A polymorphic DNA marker genetically linked to Huntington's disease

A novel specific PERK activator reduces toxicity and extends survival in Huntington's disease models

One of the pathways of the unfolded protein response, initiated by PKR-like endoplasmic reticulum kinase (PERK), is key to neuronal homeostasis in neurodegenerative diseases. PERK pathway activation is usually accomplished by inhibiting eIF2α-P dephosphorylation, after its phosphorylation by PERK. Less tried is an approach involving direct PERK activation without compromising long-term recovery of eIF2α function by dephosphorylation. Here we show major improvement in cellular (STHdh^Q111/111) and mouse (R6/2) Huntington's disease (HD) models using a potent small molecule PERK activator that we developed, MK-28. MK-28 showed PERK selectivity in vitro on a 391-kinase panel and rescued cells (but not PERK-/- cells) from ER stress-induced apoptosis. Cells were also rescued by the commercial PERK activator CCT020312 but MK-28 was significantly more potent. Computational docking suggested MK-28 interaction with the PERK activation loop. MK-28 exhibited remarkable pharmacokinetic properties and high BBB penetration in mice. Transient subcutaneous delivery of MK-28 significantly improved motor and executive functions and delayed death onset in R6/2 mice, showing no toxicity. Therefore, PERK activation can treat a most aggressive HD model, suggesting a possible approach for HD therapy and worth exploring for other neurodegenerative disorders.

Cortical Network Dynamics Is Altered in Mouse Models of Huntington's Disease

Huntington's disease (HD) is a neurodegenerative disorder characterized by involuntary movements, cognitive deficits, and psychiatric disturbances. Although evidence indicates that projections from motor cortical areas play a key role in the development of dysfunctional striatal activity and motor phenotype, little is known about the changes in cortical microcircuits and their role in the development of the HD phenotype. Here we used two-photon laser-scanning microscopy to evaluate network dynamics of motor cortical neurons in layers II/III in behaving transgenic R6/2 and knock-in Q175+/- mice. Symptomatic R6/2 mice displayed increased motion manifested by a significantly greater number of motion epochs, whereas symptomatic Q175 mice displayed decreased motion. In both models, calcium transients in symptomatic mice displayed reduced amplitude, suggesting decreased bursting activity. Changes in frequency were genotype- and time-dependent; for R6/2 mice, the frequency was reduced during both motion and nonmotion, whereas in symptomatic Q175 mice, the reduction only occurred during nonmotion. In presymptomatic Q175 mice, frequency was increased during both behavioral states. Interneuronal correlation coefficients were generally decreased in both models, suggesting disrupted interneuronal communication in HD cerebral cortex. These results indicate similar and contrasting effects of the HD mutation on cortical ensemble activity depending on mouse model and disease stage.

De-Novo Ligand Design against Mutated Huntington Gene by Ligand-based Pharmacophore Modeling Approach

Background:

Huntington's disease is characterized by three side effects, including motor disturbances, psychiatric elements, and intellectual weakness. The onset for HD has nonlinear converse associations with the number of repeat sequences of the polyglutamine mutations, so that younger patients have a tendency for longer repeats length. This HD variation is because of the development of a polyglutamine (CAG) repeats in the exon 1 of the Huntingtin protein.

Methods:

In the present study, a few derivatives utilized as a part of the treatment of HD, are used to create the pharmacophore model and based on the features of the pharmacophore model; an attempt is made to design the de-novo drug for the HD protein. HD protein structure was built and docked with the novel ligand, based on shared feature pharmacophore model, through a ligand-based pharmacophore modeling approach.

Results:

The novel ligand contains 1 HBAs, 2 HBDs, and 2 aromatic rings. It fulfills all the properties of certain drug-likeness rules, non-toxic in nature. In the docked complex, the common interactive amino acids identified are SER 1035, ALA 1062, MET 1068, LEU 1031, and THR 1036, which confirmed the validity and stability of a ligand molecule to be used as a drug in the treatment of Huntington’s disease.

Conclusion:

A novel ligand can be used in clinical trials as a drug molecule against the mutations of HD gene and in laboratory procedures for efficacy analysis.

Patient-reported impact of symptoms in Huntington disease: PRISM-HD

OBJECTIVE

To determine the frequency and relative importance of symptoms experienced by adults with Huntington disease (HD) and to identify factors associated with a higher disease burden.

METHODS

We performed 40 qualitative interviews (n = 20 with HD, n = 20 caregivers) and analyzed 2,082 quotes regarding the symptomatic burden of HD. We subsequently performed a cross-sectional study with 389 participants (n = 156 with HD [60 of whom were prodromal], n = 233 caregivers) to assess the prevalence and relative importance (scale 0-4) of 216 symptoms and 15 symptomatic themes in HD. Cross-correlation analysis was performed based on sex, disease duration, age, number of CAG repeats, disease burden, Total Functional Capacity score, employment status, disease status, and ambulatory status.

RESULTS

The symptomatic themes with the highest prevalence in HD were emotional issues (83.0%), fatigue (82.5%), and difficulty thinking (77.0%). The symptomatic themes with the highest relative importance to participants were difficulty thinking (1.91), impaired sleep or daytime sleepiness (1.90), and emotional issues (1.81). High Total Functional Capacity scores, being employed, and having prodromal HD were associated with a lower prevalence of symptomatic themes. Despite reporting no clinical features of the disease, prodromal individuals demonstrated high rates of emotional issues (71.2%) and fatigue (69.5%). There was concordance between the prevalence of symptoms reported by manifest individuals and caregivers.

CONCLUSIONS

Many symptomatic themes affect the lives of those with HD. These themes have a variable level of importance to the HD population and are identified both by those with HD and by their caregivers.

