in neurons of patients with HD. In this work, we show that one Mn(II) quinone complex (4QMn), designed to work as an artificial superoxide dismutase, is able to activate both the ubiquitin-proteasome system and the autophagy pathway in vitro and in vivo models of HD. Activation of these pathways degrades mHtt and other protein-containing polyQs, which restores proteostasis in these models. Hence, we propose 4QMn as a potential drug to develop a therapy to treat HD.

Non-Cell Autonomous and Epigenetic Mechanisms of Huntington's Disease

Huntington's disease (HD) is a rare neurodegenerative disorder caused by an expansion of CAG trinucleotide repeat located in the exon 1 of Huntingtin (HTT) gene in human chromosome 4. The HTT protein is ubiquitously expressed in the brain. Specifically, mutant HTT (mHTT) protein-mediated toxicity leads to a dramatic degeneration of the striatum among many regions of the brain. HD symptoms exhibit a major involuntary movement followed by cognitive and psychiatric dysfunctions. In this review, we address the conventional role of wild type HTT (wtHTT) and how mHTT protein disrupts the function of medium spiny neurons (MSNs). We also discuss how mHTT modulates epigenetic modifications and transcriptional pathways in MSNs. In addition, we define how non-cell autonomous pathways lead to damage and death of MSNs under HD pathological conditions. Lastly, we overview therapeutic approaches for HD. Together, understanding of precise neuropathological mechanisms of HD may improve therapeutic approaches to treat the onset and progression of HD.