Silencing primary dystonia: lentiviral-mediated RNA interference therapy for DYT1 dystonia

Allele-specific genome targeting in the development of precision medicine

The CRISPR-based genome editing holds immense potential to fix disease-causing mutations, however, must also handle substantial natural genetic variations between individuals. Previous studies have shown that mismatches between the single guide RNA (sgRNA) and genomic DNA may negatively impact sgRNA efficiencies and lead to imprecise specificity prediction. Hence, the genetic variations bring about a great challenge for designing platinum sgRNAs in large human populations. However, they also provide a promising entry for designing allele-specific sgRNAs for the treatment of each individual. The CRISPR system is rather specific, with the potential ability to discriminate between similar alleles, even based on a single nucleotide difference. Genetic variants contribute to the discrimination capabilities, once they generate a novel protospacer adjacent motif (PAM) site or locate in the seed region near an available PAM. Therefore, it can be leveraged to establish allele-specific targeting in numerous dominant human disorders, by selectively ablating the deleterious alleles. So far, allele-specific CRISPR has been increasingly implemented not only in treating dominantly inherited diseases, but also in research areas such as genome imprinting, haploinsufficiency, spatiotemporal loci imaging and immunocompatible manipulations. In this review, we will describe the working principles of allele-specific genome manipulations by virtue of expanding engineering tools of CRISPR. And then we will review new advances in the versatile applications of allele-specific CRISPR targeting in treating human genetic diseases, as well as in a series of other interesting research areas. Lastly, we will discuss their potential therapeutic utilities and considerations in the era of precision medicine.

Efficient RNA interference-based knockdown of mutant torsinA reveals reversibility of PERK-eIF2α pathway dysregulation in DYT1 transgenic rats in vivo

DYT1 dystonia is a neurological disease caused by a dominant mutation that results in the loss of a glutamic acid in the endoplasmic reticulum-resident protein torsinA. Currently, treatments are symptomatic and only provide partial relief. Multiple reports support the hypothesis that selectively reducing expression of mutant torsinA without affecting levels of the wild type protein should be beneficial. Published cell-based studies support this hypothesis. It is unclear, however, if phenotypes are reversible by targeting the molecular defect once established in vivo. Here, we generated adeno-associated virus encoding artificial microRNA targeting human mutant torsinA and delivered them to the striatum of symptomatic transgenic rats that express the full human TOR1A mutant gene. We achieved efficient suppression of human mutant torsinA expression in DYT1 transgenic rats, partly reversing its accumulation in the nuclear envelope. This intervention rescued PERK-eIF2α pathway dysregulation in striatal projection neurons but not behavioral abnormalities. Moreover, we found abnormal expression of components of dopaminergic neurotransmission in DYT1 rat striatum, which were not normalized by suppressing mutant torsinA expression. Our findings demonstrate the reversibility of translational dysregulation in DYT1 neurons and confirm the presence of abnormal dopaminergic neurotransmission in DYT1 dystonia.

ASPsiRNA: A Resource of ASP-siRNAs Having Therapeutic Potential for Human Genetic Disorders and Algorithm for Prediction of Their Inhibitory Efficacy

Allele-specific siRNAs (ASP-siRNAs) have emerged as promising therapeutic molecules owing to their selectivity to inhibit the mutant allele or associated single-nucleotide polymorphisms (SNPs) sparing the expression of the wild-type counterpart. Thus, a dedicated bioinformatics platform encompassing updated ASP-siRNAs and an algorithm for the prediction of their inhibitory efficacy will be helpful in tackling currently intractable genetic disorders. In the present study, we have developed the ASPsiRNA resource (http://crdd.osdd.net/servers/aspsirna/) covering three components viz (i) ASPsiDb, (ii) ASPsiPred, and (iii) analysis tools like ASP-siOffTar. ASPsiDb is a manually curated database harboring 4543 (including 422 chemically modified) ASP-siRNAs targeting 78 unique genes involved in 51 different diseases. It furnishes comprehensive information from experimental studies on ASP-siRNAs along with multidimensional genetic and clinical information for numerous mutations. ASPsiPred is a two-layered algorithm to predict efficacy of ASP-siRNAs for fully complementary mutant (Eff^mut) and wild-type allele (Eff^wild) with one mismatch by ASPsiPred^SVM and ASPsiPred^matrix, respectively. In ASPsiPred^SVM, 922 unique ASP-siRNAs with experimentally validated quantitative Eff^mut were used. During 10-fold cross-validation (10nCV) employing various sequence features on the training/testing dataset (T737), the best predictive model achieved a maximum Pearson’s correlation coefficient (PCC) of 0.71. Further, the accuracy of the classifier to predict Eff^mut against novel genes was assessed by leave one target out cross-validation approach (LOTOCV). ASPsiPred^matrix was constructed from rule-based studies describing the effect of single siRNA:mRNA mismatches on the efficacy at 19 different locations of siRNA. Thus, ASPsiRNA encompasses the first database, prediction algorithm, and off-target analysis tool that is expected to accelerate research in the field of RNAi-based therapeutics for human genetic diseases.

