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BackgroundIn Huntington’s Disease (HD), cellular toxicity is particularly caused by fragments of the mutant huntingtin (HTT) protein generated by proteolytic enzymes. Lowering the levels of these toxic HTT protein fragments is hypothesized to ameliorate the consequences mutant HTT. To that end, we have developed an antisense oligonucleotide (AON) that targets HTT pre-mRNA and induces skipping of exon 12. As exon 12 contains the critical proteolytic cleavage site, the resulting HTTΔ12 protein can no longer be cleaved into its toxic fragments.AimWe aimed to determine whether skipping of exon 12 in HTT mRNA could rescue the phenotype of YAC128 mice, a model of HD that contains the full-length human HTT gene including 128 CAG-repeats.MethodsIn total 1500 µg AON was administered via three intracerebroventricular injections starting at 6 months of age. We monthly assessed motor behaviour using a rotarod and studied (hypo)activity using PhenoTyper cages (Noldus). At 12 months of age, MRI was performed to assess cerebral volume, followed by sacrifice and brain isolation for analysis of exon skip efficiency and neuropathology.ResultsAON treatment induced around 40% exon 12 skip on RNA level in the cortex of YAC128 mice. We observed a rescue of the YAC128 phenotype on body weight and activity levels by AON-mediated exon 12 skipping. However, the phenotype observed on the rotarod was not restored.ConclusionsSo far, in vivo treatment results are promising. We are currently working on confirming HTT protein modification and assessing neuropathology using immunohistochemistry, MRI data and gene expression analysis.

Huntington’s disease (HD) is a neurodegenerative genetic disorder characterized by motor, psychiatric, cognitive, and peripheral symptoms without effective therapy. Evidence suggests that lifestyle factors can modulate disease onset and progression, and environmental enrichment (EE) has emerged as a potential approach to mitigate the progression and severity of neurodegenerative processes. Wild-type (WT) and yeast artificial chromosome (YAC) 128 mice were exposed to different EE conditions. Animals from cohort 1 were exposed to EE between postnatal days 21 and 60, and animals from cohort 2 were exposed to EE between postnatal days 60 and 120. Motor and non-motor behavioral tests were employed to evaluate the effects of EE on HD progression. Monoamine levels, hippocampal cell proliferation, neuronal differentiation, and dendritic arborization were also assessed. Here we show that EE had an antidepressant-like effect and slowed the progression of motor deficits in HD mice. It also reduced monoamine levels, which correlated with better motor performance, particularly in the striatum. EE also modulated neuronal differentiation in the YAC128 hippocampus. These results confirm that EE can impact behavior, hippocampal neuroplasticity, and monoamine levels in YAC128 mice, suggesting this could be a therapeutic strategy to modulate neuroplasticity deficits in HD. However, further research is needed to fully understand EE’s mechanisms and long-term effects as an adjuvant therapy for this debilitating condition.

Environmental deprivation can have deleterious effects on adaptive myelination and oligodendroglia function. Early stage Huntington disease (HD) is characterised by white-matter myelin abnormalities in both humans and animal models. However, whether deprived environments exacerbate myelin-related pathological features of HD is not clearly understood. Here, we investigated the impact of deprivation and social isolation on ultrastructural features of myelin in the corpus callosum of the YAC128 mouse model of HD and wildtype (WT) mice using transmission electron microscopy. HD pathology on its own leads to increased representation of altered myelin features, such as thinner sheaths and compromised morphology. Interestingly, deprivation mirrors these effects in WT mice but does not greatly exacerbate the already aberrant myelin in HD mice, indicating a disease-related floor effect in the latter animals. These novel findings indicate that environmental deprivation causes abnormalities in myelin ultrastructure in the otherwise healthy corpus callosum of wild-type mice but has distinct effects on HD mice, where compromised myelin integrity is manifest from early stages of the disease.