Association Between Toll-Like Receptor 4 (TLR4) and Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) Genetic Variants and Clinical Progression of Huntington's Disease

BACKGROUND

Although Huntington's disease (HD) is caused by a single dominant gene, it is clear that there are genetic modifiers that may influence the age of onset and disease progression.

OBJECTIVES

We sought to investigate whether new inflammation-related genetic variants may contribute to the onset and progression of HD.

METHODS

We first used postmortem brain material from patients at different stages of HD to look at the protein expression of toll-like receptor 4 (TLR4) and triggering receptor expressed on myeloid cells 2 (TREM2). We then genotyped the TREM2 R47H gene variant and 3 TLR4 single nucleotide polymorphisms in a large cohort of HD patients from the European Huntington's Disease Network REGISTRY.

RESULTS

We found an increase in the number of cells expressing TREM2 and TLR4 in postmortem brain samples from patients dying with HD. We also found that the TREM2 R47H gene variant was associated with changes in cognitive decline in the large cohort of HD patients, whereas 2 of 3 TLR4 single nucleotide polymorphisms assessed were associated with changes in motor progression in this same group.

CONCLUSIONS

These findings identify TREM2 and TLR4 as potential genetic modifiers for HD and suggest that inflammation influences disease progression in this condition. © 2019 International Parkinson and Movement Disorder Society.

Diphenyl diselenide protects a Caenorhabditis elegans model for Huntington's disease by activation of the antioxidant pathway and a decrease in protein aggregation

The effect of (PhSe)₂ in a C. elegans model for Huntington's disease. Treatment with (PhSe)₂ triggered the nuclear translocation and activation of DAF-16 transcription factor in C. elegans, inducing the expression of superoxide dismutase-3 (SOD-3) and heat shock protein-16.2 (HSP-16.2). SOD-3 acts on reactive oxygen species (ROS) detoxification, and HSP-16.2 decreases protein misfolding and aggregation, which occur in HD.

Erucic acid, a nutritional PPARδ-ligand may influence Huntington's disease pathogenesis

Increasing recent evidence suggests a key role of oligodendroglial injury and demyelination in the pathophysiology of Huntington's Disease (HD) and the transcription factor PPARδ is critical for oligodendroglial regeneration and myelination. PPARδ directly involves in the pathogenesis of HD and treatment with a brain-permeable PPARδ-agonist (KD3010) alleviates its severity in mice. Erucic acid (EA) is also a PPARδ-ligand ω9 fatty acid which is highly consumed in Asian countries through ingesting cruciferous vegetables such as rapeseed (Brassica napus) and indian mustard (Brassica juncea). EA is also an ingredient of Lorenzo's oil employed in the medical treatment of adrenoleukodystrophy and can be converted to nervonic acid, a component of myelin. HD pathogenesis also involves oxidative and inflammatory injury and EA exerts antioxidative and antiinflammatory efficacies including inhibition of thrombin and elastase. Consumption of rapeseed, indian mustard, and Canola oils (containing EA) improves cognitive parameters in animal models, as well as treatment with pure EA. Moreover, erucamide, an endogenous EA-amide derivative regulating angiogenesis and water balance, exerts antidepressive and anxiolytic effects in mice. Hitherto, no study has investigated the therapeutic potential of EA in HD and we believe that it strongly merits to be studied in animal models of HD as a potential therapeutic.

Autophagic and endo-lysosomal dysfunction in neurodegenerative disease

Due to their post-mitotic state, metabolic demands and often large polarised morphology, the function and survival of neurons is dependent on an efficient cellular waste clearance system both for generation of materials for metabolic processes and removal of toxic components. It is not surprising therefore that deficits in protein clearance can tip the balance between neuronal health and death. Here we discuss how autophagy and lysosome-mediated degradation pathways are disrupted in several neurological disorders. Both genetic and cell biological evidence show the diversity and complexity of vesicular clearance dysregulation in cells, and together may ultimately suggest a unified mechanism for neuronal demise in degenerative conditions. Causative and risk-associated mutations in Alzheimer's disease, Frontotemporal Dementia, Amyotrophic Lateral Sclerosis, Parkinson's disease, Huntington's disease and others have given the field a unique mechanistic insight into protein clearance processes in neurons. Through their broad implication in neurodegenerative diseases, molecules involved in these genetic pathways, in particular those involved in autophagy, are emerging as appealing therapeutic targets for intervention in neurodegeneration.

Brain Microbiota in Huntington's Disease Patients

One of the most important challenges facing medical science is to better understand the cause of neuronal pathology in neurodegenerative diseases. Such is the case for Huntington's disease (HD), a genetic disorder primarily caused by a triplet expansion in the Huntingtin gene (HTT). Although aberrant HTT is expressed from embryogenesis, it remains puzzling as to why the onset of disease symptoms manifest only after several decades of life. In the present study, we investigated the possibility of microbial infection in brain tissue from patients with HD, reasoning that perhaps mutated HTT could be deleterious for immune cells and neural tissue, and could facilitate microbial colonization. Using immunohistochemistry approaches, we observed a variety of fungal structures in the striatum and frontal cortex of seven HD patients. Some of these fungi were found in close proximity to the nucleus, or even as intranuclear inclusions. Identification of the fungal species was accomplished by next-generation sequencing (NGS). Interestingly, some genera, such as Ramularia, appeared unique to HD patients, and have not been previously described in other neurodegenerative diseases. Several bacterial species were also identified both by PCR and NGS. Notably, a curved and filamentous structure that immunoreacts with anti-bacterial antibodies was characteristic of HD brains and has not been previously observed in brain tissue from neurodegenerative patients. Prevalent bacterial genera included Pseudomonas, Acinetobacter, and Burkholderia. Collectively, our results represent the first attempt to identify the brain microbiota in HD. Our observations suggest that microbial colonization may be a risk factor for HD and might explain why the onset of the disease appears after several decades of life. Importantly, they may open a new field of investigation and could help in the design of new therapeutic strategies for this devastating disorder.