Disruption of Protein Processing in the Endoplasmic Reticulum of DYT1 Knock-in Mice Implicates Novel Pathways in Dystonia Pathogenesis

Dystonia type 1 (DYT1) is a dominantly inherited neurological disease caused by mutations in TOR1A, the gene encoding the endoplasmic reticulum (ER)-resident protein torsinA. Previous work mostly completed in cell-based systems suggests that mutant torsinA alters protein processing in the secretory pathway. We hypothesized that inducing ER stress in the mammalian brain in vivo would trigger or exacerbate mutant torsinA-induced dysfunction. To test this hypothesis, we crossed DYT1 knock-in with p58(IPK)-null mice. The ER co-chaperone p58(IPK) interacts with BiP and assists in protein maturation by helping to fold ER cargo. Its deletion increases the cellular sensitivity to ER stress. We found a lower generation of DYT1 knock-in/p58 knock-out mice than expected from this cross, suggesting a developmental interaction that influences viability. However, surviving animals did not exhibit abnormal motor function. Analysis of brain tissue uncovered dysregulation of eiF2α and Akt/mTOR translational control pathways in the DYT1 brain, a finding confirmed in a second rodent model and in human brain. Finally, an unbiased proteomic analysis identified relevant changes in the neuronal protein landscape suggesting abnormal ER protein metabolism and calcium dysregulation. Functional studies confirmed the interaction between the DYT1 genotype and neuronal calcium dynamics. Overall, these findings advance our knowledge on dystonia, linking translational control pathways and calcium physiology to dystonia pathogenesis and identifying potential new pharmacological targets.

SIGNIFICANCE STATEMENT

Dystonia type 1 (DYT1) is one of the different forms of inherited dystonia, a neurological disorder characterized by involuntary, disabling movements. DYT1 is caused by mutations in the gene that encodes the endoplasmic reticulum (ER)-resident protein torsinA. How mutant torsinA causes neuronal dysfunction remains unknown. Here, we show the behavioral and molecular consequences of stressing the ER in DYT1 mice by increasing the amount of misfolded proteins. This resulted in the generation of a reduced number of animals, evidence of abnormal ER protein processing and dysregulation of translational control pathways. The work described here proposes a shared mechanism for different forms of dystonia, links for the first time known biological pathways to dystonia pathogenesis, and uncovers potential pharmacological targets for its treatment.

Tectonic 1 Is a Key Regulator of Cell Proliferation in Pancreatic Cancer

Pancreatic cancer is notoriously becoming one of the most devastating human cancers leading to death. However, clinical challenges still remain in diagnosis and treatment of this ticklish cancer. In the present study, the authors identified a new gene, Tectonic 1 (TCTN1), as a key regulator of cell proliferation in pancreatic cancer. Lentivirus-mediated short hairpin RNA (shRNA) was employed to knock down endogenous TCTN1 expression in PANC-1 pancreatic cancer cells. Knockdown of TCTN1 expression potently inhibited cell viability and proliferation, as determined by MTT and colony formation assays. Western blotting analysis also showed that knockdown of TCTN1 suppressed the expression of cdc2, while it induced that of p21 and p27. Flow cytometry analysis showed that depletion of TCTN1 in PANC-1 cells led to cell cycle arrest in the G2/M phase as well as apoptosis. Besides, depletion of TCTN1 led to the increase of Bax and cleavage of PARP-1, but the decrease of bcl2 by western blotting. The data indicate that TCTN1 is indispensable for pancreatic cancer cell proliferation, which provides a novel alternative to targeted therapy of pancreatic cancer and deserves further investigation.

Neural stem cell transplantation for the treatment of primary torsion dystonia: A case report

Primary torsion dystonia (PTD) occurs due to a genetic mutation and often advances gradually. Currently, there is no therapy available that is able to inhibit progression. Neural stem cells (NSCs) are being investigated as potential therapies for neurodegenerative diseases, such as stroke and trauma. The present study evaluated the clinical effectiveness of NSC transplantation in an 18-year-old male patient with PTD, to assess the ability of this therapy to inhibit PTD progression. Genetic testing of the patient revealed a mutation in the torsion dystonia-1 (DYT1) gene (907–909 delGAG). NSCs were bilaterally implanted in the globus pallidus of the patient through stereotactic surgery. Prior to surgery, the patient's Burke-Fahn-Marsden dystonia movement score (BFMDMS) was 21, which progressively decreased after surgery to 18, 17, 15 and 13 at 1, 2, 3 and 4 postoperative years, respectively. BFMDMS was improved by 38.1% over the 4 postoperative years. Although computed tomography and magnetic resonance imaging examinations showed no significant changes prior to and following surgery, postoperative brain positron emission tomography scans revealed increased glucose metabolism in the transplanted region. The clinical efficacy of NSC transplantation in this patient suggests its potential for the treatment of DYT1-positive patients with PTD.

Behavioral and electrophysiological characterization of Dyt1 heterozygous knockout mice

DYT1 dystonia is an inherited movement disorder caused by mutations in DYT1 (TOR1A), which codes for torsinA. Most of the patients have a trinucleotide deletion (ΔGAG) corresponding to a glutamic acid in the C-terminal region (torsinA(ΔE)). Dyt1 ΔGAG heterozygous knock-in (KI) mice, which mimic ΔGAG mutation in the endogenous gene, exhibit motor deficits and deceased frequency of spontaneous excitatory post-synaptic currents (sEPSCs) and normal theta-burst-induced long-term potentiation (LTP) in the hippocampal CA1 region. Although Dyt1 KI mice show decreased hippocampal torsinA levels, it is not clear whether the decreased torsinA level itself affects the synaptic plasticity or torsinA(ΔE) does it. To analyze the effect of partial torsinA loss on motor behaviors and synaptic transmission, Dyt1 heterozygous knock-out (KO) mice were examined as a model of a frame-shift DYT1 mutation in patients. Consistent with Dyt1 KI mice, Dyt1 heterozygous KO mice showed motor deficits in the beam-walking test. Dyt1 heterozygous KO mice showed decreased hippocampal torsinA levels lower than those in Dyt1 KI mice. Reduced sEPSCs and normal miniature excitatory post-synaptic currents (mEPSCs) were also observed in the acute hippocampal brain slices from Dyt1 heterozygous KO mice, suggesting that the partial loss of torsinA function in Dyt1 KI mice causes action potential-dependent neurotransmitter release deficits. On the other hand, Dyt1 heterozygous KO mice showed enhanced hippocampal LTP, normal input-output relations and paired pulse ratios in the extracellular field recordings. The results suggest that maintaining an appropriate torsinA level is important to sustain normal motor performance, synaptic transmission and plasticity. Developing therapeutics to restore a normal torsinA level may help to prevent and treat the symptoms in DYT1 dystonia.