Huntington’s disease (HD) is a fatal neurodegenerative genetic disease characterized by a loss of neurons in the striatum. It is caused by a mutation in the Huntingtin gene (HTT) that codes for the protein huntingtin (HTT). The mutant Huntingtin gene (mHTT) contains extra poly-glutamine (CAG) repeats from which the translated mutant huntingtin proteins (mHTT) undergo inappropriate post-translational modifications, conferring a toxic gain of function, in addition to its non-functional property. In order to curb the production of the mHTT, we have constructed two CRISPR (clustered regularly interspaced short palindromic repeat)-Cas9 (CRISPR associate protein) plasmids, among which one nicks the DNA at untranslated region upstream to the open reading frame (uORF), and the other nicks the DNA at exon1-intron boundary. The primary goal of this study was to apply this plasmid into mesenchymal stem cells (MSCs) extracted from the bone-marrow of YAC128 mice, which carries the transgene for HD. Our results suggest that the disruption of uORF through CRISPR-Cas9 influences the translation of mHTT negatively and, to a lesser extent, disrupts the exon1-intron boundary, which affects the translation of the mHTT. These findings also revealed the pattern of the nucleotide addition or deletion at the site of the DNA-nick in this model.

There are currently no drugs that meaningfully slow down the progression of Huntington’s disease (HD). Moreover, drug candidates against a single molecular target have not had significant success. Therefore, a different approach to HD drug discovery is needed. Previously we showed that the flavonol fisetin is efficacious in mouse and fly models of HD (Hum. Mol. Gen. 20 :261, 2011). It is also effective in animal models of Alzheimer’s disease (AD), ischemic stroke, and the CNS complications of diabetes, all of which share some pathological features with HD. Potent derivatives of fisetin with improved pharmacology were made that maintain its multiple biological activities (J. Med. Chem. 55 :378, 2012). From 160 synthetic fisetin derivatives, one, CMS121, was selected for further study in the context of HD based on pharmacological parameters and its efficacy in animal models of AD. Both R6/2 and YAC128 mouse models of HD were used in these studies. We examined motor function using multiple assays as well as survival. In the R6/2 mice, we also looked at the effects of CMS121 on striatal gene expression. In both models, we found a slowing of motor dysfunction and an increase in median life span. Interestingly, in the YAC128 mice, the effects on the slowing in motor function loss became increasingly more pronounced as the mice aged. CMS121 also reduced HD-driven changes in the expression of genes associated with the proteasome and oxidative phosphorylation. Overall, these results suggest that CMS121 could provide some benefits for HD patients, particularly with regard to increasing health span.

Huntington’s disease (HD) is a genetic neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms, accompanied by massive neuronal degeneration in the striatum. In this study, we utilized solid lipid curcumin particles (SLCPs) and solid lipid particles (SLPs) to test their efficacy in reducing deficits in YAC128 HD mice. Eleven-month-old YAC128 male and female mice were treated orally with SLCPs (100 mg/kg) or equivalent volumes of SLPs or vehicle (phosphate-buffered saline) every other day for eight weeks. Learning and memory performance was assessed using an active-avoidance task on week eight. The mice were euthanized, and their brains were processed using Golgi-Cox staining to study the morphology of medium spiny neurons (MSNs) and Western blots to quantify amounts of DARPP-32, brain-derived neurotrophic factor (BDNF), TrkB, synaptophysin, and PSD-95. We found that both SLCPs and SLPs improved learning and memory in HD mice, as measured by the active avoidance task. We also found that SLCP and SLP treatments preserved MSNs arborization and spinal density and modulated synaptic proteins. Our study shows that SLCPs, as well as the lipid particles, can have therapeutic effects in old YAC128 HD mice in terms of recovering from HD brain pathology and cognitive deficits.

Huntington's disease (HD) is a genetic neurodegenerative disorder characterized by neuronal loss and motor dysfunction. Although there is no effective treatment, stem cell transplantation offers a promising therapeutic strategy, but the safety and efficacy of this approach needs to be optimized. The purpose of this study was to test the potential of intra-striatal transplantation of induced pluripotent stem cell-derived neural stem cells (iPS-NSCs) for treating HD. For this purpose, we developed mouse adenovirus-generated iPSCs, differentiated them into neural stem cells , labeled them with Hoechst, and transplanted them bilaterally into striata of 10-month old wild type (WT) and HD YAC128 mice. We assessed the efficiency of these transplanted iPS-NSCs to reduce motor deficits in YAC128 mice by testing them on an accelerating rotarod task at 1 day prior to transplantation, and then weekly for 10 weeks. Our results showed an amelioration of locomotor deficits in YAC128 mice that received iPS-NSC transplantations. Following testing, the mice were sacrificed, and their brains were analyzed using immunohistochemistry and Western blot (WB). The results from our histological examinations revealed no signs of tumors and evidence that many iPS-NSCs survived and differentiated into region-specific neurons (medium spiny neurons) in both WT and HD mice, as confirmed by co-labeling of Hoechst-labeled transplanted cells with NeuN and DARPP-32. Also, counts of Hoechst-labeled cells revealed that a higher proportion were co-labeled with DARPP-32 and NeuN in HD-, compared to WT- mice, suggesting a dissimilar differentiation pattern in HD mice. Whereas significant decreases were found in counts of NeuN- and DARPP-32-labeled cells, and for neuronal density measures in striata of HD vehicle controls, such decrements were not observed in the iPS-NSCs-transplanted-HD mice. WB analysis showed increase of BDNF and TrkB levels in striata of transplanted HD mice compared to HD vehicle controls. Collectively, our data suggest that iPS-NSCs may provide an effective option for neuronal replacement therapy in HD.