Confidential genetic testing and electronic health records: A survey of current practices among Huntington disease testing centers

Background

Clinical care teams providing presymptomatic genetic testing often employ advanced confidentiality practices for documentation and result storage. However, patient requests for increased confidentiality may be in conflict with the legal obligations of medical providers to document patient care activities in the electronic health record (EHR). Huntington disease presents a representative case study for investigating the ways centers currently balance the requirements of EHRs with the privacy demands of patients seeking presymptomatic genetic testing.

Methods

We surveyed 23 HD centers (53% response rate) regarding their use of the EHR for presymptomatic HD testing.

Results

Our survey revealed that clinical care teams and laboratories have each developed their own practices, which are cumbersome and often include EHR avoidance. We found that a majority of HD care teams record appointments in the EHR (91%), often using vague notes. Approximately half of the care teams (52%) keep presymptomatic results of out of the EHR.

Conclusion

As genetic knowledge grows, linking more genes to late‐onset conditions, institutions will benefit from having professional recommendations to guide development of policies for EHR documentation of presymptomatic genetic results. Policies must be sensitive to the ethical differences and patient demands for presymptomatic genetic testing compared to those undergoing confirmatory genetic testing.

Lack of mutant huntingtin in cortical efferents improves behavioral inflexibility and corticostriatal dynamics in Huntington's disease mice

Abnormal communication between cerebral cortex and striatum plays a major role in the motor symptoms of Huntington's disease (HD), a neurodegenerative disorder caused by a mutation of the huntingtin gene (mHTT). Because cortex is the main driver of striatal processing, we recorded local field potential (LFP) activity simultaneously in primary motor cortex (M1) and dorsal striatum (DS) in BACHD mice, a full-length HD gene model, and in a conditional BACHD/Emx-1 Cre (BE) model in which mHTT is suppressed in cortical efferents, while mice freely explored a plus-shaped maze beginning at 20 wk of age. Relative to wild-type (WT) controls, BACHD mice were just as active across >40 wk of testing but became progressively less likely to turn into a perpendicular arm as they approached the choice point of the maze, a sign of HD motor inflexibility. BE mice, in contrast, turned as freely as WT throughout testing. Although BE mice did not exactly match WT in LFP activity, the reduction in alpha (8-13 Hz), beta (13-30 Hz), and low-gamma (30-50 Hz) power that occurred in M1 of turning-impaired BACHD mice was reversed. No reversal occurred in DS. In fact, BE mice showed further reductions in DS theta (4-8 Hz), beta, and low-gamma power relative to the BACHD model. Coherence analysis indicated a dysregulation of corticostriatal information flow in both BACHD and BE mice. Collectively, our results suggest that mHTT in cortical outputs drives the dysregulation of select cortical frequencies that accompany the loss of behavioral flexibility in HD.NEW & NOTEWORTHY BACHD mice, a full-length genetic model of Huntington's disease (HD), express aberrant local field potential (LFP) activity in primary motor cortex (M1) along with decreased probability of turning into a perpendicular arm of a plus-shaped maze, a motor inflexibility phenotype. Suppression of the mutant huntingtin gene in cortical output neurons prevents decline in turning and improves alpha, beta, and low-gamma activity in M1. Our results implicate cortical networks in the search for therapeutic strategies to alleviate HD motor signs.

The Role of Microglia and Astrocytes in Huntington's Disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease. HD patients present with movement disorders, behavioral and psychiatric symptoms and cognitive decline. This review summarizes the contribution of microglia and astrocytes to HD pathophysiology. Neuroinflammation in the HD brain is characterized by a reactive morphology in these glial cells. Microglia and astrocytes are critical in regulating neuronal activity and maintaining an optimal milieu for neuronal function. Previous studies provide evidence that activated microglia and reactive astrocytes contribute to HD pathology through transcriptional activation of pro-inflammatory genes to perpetuate a chronic inflammatory state. Reactive astrocytes also display functional changes in glutamate and ion homeostasis and energy metabolism. Astrocytic and microglial changes may further contribute to the neuronal death observed with the progression of HD. Importantly, the degree to which these neuroinflammatory changes are detrimental to neurons and contribute to the progression of HD pathology is not well understood. Furthermore, recent observations provide compelling evidence that activated microglia and astrocytes exert a variety of beneficial functions that are essential for limiting tissue damage and preserving neuronal function in the HD brain. Therefore, a better understanding of the neuroinflammatory environment in the brain in HD may lead to the development of targeted and innovative therapeutic opportunities.

From Many to One to Many-the Search for Causes of Psychiatric Illness

The search for the causes of medical and psychiatric disorders has gone through 3 historical phases. First, up until the mid-19th century, causes of illness were anecdotally recorded from individual cases, resulting in long and diverse lists for all disorders. Second, in the latter half of the 19th century, with the use of microbiological methods, single causes were found for many infectious diseases that led to specific diagnostic tests, effective preventions, and, in some cases, treatments. Causal thinking in medicine shifted from the earlier multicausal approaches to monocausal theories of etiology. Indeed, proving monocausal etiology became a way to establish the legitimacy of a disorder. Through the writings of Kahlbaum and Hecker, psychiatry was deeply influenced by this monocausal perspective, the importance of which was substantially amplified by a twist of fate: the increasing clinical importance of general paresis of the insane throughout the 19th century and the eventual proof that it too was a monocausal condition. However, in the mid-20th century, the third phase began. With decreasing deaths from infectious diseases, epidemiology and clinical medicine shifted to a chronic disease model in which paradigmatic disorders, such as cancer and cardiovascular disease, were shown to be highly multicausal. Biostatistics evolved from deterministic to probabilistic models of disease risk factors. Paradoxically, at this time, biological psychiatry, then rising to dominance in American psychiatry, vigorously pursued monocausal theories, first of neurochemical origin and then of genetic origin. We were trying to establish the legitimacy of our field by pursuing an outmoded model-that "real" diseases are monocausal. Despite ample evidence to the contrary, monocausal thinking continues to influence our field, for example, in the popular but improbable view that we can, with a few key advances, move easily from descriptive to etiologically based diagnoses.