Lentivirus-Mediated Knockdown of TCTN1 Inhibits Glioma Cell Proliferation

Tectonic-1, also named as TCTN1 or TECT1, which belongs to a family of signal-sequence-containing secreted and transmembrane proteins evolutionarily conserved among eukaryotes, was reported to be involved in central nervous system development and ciliogenesis. In this paper, we found that TCTN1 is extensively expressed in human glioma cell lines. To clarify the role of TCTN1 in glioma, we employed lentivirus-mediated short hairpin RNA to knock down TCTN1 expression in U251 and U87MG glioma cells. Knockdown of TCTN1 potently inhibited cell proliferation, as determined by MTT and colony formation assays. Cell cycle analysis showed depletion of TCTN1 led to both U251 and U87MG cells arrested in the G0/G1 phase. These data suggest TCTN1 is essential for glioma cell viability, and dysregulation of TCTN1 may play a key role in glioma tumorigenesis.

Current Gaps in the Understanding of the Subcellular Distribution of Exogenous and Endogenous Protein TorsinA

Background

An in-frame deletion leading to the loss of a single glutamic acid residue in the protein torsinA (ΔE-torsinA) results in an inherited movement disorder, DYT1 dystonia. This autosomal dominant disease affects the function of the brain without causing neurodegeneration, by a mechanism that remains unknown.

Methods

We evaluated the literature regarding the subcellular localization of torsinA.

Results

Efforts to elucidate the pathophysiological basis of DYT1 dystonia have relied partly on examining the subcellular distribution of the wild-type and mutated proteins. A typical approach is to introduce the human torsinA gene (TOR1A) into host cells and overexpress the protein therein. In both neurons and non-neuronal cells, exogenous wild-type torsinA introduced in this manner has been found to localize mainly to the endoplasmic reticulum, whereas exogenous ΔE-torsinA is predominantly in the nuclear envelope or cytoplasmic inclusions. Although these outcomes are relatively consistent, findings for the localization of endogenous torsinA have been variable, leaving its physiological distribution a matter of debate.

Discussion

As patients’ cells do not overexpress torsinA proteins, it is important to understand why the reported distributions of the endogenous proteins are inconsistent. We propose that careful optimization of experimental methods will be critical in addressing the causes of the differences among the distributions of endogenous (non-overexpressed) vs. exogenously introduced (overexpressed) proteins.

TorsinA hypofunction causes abnormal twisting movements and sensorimotor circuit neurodegeneration

Lack of a preclinical model of primary dystonia that exhibits dystonic-like twisting movements has stymied identification of the cellular and molecular underpinnings of the disease. The classical familial form of primary dystonia is caused by the DYT1 (ΔE) mutation in TOR1A, which encodes torsinA, AAA⁺ ATPase resident in the lumen of the endoplasmic reticular/nuclear envelope. Here, we found that conditional deletion of Tor1a in the CNS (nestin-Cre Tor1a(flox/-)) or isolated CNS expression of DYT1 mutant torsinA (nestin-Cre Tor1a(flox/ΔE)) causes striking abnormal twisting movements. These animals developed perinuclear accumulation of ubiquitin and the E3 ubiquitin ligase HRD1 in discrete sensorimotor regions, followed by neurodegeneration that was substantially milder in nestin-Cre Tor1a(flox/ΔE) compared with nestin-Cre Tor1a(flox/-) animals. Similar to the neurodevelopmental onset of DYT1 dystonia in humans, the behavioral and histopathological abnormalities emerged and became fixed during CNS maturation in the murine models. Our results establish a genetic model of primary dystonia that is overtly symptomatic, and link torsinA hypofunction to neurodegeneration and abnormal twisting movements. These findings provide a cellular and molecular framework for how impaired torsinA function selectively disrupts neural circuits and raise the possibility that discrete foci of neurodegeneration may contribute to the pathogenesis of DYT1 dystonia.

Nuclear envelope breakdown induced by herpes simplex virus type 1 involves the activity of viral fusion proteins

Herpesvirus infection reorganizes components of the nuclear lamina usually without loss of integrity of the nuclear membranes. We report that wild-type HSV infection can cause dissolution of the nuclear envelope in transformed mouse embryonic fibroblasts that do not express torsinA. Nuclear envelope breakdown is accompanied by an eight-fold inhibition of virus replication. Breakdown of the membrane is much more limited during infection with viruses that lack the gB and gH genes, suggesting that breakdown involves factors that promote fusion at the nuclear membrane. Nuclear envelope breakdown is also inhibited during infection with virus that does not express UL34, but is enhanced when the US3 gene is deleted, suggesting that envelope breakdown may be enhanced by nuclear lamina disruption. Nuclear envelope breakdown cannot compensate for deletion of the UL34 gene suggesting that mixing of nuclear and cytoplasmic contents is insufficient to bypass loss of the normal nuclear egress pathway.