While the genetic cause of Huntington disease (HD) is known since 1993, still no cure exists. Therapeutic development would benefit from a method to monitor disease progression and treatment efficacy, ideally using blood biomarkers. Previously, HD-specific signatures were identified in human blood representing signatures in human brain, showing biomarker potential. Since drug candidates are generally first screened in rodent models, we aimed to identify HD signatures in blood and brain of YAC128 HD mice and compare these with previously identified human signatures. RNA sequencing was performed on blood withdrawn at two time points and four brain regions from YAC128 and control mice. Weighted gene co-expression network analysis was used to identify clusters of co-expressed genes (modules) associated with the HD genotype. These HD-associated modules were annotated via text-mining to determine the biological processes they represented. Subsequently, the processes from mouse blood were compared with mouse brain, showing substantial overlap, including protein modification, cell cycle, RNA splicing, nuclear transport, and vesicle-mediated transport. Moreover, the disease-associated processes shared between mouse blood and brain were highly comparable to those previously identified in human blood and brain. In addition, we identified HD blood-specific pathology, confirming previous findings for peripheral pathology in blood. Finally, we identified hub genes for HD-associated blood modules and proposed a strategy for gene selection for development of a disease progression monitoring panel.

Huntington's disease (HD) is an autosomal dominant disease caused by an expansion of CAG repeats in the gene encoding for huntingtin. Brain metabolic dysfunction and altered Akt signaling pathways have been associated with disease progression. Nevertheless, conflicting results persist regarding the role of insulin-like growth factor-1 (IGF-1)/Akt pathway in HD. While high plasma levels of IGF-1 correlated with cognitive decline in HD patients, other data showed protective effects of IGF-1 in HD striatal neurons and R6/2 mice. Thus, in the present study, we investigated motor phenotype, peripheral and central metabolic profile, and striatal and cortical signaling pathways in YAC128 mice subjected to intranasal administration of recombinant human IGF-1 (rhIGF-1) for 2 weeks, in order to promote IGF-1 delivery to the brain. We show that IGF-1 supplementation enhances IGF-1 cortical levels and improves motor activity and both peripheral and central metabolic abnormalities in YAC128 mice. Moreover, decreased Akt activation in HD mice brain was ameliorated following IGF-1 administration. Upregulation of Akt following rhIGF-1 treatment occurred concomitantly with increased phosphorylation of mutant huntingtin on Ser421. These data suggest that intranasal administration of rhIGF-1 ameliorates HD-associated glucose metabolic brain abnormalities and mice phenotype.

Mouse models are frequently used to study Huntington’s disease (HD). The onset and severity of neuronal and behavioral pathologies vary greatly between HD mouse models, which results from different huntingtin expression levels and different CAG repeat length. HD pathology appears to depend also on the strain background of mouse models. Thus, behavioral deficits of HD mice are more severe in the FVB than in the C57BL/6 background. Alterations in medium spiny neuron (MSN) morphology and function have been well documented in young YAC128 mice in the FVB background. Here, we tested the relevance of strain background for mutant huntingtin (mHTT) toxicity on the cellular level by investigating HD pathologies in YAC128 mice in the C57BL/6 background (YAC128/BL6). Morphology, spine density, synapse function and membrane properties were not or only subtly altered in MSNs of 12-month-old YAC128/BL6 mice. Despite the mild cellular phenotype, YAC128/BL6 mice showed deficits in motor performance. More pronounced alterations in MSN function were found in the HdhQ150 mouse model in the C57BL/6 background (HdhQ150/BL6). Consistent with the differences in HD pathology, the number of inclusion bodies was considerably lower in YAC128/BL6 mice than HdhQ150/BL6 mice. This study highlights the relevance of strain background for mHTT toxicity in HD mouse models.