Mutant Huntingtin Affects Diabetes and Alzheimer's Markers in Human and Cell Models of Huntington's Disease

A higher incidence of diabetes was observed among family members of individuals affected by Huntington's Disease with no follow-up studies investigating the genetic nature of the observation. Using a genome-wide association study (GWAS), RNA sequencing (RNA-Seq) analysis and western blotting of Rattus norvegicus and human, we were able to identify that the gene family of sortilin receptors was affected in Huntington's Disease patients. We observed that less than 5% of SNPs were of statistical significance and that sortilins and HLA/MHC gene expression or SNPs were associated with mutant huntingtin (mHTT). These results suggest that ST14A cells derived from R. norvegicus are a reliable model of HD, since sortilins were identified through analysis of the transcriptome in these cells. These findings help highlight the genes involved in mechanisms targeted by diabetes drugs, such as glucose transporters as well as proteins controlling insulin release related to mHTT. To the best of our knowledge, this is the first GWAS using RNA-Seq data from both ST14A rat HD cell model and human Huntington's Disease.

Closing the 'phenotype gap' in precision medicine: improving what we measure to understand complex disease mechanisms

The central concept underlying precision medicine is a mechanistic understanding of each disease and its response to therapy sufficient to direct a specific intervention. To execute on this vision requires parsing incompletely defined disease syndromes into discrete mechanistic subsets and developing interventions to precisely address each of these etiologically distinct entities. This will require substantial adjustment of traditional paradigms which have tended to aggregate high-level phenotypes with very different etiologies. In the current environment, where diagnoses are not mechanistic, drug development has become so expensive that it is now impractical to imagine the cost-effective creation of new interventions for many prevalent chronic conditions. The vision of precision medicine also argues for a much more seamless integration of research and development with clinical care, where shared taxonomies will enable every clinical interaction to inform our collective understanding of disease mechanisms and drug responses. Ideally, this would be executed in ways that drive real-time and real-world discovery, innovation, translation, and implementation. Only in oncology, where at least some of the biology is accessible through surgical excision of the diseased tissue or liquid biopsy, has "co-clinical" modeling proven feasible. In most common germline disorders, while genetics often reveal the causal mutations, there still remain substantial barriers to efficient disease modeling. Aggregation of similar disorders under single diagnostic labels has directly contributed to the paucity of etiologic and mechanistic understanding by directly reducing the resolution of any subsequent studies. Existing clinical phenotypes are typically anatomic, physiologic, or histologic, and result in a substantial mismatch in information content between the phenomes in humans or in animal 'models' and the variation in the genome. This lack of one-to-one mapping of discrete mechanisms between disease and animal models causes a failure of translation and is one form of 'phenotype gap.' In this review, we will focus on the origins of the phenotyping deficit and approaches that may be considered to bridge the gap, creating shared taxonomies between human diseases and relevant models, using cardiovascular examples.

The Era of the Genome and Dental Medicine

Understanding the "code of life" and mapping the human genome have been monumental and era-defining scientific landmarks-analogous to setting foot on the moon. The last century has been characterized by exponential advances in our understanding of the biological and specifically molecular basis of health and disease. The early part of the 20th century was marked by fundamental theoretical and scientific advances in understanding heredity, the identification of the DNA molecule and genes, and the elucidation of the central dogma of biology. The second half was characterized by experimental and increasingly molecular investigations, including clinical and population applications. The completion of the Human Genome Project in 2003 and the continuous technological advances have democratized access to this information and the ability to generate health and disease association data; however, the realization of genomic and precision medicine, to practically improve people's health, has lagged. The oral health domain has made great strides and substantially benefited from the last century of advances in genetics and genomics. Observations regarding a hereditary component of dental caries were reported as early as the 1920s. Subsequent breakthroughs were made in the discovery of genetic causes of rare diseases, such as ectodermal dysplasias, orofacial clefts, and other craniofacial and dental anomalies. More recently, genome-wide investigations have been conducted and reported for several diseases and traits, including periodontal disease, dental caries, tooth agenesis, cancers of the head and neck, orofacial pain, temporomandibular disorders, and craniofacial morphometrics. Gene therapies and gene editing with CRISPR/Cas represent the latest frontier surpassed in the era of genomic medicine. Amid rapid genomics progress, several challenges and opportunities lie ahead. Importantly, systematic efforts supported by implementation science are needed to realize the full potential of genomics, including the improvement of public and practitioner genomics literacy, the promotion of individual and population oral health, and the reduction of disparities.

Demonstration of prion-like properties of mutant huntingtin fibrils in both in vitro and in vivo paradigms