Inhibiting metastatic breast cancer cell migration via the synergy of targeted, pH-triggered siRNA delivery and chemokine axis blockade

Because breast cancer patient survival inversely correlates with metastasis, we engineered vehicles to inhibit both the C-X-C chemokine receptor type 4 (CXCR4) and lipocalin-2 (Lcn2) mediated migratory pathways. pH-responsive liposomes were designed to protect and trigger the release of Lcn2 siRNA. Liposomes were modified with anti-CXCR4 antibodies to target metastatic breast cancer (MBC) cells and block migration along the CXCR4-CXCL12 axis. This synergistic approach--coupling the CXCR4 axis blockade with Lcn2 silencing--significantly reduced migration in triple-negative human breast cancer cells (88% for MDA-MB-436 and 92% for MDA-MB-231). The results suggested that drug delivery vehicles engineered to attack multiple migratory pathways may effectively slow progression of MBC.

Dystonia as a network disorder: what is the role of the cerebellum?

The dystonias are a group of disorders defined by sustained or intermittent muscle contractions that result in involuntary posturing or repetitive movements. There are many different clinical manifestations and causes. Although they traditionally have been ascribed to dysfunction of the basal ganglia, recent evidence has suggested dysfunction may originate from other regions, particularly the cerebellum. This recent evidence has led to an emerging view that dystonia is a network disorder that involves multiple brain regions. The new network model for the pathogenesis of dystonia has raised many questions, particularly regarding the role of the cerebellum. For example, if dystonia may arise from cerebellar dysfunction, then why are there no cerebellar signs in dystonia? Why are focal cerebellar lesions or degenerative cerebellar disorders more commonly associated with ataxia rather than dystonia? Why is dystonia more commonly associated with basal ganglia lesions rather than cerebellar lesions? Can answers obtained from animals be extrapolated to humans? Is there any evidence that the cerebellum is not involved? Finally, what is the practical value of this new model of pathogenesis for the neuroscientist and clinician? This article explores potential answers to these questions.

Lentiviral vector-mediated RNA silencing in the central nervous system

RNA silencing is an established method for investigating gene function and has attracted particular interest because of the potential for generating RNA-based therapeutics. Using lentiviral vectors as an efficient delivery system that offers stable, long-term expression in postmitotic cells further enhances the applicability of an RNA-based gene therapy for the CNS. In this review we provide an overview of both lentiviral vectors and RNA silencing along with design considerations for generating lentiviral vectors capable of RNA silencing. We go on to describe the current preclinical data regarding lentiviral vector-mediated RNA silencing for CNS disorders and discuss the concerns of side effects associated with lentiviral vectors and small interfering RNAs and how these might be mitigated.

A novel mutation in PLP1 causes severe hereditary spastic paraplegia type 2

Hereditary spastic paraplegia (HSP) type 2 is a proteolipid protein (PLP1)-related genetic disorder that is characterized by dysmyelination of the central nervous system resulting primarily in limb spasticity, cognitive impairment, nystagmus, and spastic urinary bladder of varying severity. Previously reported PLP1 mutations include duplications, point mutations, or whole gene deletions with a continuum of phenotypes ranging from severe Pelizaeus-Merzbacher disease (PMD) to uncomplicated HSP type 2. In this manuscript we report a novel PLP1 missense mutation (c.88G>C) in a family from Argentina. This mutation is in a highly conserved transmembrane domain of PLP1 and the mutant protein was found to be retained in the endoplasmic reticulum when expressed in vitro. Due to the variable expressivity that characterizes these disorders our report contributes to the knowledge of genotype-phenotype correlations of PLP1-related disorders.

Recent advances in RNA interference therapeutics for CNS diseases

Over the last decade, RNA interference technology has shown therapeutic promise in rodent models of dominantly inherited brain diseases, including those caused by polyglutamine repeat expansions in the coding region of the affected gene. For some of these diseases, proof-of concept studies in model organisms have transitioned to safety testing in larger animal models, such as the nonhuman primate. Here, we review recent progress on RNA interference-based therapies in various model systems. We also highlight outstanding questions or concerns that have emerged as a result of an improved (and ever advancing) understanding of the technologies employed.

The focal dystonias: current views and challenges for future research

The most common forms of dystonia are those that develop in adults and affect a relatively isolated region of the body. Although these adult-onset focal dystonias are most prevalent, knowledge of their etiologies and pathogenesis has lagged behind some of the rarer generalized dystonias, in which the identification of genetic defects has facilitated both basic and clinical research. This summary provides a brief review of the clinical manifestations of the adult-onset focal dystonias, focusing attention on less well understood clinical manifestations that need further study. It also provides a simple conceptual model for the similarities and differences among the different adult-onset focal dystonias as a rationale for lumping them together as a class of disorders while at the same time splitting them into subtypes. The concluding section outlines some of the most important research questions for the future. Answers to these questions are critical for advancing our understanding of this group of disorders and for developing novel therapeutics.

RNAi or overexpression: alternative therapies for Spinocerebellar Ataxia Type 1

Spinocerebellar Ataxia Type 1 (SCA1) is an autosomal dominant late onset neurodegenerative disease caused by an expanded polyglutamine tract in ataxin-1. Here, we compared the protective effects of overexpressing ataxin-1-like using recombinant AAVs, or reducing expression of mutant ataxin-1 using virally delivered RNA interference (RNAi), in a transgenic mouse model of SCA1. For the latter, we used an artificial microRNA (miR) design that optimizes potency, efficacy and safety to suppress ataxin-1 expression (miS1). Delivery of either ataxin-1-like or miS1 viral vectors to SCA1 mice cerebella resulted in widespread cerebellar Purkinje cell transduction and improved behavioral and histological phenotypes. Our data indicate the utility of either approach as a possible therapy for SCA1 patients.