In recent years, evidence has accumulated to suggest that mutant huntingtin protein (mHTT) can spread into healthy tissue in a prion-like fashion. This theory, however, remains controversial. To fully address this concept and to understand the possible consequences of mHTT spreading to Huntington’s disease pathology, we investigated the effects of exogenous human fibrillar mHTT (Q48) and huntingtin (HTT) (Q25) N-terminal fragments in three cellular models and three distinct animal paradigms. For in vitro experiments, human neuronal cells [induced pluripotent stem cell-derived GABA neurons (iGABA) and (SH-SY5Y)] as well as human THP1-derived macrophages, were incubated with recombinant mHTT fibrils. Recombinant mHTT and HTT fibrils were taken up by all cell types, inducing cell morphology changes and death. Variations in HTT aggregation were further observed following incubation with fibrils in both THP1 and SH-SY5Y cells. For in vivo experiments, adult wild-type (WT) mice received a unilateral intracerebral cortical injection and R6/2 and WT pups were administered fibrils via bilateral intraventricular injections. In both protocols, the injection of Q48 fibrils resulted in cognitive deficits and increased anxiety-like behavior. Post-mortem analysis of adult WT mice indicated that most fibrils had been degraded/cleared from the brain by 14 months post-surgery. Despite the absence of fibrils at these later time points, a change in the staining pattern of endogenous HTT was detected. A similar change was revealed in post-mortem analysis of the R6/2 mice. These effects were specific to central administration of fibrils, as mice receiving intravenous injections were not characterized by behavioral changes. In fact, peripheral administration resulted in an immune response mounting against the fibrils. Together, the in vitro and in vivo data indicate that exogenously administered mHTT is capable of both causing and exacerbating disease pathology.

New Therapeutic Approaches for the Treatment of Huntington’s Disease

The use of transplantation (TR) of fetal neural tissue as a therapeutic method started much later in patients suffering from Huntington’s disease (HD) than in those with Parkinson’s disease. The clinical trial, following a wide range of animal experiments (neurotoxic models and newly also transgenic mice), includes about 30 HD patients until now. Because of limited use of the human fetal tissue by ethical and technical concerns, there is necessity to search for the alternative sources for neural grafting. The first attempt with xenotransplantation (in 12 HD patients) and with TR of encapsulated genetically modified cells (in 6 HD patients) was performed, but no appreciable improvement of status in any of those patients was noted. Since no effective pharmacological treatment of HD is available, the TR of fetal neural tissue is now the only therapeutic approach which provides a reduction of symptoms in most of grafted patients. The possibilities are enormous offered by neural stem cells, optionally by embryonic stem cells, which could be expanded in cultures, cloned or genetically modified and then grafted into the patient’s brain. On the other hand, the neural progenitor and stem cells, normally present within the subependymal layer of the lateral brain ventricles also in adulthood, might be induced to become an endogenous source of glia and neurons participating in the brain’s repair.

EGF Treatment Improves Motor Behavior and Cortical GABAergic Function in the R6/2 Mouse Model of Huntington's Disease

Recent evidence indicates that disruption of epidermal growth factor (EGF) signaling by mutant huntingtin (polyQ-htt) may contribute to the onset of behavioral deficits observed in Huntington's disease (HD) through a variety of mechanisms, including cerebrovascular dysfunction. Yet, whether EGF signaling modulates the development of HD pathology and the associated behavioral impairments remain unclear. To gain insight on this issue, we used the R6/2 mouse model of HD to assess the impact of chronic EGF treatment on behavior, and cerebrovascular and cortical neuronal functions. We found that bi-weekly treatment with a low dose of EGF (300 µg/kg, i.p.) for 6 weeks was sufficient to effectively improve motor behavior in R6/2 mice and diminish mortality, compared to vehicle-treated littermates. These beneficial effects of EGF treatment were dissociated from changes in cerebrovascular leakiness, a result that was surprising given that EGF ameliorates this deficit in other neurodegenerative diseases. Rather, the beneficial effect of EGF on R6/2 mice behavior was concomitant with a marked amelioration of cortical GABAergic function. As GABAergic transmission in cortical circuits is disrupted in HD, these novel data suggest a potential mechanistic link between deficits in EGF signaling and GABAergic dysfunction in the progression of HD.

100 Years of evolving gene-disease complexities and scientific debutants

It's been over 100 years since the word `gene' is around and progressively evolving in several scientific directions. Time-to-time technological advancements have heavily revolutionized the field of genomics, especially when it's about, e.g. triple code development, gene number proposition, genetic mapping, data banks, gene-disease maps, catalogs of human genes and genetic disorders, CRISPR/Cas9, big data and next generation sequencing, etc. In this manuscript, we present the progress of genomics from pea plant genetics to the human genome project and highlight the molecular, technical and computational developments. Studying genome and epigenome led to the fundamentals of development and progression of human diseases, which includes chromosomal, monogenic, multifactorial and mitochondrial diseases. World Health Organization has classified, standardized and maintained all human diseases, when many academic and commercial online systems are sharing information about genes and linking to associated diseases. To efficiently fathom the wealth of this biological data, there is a crucial need to generate appropriate gene annotation repositories and resources. Our focus has been how many gene-disease databases are available worldwide and which sources are authentic, timely updated and recommended for research and clinical purposes. In this manuscript, we have discussed and compared 43 such databases and bioinformatics applications, which enable users to connect, explore and, if possible, download gene-disease data.

Inorganic polyphosphate, a multifunctional polyanionic protein scaffold

Polyphosphate (polyP) consists of a linear arrangement of inorganic phosphates and defies its structural simplicity with an astounding number of different activities in the cell. Already well known for its ability to partake in phosphate, calcium, and energy metabolism, polyP recently gained a new functional dimension with the discovery that it serves as a stabilizing scaffold for protein-folding intermediates. In this review, we summarize and discuss the recent studies that have identified polyP not only as a potent protein-like chaperone that protects cells against stress-induced protein aggregation, but also as a robust modifier of amyloidogenic processes that shields neuronal cells from amyloid toxicity. We consider some of the most pressing questions in the field, the obstacles faced, and the potential avenues to take to provide a complete picture about the working mechanism and physiological relevance of this intriguing biopolymer.

Now Is the Time to Use Molecular Gene Testing for the Diagnosis of Primary Immune Deficiencies

The discovery of chromosomes, genes, and DNA in the early 20th century paved the way for the development of techniques to examine the role of these elements in disease pathogenesis. Since the start of the 21st century, genetic testing and particularly next-generation sequencing has allowed for a rapid rate of gene disease associations for a broad range of primary immunodeficiency patients. At the same time, biologic and small molecule-based therapies targeting specific molecular pathways have been developed and are being applied clinically and in research settings to treat genetically defined immunodeficiencies. In recent years, both the American Academy of Allergy Asthma and Immunology and the Clinical Immunology Society have recommended the use of genetic testing for diagnosis, therapy guidance, and genetic counseling in patients with clinical symptoms of primary immunodeficiency.

Mitochondrial alterations accompanied by oxidative stress conditions in skin fibroblasts of Huntington's disease patients

Huntington disease (HD) is an autosomal dominant neurodegenerative disorder manifesting as progressive impairment of motor function and different neuropsychiatric symptoms caused by an expansion of CAG repeats in huntingtin gene (HTT). Mitochondrial dysfunction and bioenergetic defects can contribute to the course of the disease, however, the molecular mechanism underlying this process is still largely unknown. In this study, we aimed to determine several mitochondrial parameters in HD fibroblasts and assess their relevance to the disease progression as well as to value mitochondrial pathology in peripheral cells as disease potential biomarker. We showed that HD fibroblasts demonstrate significantly lower growth rate compared to control fibroblasts despite the lack of cell cycle perturbations. In order to investigate mitochondrial contribution to cell growth differences between HD and healthy cells, we provided insight into various mitochondrial parameters. Conducted experiments have revealed a significant reduction of the ATP level in HD fibroblasts accompanied by a decrease in mitochondrial metabolic activity in relation to the cells from healthy donors. Importantly, there were no differences in the mitochondrial membrane potential (mtΔΨ) and OXPHOS complexes' levels. Slightly increased level of mitochondrial superoxide (mt. O2•-), but not cytosolic reactive oxygen species (cyt. ROS), has been demonstrated. We have also observed significantly elevated levels of some antioxidant enzymes (SOD2 and GR) which may serve as an indicator of antioxidant defense system in HD patients. Thus, we suggest that mitochondrial alterations in skin fibroblasts of Huntington's disease patients might be helpful in searching for novel disease biomarkers.

An active cognitive lifestyle as a potential neuroprotective factor in Huntington's disease

A cognitive stimulating lifestyle has been observed to confer cognitive benefits in multiple neurodegenerative diseases. However, the underlying neurobiological basis of this phenomenon remains unclear. Huntington's disease can provide a suitable model to study the effects and neural mechanisms of cognitive engagement in neurodegeneration. In this study, we investigate the effect of lifestyle factors such as education, occupation and engagement in cognitive activities in Huntington's disease gene carriers on cognitive performance and age of onset as well as the underlying neural changes sustaining these effects, measured by magnetic resonance imaging. Specifically, we analyzed both gray matter volume and the strength of connectivity of the executive control resting-state network. High levels of cognitive engagement were significantly associated with more preserved executive functions, a delay in the appearance of symptoms, reduced volume loss of the left precuneus and the bilateral caudate and a modulation of connectivity strength of anterior cingulate cortex and left angular gyrus with the executive control network. These findings suggest that a cognitively stimulating lifestyle may promote brain maintenance by modulating the executive control resting-state network and conferring protection against neurodegeneration, which results in a delayed onset of symptoms and improved performance in executive functions.

Complete but not partial inhibition of glutamate transporters exacerbates cortical excitability in the R6/2 mouse model of Huntington's disease

AIM

Deficient glutamate reuptake occurs in the cerebral cortex of Huntington's disease (HD) patients and murine models. Here, we examine the effects of partial or complete blockade of glutamate transporters on excitatory postsynaptic currents (EPSCs) of cortical pyramidal neurons (CPNs).

METHODS

Whole-cell patch clamp recordings of CPNs in slices from symptomatic R6/2 mice and wild-type (WT) littermates were used to examine the effects of selective or concurrent inhibition of glutamate reuptake transporters.

RESULTS

Selective inhibition of the glial glutamate transporter 1 (GLT-1) or the glutamate aspartate transporter (GLAST) produced slight decreases in decay time of evoked EPSCs in CPNs from WT and R6/2 mice with no significant differences between genotypes. In contrast, concurrent inhibition of both transporters with DL-TBOA induced a significant increase in area and decay time and this effect was significantly greater in R6/2 CPNs. Furthermore, full blockade also reduced spontaneous EPSC frequency and exacerbated epileptiform activity in CPNs from symptomatic R6/2 mice.

CONCLUSIONS

R6/2 CPNs are more sensitive to glutamate accumulation during full inhibition of both glutamate transporters, and these neurons have homeostatic mechanisms to cope with inhibition of GLT-1 or GLAST by a mechanism that involves upregulation of either transporter when the other is deficient.

Huntington's disease: Neuropsychiatric manifestations of Huntington's disease

OBJECTIVES

Huntington's disease (HD) is a profoundly incapacitating, and ultimately fatal, neurodegenerative disease. HD is presently incurable, so the current goal is to allow affected individuals to live as well as possible with the illness, to maximise functional independence and quality of life for the person with HD, their carers and family members. This clinical update review focuses on the common neuropsychiatric manifestations in HD, and outlines and evaluates the various neuropsychiatric facets of HD, including the aetiology, symptoms and diagnosis.

CONCLUSIONS

Neuropsychiatric symptoms can precede the classic motor clinical symptoms of HD (prodromal HD) by decades, and cause significant functional impairment. HD provides key insights and understanding into the organic psychiatric disorders, including contemporary clinical insights into the process of neurodegeneration and manifestation of neuropsychiatric symptoms.