Animal models for drug discovery in dystonia

Dystonia is a neurological disorder characterized by involuntary twisting movements and unnatural postures. There are many different forms of dystonia, which affect over three million people worldwide. Effective treatments are available only for a minority of patients, so new treatments are sorely needed. Several animal species have been used to develop models for different forms of dystonia, each with differing strengths and weaknesses. This review outlines the strategies that have been used to exploit these models for drug discovery. Some have been used to dissect the pathogenesis of dystonia for the identification of molecular targets for intervention. Others have been used for the empirical identification of candidate drugs. Therefore, the animal models provide promising new tools for developing better treatments for dystonia.

RNAi-based nanomedicines for targeted personalized therapy

RNA interference (RNAi) has just made it through the pipeline to clinical trials. However, in order for RNAi to serve as an ideal personalized therapeutics and be clinically approved-safe, specific, and potent strategies must be devised for efficient delivery of RNAi payloads to specific cell types, which despite the immense potential, remains a challenge. Through evaluating the recent reported studies in this field, we introduce the progress in designing targeted nano-scaled strategies that are anticipated to overcome the delivery drawbacks and along with the exciting "omics" discipline to personalize RNAi-based therapeutics.

Lentiviral vector-mediated RNA interference targeted against prohibitin inhibits apoptosis of the retinoic acid-resistant acute promyelocytic leukemia cell line NB4-R1

To investigate the possibility of prohibitin (PHB) inhibition by lentiviral vector-mediated RNA interference (RNAi) and its influence on cell apoptosis in the retinoic acid-resistant acute promyelocytic leukemia cell line NB4-R1, a lentiviral vector encoding a short hairpin RNA (shRNA) targeted against PHB (pGCSIL-GFP-PHB) was constructed and transfected into the packaging cells 293T, and the viral supernatant was collected to transfect NB4-R1 cells. Quantitative real-time fluorescent PCR and western blotting were used to detect the expression levels of PHB. Flow cytometry and detection of enzymatic activity of caspase-3 by western blotting were employed to examine cell apoptosis. Our results provide evidence that the lentiviral vector pGCSIL-GFP-PHB was constructed successfully, and the PHB mRNA and the protein expression inhibitory rates were 90.3 and 95.8%, respectively. When compared to the control group, the activity of caspase-3 decreased significantly, which showed a 57.3% downregulation, and the apoptosis rate was reduced by 44.6% (P<0.05). In conclusion, downregulation of the PHB gene may inhibit apoptosis of NB4-R1 cells, and it is speculated that this was at least partly due to the downregulation of caspase-3, and PHB may be a novel target for gene therapy for retinoic acid-resistant acute promyelocytic leukemia.

The ubiquitin ligase F-box/G-domain protein 1 promotes the degradation of the disease-linked protein torsinA through the ubiquitin-proteasome pathway and macroautophagy

DYT1 dystonia is a dominantly inherited, disabling neurological disorder with low penetrance that is caused by the deletion of a glutamic acid (ΔE) in the protein torsinA. We previously showed that torsinA(wt) is degraded through macroautophagy while torsinA(ΔE) is targeted to the ubiquitin-proteasome pathway (UPP). The different catabolism of torsinA(wt) and (ΔE) potentially modulates torsinA(wt):torsinA(ΔE) stoichiometry. Therefore, gaining a mechanistic understanding on how the protein quality control machinery clears torsinA(ΔE) in neurons may uncover important regulatory steps in disease pathogenesis. Here, we asked whether F-box/G-domain protein 1 (FBG1), a ubiquitin ligase known to degrade neuronal glycoproteins, is implicated in the degradation of torsinA(ΔE) by the UPP. In a first set of studies completed in cultured cells, we show that FBG1 interacts with and influences the steady-state levels of torsinA(wt) and (ΔE). Interestingly, FBG1 achieves this effect promoting the degradation of torsinA not only through the UPP, but also by macroautophagy. To determine the potential clinical significance of these findings, we asked if eliminating expression of Fbg1 triggers a motor phenotype in torsinA(ΔE) knock in (KI) mice, a model of non-manifesting DYT1 mutation carriers. We detected differences in spontaneous locomotion between aged torsinA(ΔE) KI-Fbg1 knock out and control mice. Furthermore, neuronal levels of torsinA were unaltered in Fbg1 null mice, indicating that redundant systems likely compensate in vivo for the absence of this ubiquitin ligase. In summary, our studies support a non-essential role for FBG1 on the degradation of torsinA and uncover a novel link of FBG1 to the autophagy pathway.

Illuminating the gateway of gene silencing: perspective of RNA interference technology in clinical therapeutics

A novel laboratory revolution for disease therapy, the RNA interference (RNAi) technology, has adopted a new era of molecular research as the next generation "Gene-targeted prophylaxis." In this review, we have focused on the chief technological challenges associated with the efforts to develop RNAi-based therapeutics that may guide the biomedical researchers. Many non-curable maladies, like neurodegenerative diseases and cancers have effectively been cured using this technology. Rapid advances are still in progress for the development of RNAi-based technologies that will be having a major impact on medical research. We have highlighted the recent discoveries associated with the phenomenon of RNAi, expression of silencing molecules in mammals along with the vector systems used for disease therapeutics.

Functional analysis of dopaminergic systems in a DYT1 knock-in mouse model of dystonia

The dystonias are a group of disorders characterized by involuntary twisting movements and abnormal posturing. The most common of the inherited dystonias is DYT1 dystonia, which is due to deletion of a single GAG codon (ΔE) in the TOR1A gene that encodes torsinA. Since some forms of dystonia have been linked with dysfunction of brain dopamine pathways, the integrity of these pathways was explored in a knock-in mouse model of DYT1 dystonia. In DYT1(ΔE) knock-in mice, neurochemical measures revealed only small changes in the content of dopamine or its metabolites in tissue homogenates from caudoputamen or midbrain, but microdialysis studies revealed robust decreases in baseline and amphetamine-stimulated extracellular dopamine in the caudoputamen. Quantitative stereological methods revealed no evidence for striatal or midbrain atrophy, but substantia nigra neurons immunopositive for tyrosine hydroxylase were slightly reduced in numbers and enlarged in size. Behavioral studies revealed subtle abnormalities in gross motor activity and motor coordination without overt dystonia. Neuropharmacological challenges of dopamine systems revealed normal behavioral responses to amphetamine and a minor increase in sensitivity to haloperidol. These results demonstrate that this DYT1(ΔE) knock-in mouse model of dystonia harbors neurochemical and structural changes of the dopamine pathways, as well as motor abnormalities.

Construction of permanently inducible miRNA-based expression vectors using site-specific recombinases

Background

RNA interference (RNAi) is a conserved gene silencing mechanism mediated by small inhibitory microRNAs (miRNAs).

Promoter-driven miRNA expression vectors have emerged as important tools for delivering natural or artificially designed miRNAs to eukaryotic cells and organisms. Such systems can be used to query the normal or pathogenic functions of natural miRNAs or messenger RNAs, or to therapeutically silence disease genes.

Results

As with any molecular cloning procedure, building miRNA-based expression constructs requires a time investment and some molecular biology skills. To improve efficiency and accelerate the construction process, we developed a method to rapidly generate miRNA expression vectors using recombinases instead of more traditional cut-and-paste molecular cloning techniques. In addition to streamlining the construction process, our cloning strategy provides vectors with added versatility. In our system, miRNAs can be constitutively expressed from the U6 promoter, or inducibly expressed by Cre recombinase. We also engineered a built-in mechanism to destroy the vector with Flp recombinase, if desired. Finally, to further simplify the construction process, we developed a software package that automates the prediction and design of optimal miRNA sequences using our system.

Conclusions

We designed and tested a modular system to rapidly clone miRNA expression cassettes. Our strategy reduces the hands-on time required to successfully generate effective constructs, and can be implemented in labs with minimal molecular cloning expertise. This versatile system provides options that permit constitutive or inducible miRNA expression, depending upon the needs of the end user. As such, it has utility for basic or translational applications.

Current prospects for RNA interference-based therapies

RNA interference (RNAi) is a powerful approach for reducing expression of endogenously expressed proteins. It is widely used for biological applications and is being harnessed to silence mRNAs encoding pathogenic proteins for therapy. Various methods - including delivering RNA oligonucleotides and expressing RNAi triggers from viral vectors - have been developed for successful RNAi in cell culture and in vivo. Recently, RNAi-based gene silencing approaches have been demonstrated in humans, and ongoing clinical trials hold promise for treating fatal disorders or providing alternatives to traditional small molecule therapies. Here we describe the broad range of approaches to achieve targeted gene silencing for therapy, discuss important considerations when developing RNAi triggers for use in humans, and review the current status of clinical trials.

Mechanism of neuroprotective mitochondrial remodeling by PKA/AKAP1

The mitochondrial signaling complex PKA/AKAP1 protects neurons against mitochondrial fragmentation and cell death by phosphorylating and inactivating the mitochondrial fission enzyme Drp1.

Mitochondrial shape is determined by fission and fusion reactions catalyzed by large GTPases of the dynamin family, mutation of which can cause neurological dysfunction. While fission-inducing protein phosphatases have been identified, the identity of opposing kinase signaling complexes has remained elusive. We report here that in both neurons and non-neuronal cells, cAMP elevation and expression of an outer-mitochondrial membrane (OMM) targeted form of the protein kinase A (PKA) catalytic subunit reshapes mitochondria into an interconnected network. Conversely, OMM-targeting of the PKA inhibitor PKI promotes mitochondrial fragmentation upstream of neuronal death. RNAi and overexpression approaches identify mitochondria-localized A kinase anchoring protein 1 (AKAP1) as a neuroprotective and mitochondria-stabilizing factor in vitro and in vivo. According to epistasis studies with phosphorylation site-mutant dynamin-related protein 1 (Drp1), inhibition of the mitochondrial fission enzyme through a conserved PKA site is the principal mechanism by which cAMP and PKA/AKAP1 promote both mitochondrial elongation and neuronal survival. Phenocopied by a mutation that slows GTP hydrolysis, Drp1 phosphorylation inhibits the disassembly step of its catalytic cycle, accumulating large, slowly recycling Drp1 oligomers at the OMM. Unopposed fusion then promotes formation of a mitochondrial reticulum, which protects neurons from diverse insults.

Mitochondria, the cellular powerhouse, are highly dynamic organelles shaped by opposing fission and fusion events. Research over the past decade has identified many components of the mitochondrial fission/fusion machinery and led to the discovery that mutations in genes coding for these proteins can cause human neurological diseases. While it is well established that mitochondrial shape changes are intimately involved in cellular responses to environmental stressors, we know very little about the mechanisms by which cells dynamically adjust mitochondrial form and function. In this report, we show that the scaffold protein AKAP1 brings the cAMP-dependent protein kinase PKA to the outer mitochondrial membrane to protect neurons from injury. The PKA/AKAP1 complex functions by inhibiting Drp1, an enzyme that mechanically constricts and eventually severs mitochondria. Whereas active, dephosphorylated Drp1 rapidly cycles between cytosol and mitochondria, phosphorylated Drp1 builds up in inactive mitochondrial complexes, allowing mitochondria to fuse into a neuroprotective reticulum. Our results suggest that altering the balance of kinase and phosphatase activities at the outer mitochondrial membrane may provide the basis for novel neuroprotective therapies.