RNA Related Pathology in Huntington's Disease

This chapter summarises research investigating the expression of huntingtin sense and anti-sense transcripts, the effect of the mutation on huntingtin processing as well as the more global effect of the mutation on the coding and non-coding transcriptomes. The huntingtin gene is ubiquitously expressed, although expression levels vary between tissues and cell types. A SNP that affects NF-ĸB binding in the huntingtin promoter modulates the expression level of huntingtin transcripts and is associated with the age of disease onset. Incomplete splicing between exon 1 and exon 2 has been shown to result in the expression of a small polyadenylated mRNA that encodes the highly pathogenic exon 1 huntingtin protein. This occurs in a CAG-repeat length dependent manner in all full-length mouse models of HD as well as HD patient post-mortem brains and fibroblasts. An antisense transcript to huntingtin is generated that contains a CUG repeat that is expanded in HD patients. In myotonic dystrophy, expanded CUG repeats form RNA foci in cell nuclei that bind specific proteins (e.g. MBL1). Short, pure CAG RNAs of approximately 21 nucleotides that have been processed by DICER can inhibit the translation of other CAG repeat containing mRNAs. The HD mutation affects the transcriptome at the level of mRNA expression, splicing and the expression of non-coding RNAs. Finally, expanded repetitive stretched of nucleotides can lead to RAN translation, in which the ribosome translates from the expanded repeat in all possible reading frames, producing proteins with various poly-amino acid tracts. The extent to which these events contribute to HD pathogenesis is largely unknown.

Huntington's disease-like disorders in Latin America and the Caribbean

Diseases with a choreic phenotype can be due to a variety of genetic etiologies. As testing for Huntington's disease (HD) becomes more available in previously resource-limited regions, it is becoming apparent that there are patients in these areas with other rare genetic conditions which cause an HD-like phenotype. Documentation of the presence of these conditions is important in order to provide appropriate diagnostic and clinical care for these populations. Information for this article was gathered in two ways; the literature was surveyed for publications reporting a variety of genetic choreic disorders, and movement disorders specialists from countries in Latin America and the Caribbean were contacted regarding their experiences with chorea of genetic etiology. Here we discuss the availability of molecular diagnostics for HD and for other choreic disorders, along with a summary of the published reports of affected subjects, and authors' personal experiences from the regions. While rare, patients affected by non-HD genetic choreas are evidently present in Latin America and the Caribbean. HD-like 2 is particularly prevalent in countries where the population has African ancestry. The incidence of other conditions is likely determined by other variations in ethnic background and settlement patterns. As genetic resources and awareness of these disorders improve, more patients are likely to be identified, and have the potential to benefit from education, support, and ultimately molecular therapies.

Population-specific genetic modification of Huntington's disease in Venezuela

Modifiers of Mendelian disorders can provide insights into disease mechanisms and guide therapeutic strategies. A recent genome-wide association (GWA) study discovered genetic modifiers of Huntington's disease (HD) onset in Europeans. Here, we performed whole genome sequencing and GWA analysis of a Venezuelan HD cluster whose families were crucial for the original mapping of the HD gene defect. The Venezuelan HD subjects develop motor symptoms earlier than their European counterparts, implying the potential for population-specific modifiers. The main Venezuelan HD family inherits HTT haplotype hap.03, which differs subtly at the sequence level from European HD hap.03, suggesting a different ancestral origin but not explaining the earlier age at onset in these Venezuelans. GWA analysis of the Venezuelan HD cluster suggests both population-specific and population-shared genetic modifiers. Genome-wide significant signals at 7p21.2-21.1 and suggestive association signals at 4p14 and 17q21.2 are evident only in Venezuelan HD, but genome-wide significant association signals at the established European chromosome 15 modifier locus are improved when Venezuelan HD data are included in the meta-analysis. Venezuelan-specific association signals on chromosome 7 center on SOSTDC1, which encodes a bone morphogenetic protein antagonist. The corresponding SNPs are associated with reduced expression of SOSTDC1 in non-Venezuelan tissue samples, suggesting that interaction of reduced SOSTDC1 expression with a population-specific genetic or environmental factor may be responsible for modification of HD onset in Venezuela. Detection of population-specific modification in Venezuelan HD supports the value of distinct disease populations in revealing novel aspects of a disease and population-relevant therapeutic strategies.

Salivary levels of total huntingtin are elevated in Huntington's disease patients

Patients with Huntington's disease (HD), an autosomal-dominant neurodegenerative disease, show substantial variability in age-of-onset, symptom severity and course of illness, warranting the need for biomarkers to anticipate and monitor these features. The HD gene encodes the disease protein huntingtin (Htt), a potentially useful biomarker for this disease. In the current study, we determined whether total Htt protein (normal plus mutant; "tHtt") could be reliably measured in human saliva, a body fluid that is much more accessible compared to cerebral spinal fluid or even blood, and whether salivary levels of tHtt were clinically meaningful. We collected 146 saliva samples from manifest HD patients, early-premanifest individuals, late-premanifest patients, gene-negative family members and normal controls. We found that tHtt protein could be reliably and stably detected in human saliva and that tHtt levels were significantly increased in saliva from HD individuals compared to normal controls. Salivary tHtt showed no gender effects, nor were levels correlated with total protein levels in saliva. Salivary tHtt was significantly positively correlated with age, but not age-of-onset or CAG-repeat length. Importantly, salivary tHtt was significantly correlated with several clinical measures, indicating relevance to disease symptom onset and/or severity. Measurements of salivary tHtt offer significant promise as a relevant, non-invasive disease biomarker for HD, and its use could be implemented into clinical applications.

The Post-GWAS Era: From Association to Function

During the past 12 years, genome-wide association studies (GWASs) have uncovered thousands of genetic variants that influence risk for complex human traits and diseases. Yet functional studies aimed at delineating the causal genetic variants and biological mechanisms underlying the observed statistical associations with disease risk have lagged. In this review, we highlight key advances in the field of functional genomics that may facilitate the derivation of biological meaning post-GWAS. We highlight the evidence suggesting that causal variants underlying disease risk often function through regulatory effects on the expression of target genes and that these expression effects might be modest and cell-type specific. We moreover discuss specific studies as proof-of-principle examples for current statistical, bioinformatic, and empirical bench-based approaches to downstream elucidation of GWAS-identified disease risk loci.