Lethal toxicity caused by expression of shRNA in the mouse striatum: implications for therapeutic design

Therapeutic RNA interference has emerged as a promising approach for the treatment of many incurable diseases, including cancer, infectious disease or neurodegenerative disorders. Demonstration of efficacy and safety in animal models is necessary before planning human application. Our group and others have previously shown the potential of this approach for the dominantly-inherited neurological disease DYT1 dystonia by achieving potent shRNA-mediated silencing of the disease protein, torsinA, in cultured cells. To establish the feasibility of this approach in vivo, we pursued viral delivery of shRNA in two different mouse models. Surprisingly, intrastriatal injections of AAV2/1 vectors expressing different shRNAs, whether targeting torsinA expression or mismatched controls, resulted in significant toxicity with progressive weight loss, motor dysfunction and animal demise. Histological analysis showed shRNA-induced neurodegeneration. Toxicity was not observed in animals that received control AAV2/1 encoding no shRNA, and was independent of genotype, occurring in both DYT1 and wild type animals. Interestingly, the different genetic background of both mouse models influenced toxicity, being earlier and more severe in 129/SvEv than C57BL/6 mice. In conclusion, our studies demonstrate that expression of shRNA in the mammalian brain can lead to lethal toxicity. Furthermore, the genetic background of rodents modifies their sensitivity to this form of toxicity, a factor that should be taken into consideration in the design of preclinical therapeutic RNAi trials.

Exploring the influence of torsinA expression on protein quality control

DYT1 dystonia is caused by a glutamic acid deletion (ΔE) in the endoplasmic reticulum (ER) protein torsinA. Previous studies suggest that torsinA modulates the aggregation of cytosolic misfolded proteins and ER stress responses, although the mechanisms underlying those effects remain unclear. In order to investigate the bases of these observations, we analyzed the interaction between torsinA expression, protein aggregation and ER stress in PC6.3 cells. Unexpectedly, we found that expression of torsinA(wt) or (ΔE) does not influence the inclusion formation by an expanded polyglutamine reporter protein in this cellular model. Furthermore, torsinA does not prevent the activation of ER stress induced by thapsigargin or the reducing agent DTT. Interestingly, DTT induces post-translational changes in torsinA, more prominently for torsinA(wt) than (ΔE). This work highlights the importance of model system selection for the study of torsinA function. Furthermore, it provides additional evidence suggesting that torsinA is sensitive to changes in the cellular redox potential.

The dominant-negative von Willebrand factor gene deletion p.P1127_C1948delinsR: molecular mechanism and modulation

Understanding molecular mechanisms in the dominant inheritance of von Willebrand disease would improve our knowledge of pathophysiologic processes underlying its prevalence. Cellular models of severe type 2 von Willebrand disease, caused by a heterozygous deletion in the von Willebrand factor (VWF) gene, were produced to investigate the altered biosynthesis. Coexpression of the wild-type and in-frame deleted (p.P1127_C1948delinsR) VWF forms impaired protein secretion, high molecular weight multimer formation and function (VWF collagen-binding 1.9% ± 0.5% of wild-type), which mimicked the patient's phenotype. mRNA, protein, and cellular studies delineated the highly efficient dominant-negative mechanism, based on the key role of heterodimers as multimer terminators. The altered VWF, synthesized in large amounts with the correctly encoded "cysteine knot" domain, formed heterodimers and heterotetramers with wild-type VWF, in addition to deleted homodimers. Impaired multimerization was associated with reduced amounts of VWF in late endosomes. Correction of the dominant-negative effect was explored by siRNAs targeting the mRNA breakpoint, which selectively inhibited the in-frame deleted VWF expression. Although the small amount of the deleted protein synthesized after inhibition still exerted dominant, even though weakened, negative effects, the siRNA treatment restored secretion of large multimers with improved function (VWF collagen-binding 28.0% ± 3.3% of wild-type).

RNAi reduces expression and intracellular retention of mutant cartilage oligomeric matrix protein

Mutations in cartilage oligomeric matrix protein (COMP), a large extracellular glycoprotein expressed in musculoskeletal tissues, cause two skeletal dysplasias, pseudoachondroplasia and multiple epiphyseal dysplasia. These mutations lead to massive intracellular retention of COMP, chondrocyte death and loss of growth plate chondrocytes that are necessary for linear growth. In contrast, COMP null mice have only minor growth plate abnormalities, normal growth and longevity. This suggests that reducing mutant and wild-type COMP expression in chondrocytes may prevent the toxic cellular phenotype causing the skeletal dysplasias. We tested this hypothesis using RNA interference to reduce steady state levels of COMP mRNA. A panel of shRNAs directed against COMP was tested. One shRNA (3B) reduced endogenous and recombinant COMP mRNA dramatically, regardless of expression levels. The activity of the shRNA against COMP mRNA was maintained for up to 10 weeks. We also demonstrate that this treatment reduced ER stress. Moreover, we show that reducing steady state levels of COMP mRNA alleviates intracellular retention of other extracellular matrix proteins associated with the pseudoachondroplasia cellular pathology. These findings are a proof of principle and the foundation for the development of a therapeutic intervention based on reduction of COMP expression.