Huntington Disease: Genetics, Prevention, and Therapy Approaches

Huntington's chorea or Huntington disease (HD) is a late-onset autosomal dominant neurodegenerative disorder caused by a trinucleotide repeat expansion. The multidisciplinary study of HD has been the focus of an international collaborating effort of basic and applied research for several decades. HD was the first human genetic disease mapped using linkage analysis of DNA polymorphisms and became a paradigm for scores of genes mapped in the same manner. Presymptomatic and prenatal testing have been available for HD families in the last 30 years, following genetic counseling and careful bioethical guidelines. Nevertheless, with the cure for the disease still elusive the uptake of predictive testing by at risk individuals is low. Current treatment of HD is mostly symptomatic, but ongoing observational studies, clinical trials and development of new gene silencing technologies have provided hopeful results.

Clinical Neurology and Epidemiology of the Major Neurodegenerative Diseases

Neurodegenerative diseases are a common cause of morbidity and cognitive impairment in older adults. Most clinicians who care for the elderly are not trained to diagnose these conditions, perhaps other than typical Alzheimer's disease (AD). Each of these disorders has varied epidemiology, clinical symptomatology, laboratory and neuroimaging features, neuropathology, and management. Thus, it is important that clinicians be able to differentiate and diagnose these conditions accurately. This review summarizes and highlights clinical aspects of several of the most commonly encountered neurodegenerative diseases, including AD, frontotemporal dementia (FTD) and its variants, progressive supranuclear palsy (PSP), corticobasal degeneration (CBD), Parkinson's disease (PD), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and Huntington's disease (HD). For each condition, we provide a brief overview of the epidemiology, defining clinical symptoms and diagnostic criteria, relevant imaging and laboratory features, genetics, pathology, treatments, and differential diagnosis.

Salivary biomarkers for the diagnosis and monitoring of neurological diseases

Current research efforts on neurological diseases are focused on identifying novel disease biomarkers to aid in diagnosis, provide accurate prognostic information and monitor disease progression. With advances in detection and quantification methods in genomics, proteomics and metabolomics, saliva has emerged as a good source of samples for detection of disease biomarkers. Obtaining a sample of saliva offers multiple advantages over the currently tested biological fluids as it is a non-invasive, painless and simple procedure that does not require expert training or harbour undesirable side effects for the patients. Here, we review the existing literature on salivary biomarkers and examine their validity in diagnosing and monitoring neurodegenerative and neuropsychiatric disorders such as autism and Alzheimer's, Parkinson's and Huntington's disease. Based on the available research, amyloid beta peptide, tau protein, lactoferrin, alpha-synuclein, DJ-1 protein, chromogranin A, huntingtin protein, DNA methylation disruptions, and micro-RNA profiles provide display a reliable degree of consistency and validity as disease biomarkers.

Pedigree Selection and Information Content

In this article, we discuss strategies for selection of families and family members for genetic studies. We will evaluate strategies to sample large families with multiply affected members, sibships, and nuclear families. In addition, we have added a section to discuss sub-sampling within pedigrees for large sequencing studies, particularly when genome-wide SNP chips are available on all members of a pedigree. The type of family sampled for a study will determine the statistical analyses and power of discovery of genetic findings. We will evaluate study designs that maximize power and allow for linkage and association analyses to identify genetic loci predisposing to phenotype. © 2018 by John Wiley & Sons, Inc.

Dose-Dependent Lowering of Mutant Huntingtin Using Antisense Oligonucleotides in Huntington Disease Patients

On December 11 of 2017, Ionis Pharmaceuticals published a press release announcing dose-dependent reductions of mutant huntingtin protein in their HTTRx Phase 1/2a study in Huntington disease (HD) patients. The results from this Ionis trial have gained much attention from the patient community and the oligonucleotide therapeutics field, since it is the first trial targeting the cause of HD, namely the mutant huntingtin protein, using antisense oligonucleotides (ASOs). The press release also states that the primary endpoints of the study (safety and tolerability) were met, but does not contain data. This news follows the approval of another therapeutic ASO nusinersen (trade name Spinraza) for a neurological disease, spinal muscular atrophy, by the U.S. Food and Drug Administration and European Medicines Agency, in 2016 and 2017, respectively. Combined, this offers hope for the development of the HTTRx therapy for HD patients.

Reactive Neuroblastosis in Huntington's Disease: A Putative Therapeutic Target for Striatal Regeneration in the Adult Brain

The cellular and molecular mechanisms underlying the reciprocal relationship between adult neurogenesis, cognitive and motor functions have been an important focus of investigation in the establishment of effective neural replacement therapies for neurodegenerative disorders. While neuronal loss, reactive gliosis and defects in the self-repair capacity have extensively been characterized in neurodegenerative disorders, the transient excess production of neuroblasts detected in the adult striatum of animal models of Huntington’s disease (HD) and in post-mortem brain of HD patients, has only marginally been addressed. This abnormal cellular response in the striatum appears to originate from the selective proliferation and ectopic migration of neuroblasts derived from the subventricular zone (SVZ). Based on and in line with the term “reactive astrogliosis”, we propose to name the observed cellular event “reactive neuroblastosis”. Although, the functional relevance of reactive neuroblastosis is unknown, we speculate that this process may provide support for the tissue regeneration in compensating the structural and physiological functions of the striatum in lieu of aging or of the neurodegenerative process. Thus, in this review article, we comprehend different possibilities for the regulation of striatal neurogenesis, neuroblastosis and their functional relevance in the context of HD.