Chemical enhancement of torsinA function in cell and animal models of torsion dystonia

Movement disorders represent a significant societal burden for which therapeutic options are limited and focused on treating disease symptomality. Early-onset torsion dystonia (EOTD) is one such disorder characterized by sustained and involuntary muscle contractions that frequently cause repetitive movements or abnormal postures. Transmitted in an autosomal dominant manner with reduced penetrance, EOTD is caused in most cases by the deletion of a glutamic acid (DeltaE) in the DYT1 (also known as TOR1A) gene product, torsinA. Although some patients respond well to anticholingerics, therapy is primarily limited to either neurosurgery or chemodenervation. As mutant torsinA (DeltaE) expression results in decreased torsinA function, therapeutic strategies directed toward enhancement of wild-type (WT) torsinA activity in patients who are heterozygous for mutant DYT1 may restore normal cellular functionality. Here, we report results from the first-ever screen for candidate small molecule therapeutics for EOTD, using multiple activity-based readouts for torsinA function in Caenorhabditis elegans, subsequent validation in human DYT1 patient fibroblasts, and behavioral rescue in a mouse model of DYT1 dystonia. We exploited the nematode to rapidly discern chemical effectors of torsinA and identified two classes of antibiotics, quinolones and aminopenicillins, which enhance WT torsinA activity in two separate in vivo assays. Representative molecules were assayed in EOTD patient fibroblasts for improvements in torsinA-dependent secretory function, which was improved significantly by ampicillin. Furthermore, a behavioral defect associated with an EOTD mouse knock-in model was also rescued following administration of ampicillin. These combined data indicate that specific small molecules that enhance torsinA activity represent a promising new approach toward therapeutic development for EOTD, and potentially for other diseases involving the processing of mutant proteins.

Increased sensorimotor network activity in DYT1 dystonia: a functional imaging study

Neurophysiological studies have provided evidence of primary motor cortex hyperexcitability in primary dystonia, but several functional imaging studies suggest otherwise. To address this issue, we measured sensorimotor activation at both the regional and network levels in carriers of the DYT1 dystonia mutation and in control subjects. We used (15)Oxygen-labelled water and positron emission tomography to scan nine manifesting DYT1 carriers, 10 non-manifesting DYT1 carriers and 12 age-matched controls while they performed a kinematically controlled motor task; they were also scanned in a non-motor audio-visual control condition. Within- and between-group contrasts were analysed with statistical parametric mapping. For network analysis, we first identified a normal motor-related activation pattern in a set of 39 motor and audio-visual scans acquired in an independent cohort of 18 healthy volunteer subjects. The expression of this pattern was prospectively quantified in the motor and control scans acquired in each of the gene carriers and controls. Network values for the three groups were compared with ANOVA and post hoc contrasts. Voxel-wise comparison of DYT1 carriers and controls revealed abnormally increased motor activation responses in the former group (P < 0.05, corrected; statistical parametric mapping), localized to the sensorimotor cortex, dorsal premotor cortex, supplementary motor area and the inferior parietal cortex. Network analysis of the normative derivation cohort revealed a significant normal motor-related activation pattern topography (P < 0.0001) characterized by covarying neural activity in the sensorimotor cortex, dorsal premotor cortex, supplementary motor area and cerebellum. In the study cohort, normal motor-related activation pattern expression measured during movement was abnormally elevated in the manifesting gene carriers (P < 0.001) but not in their non-manifesting counterparts. In contrast, in the non-motor control condition, abnormal increases in network activity were present in both groups of gene carriers (P < 0.001). In this condition, normal motor-related activation pattern expression in non-manifesting carriers was greater than in controls, but lower than in affected carriers. In the latter group, measures of normal motor-related activation pattern expression in the audio-visual condition correlated with independent dystonia clinical ratings (r = 0.70, P = 0.04). These findings confirm that overexcitability of the sensorimotor system is a robust feature of dystonia. The presence of elevated normal motor-related activation pattern expression in the non-motor condition suggests that abnormal integration of audio-visual input with sensorimotor network activity is an important trait feature of this disorder. Lastly, quantification of normal motor-related activation pattern expression in individual cases may have utility as an objective descriptor of therapeutic response in trials of new treatments for dystonia and related disorders.

Lentiviral vector-mediated gene transfer and RNA silencing technology in neuronal dysfunctions

Lentiviral-mediated gene transfer in vivo or in cultured mammalian neurons can be used to address a wide variety of biological questions, to design animal models for specific neurodegenerative pathologies, or to test potential therapeutic approaches in a variety of brain disorders. Lentiviruses can infect nondividing cells, thereby allowing stable gene transfer in postmitotic cells such as mature neurons. An important contribution has been the use of inducible vectors: the same animal can thus be used repeatedly in the doxycycline-on or -off state, providing a powerful mean for assessing the function of a gene candidate in a disorder within a specific neuronal circuit. Furthermore, lentivirus vectors provide a unique tool to integrate siRNA expression constructs with the aim to locally knockdown expression of a specific gene, enabling to assess the function of a gene in a very specific neuronal pathway. Lentiviral vector-mediated delivery of short hairpin RNA results in persistent knockdown of gene expression in the brain. Therefore, the use of lentiviruses for stable expression of siRNA in brain is a powerful aid to probe gene functions in vivo and for gene therapy of diseases of the central nervous system. In this chapter, I review the applications of lentivirus-mediated gene transfer in the investigation of specific gene candidates involved in major brain disorders and neurodegenerative processes. Major applications have been in polyglutamine disorders, such as synucleinopathies and Parkinson's disease, or in investigating gene function in Huntington's disease, dystonia, or muscular dystrophy. Recently, lentivirus gene transfer has been an invaluable tool for evaluation of gene function in behavioral disorders such as drug addiction and attention-deficit hyperactivity disorder or in learning and cognition.

The therapeutic potential of microRNAs in nervous system damage, degeneration, and repair

MicroRNAS (miRNAs) have been suggested to play important roles in the central nervous system during development as well as disease. miRNAs appear to be dysregulated in a number of neurodegenerative diseases, developmental disorders, and as a result of stroke. Each miRNA has the ability to regulate hundreds of messenger RNA transcripts, both by causing degradation of the mRNA and by inhibition of protein translation. Recent findings suggest that it may eventually be possible to treat some neurological disorders by restoring or inhibiting miRNAs altered by disease pathology. Both viral delivery and administration of modified oligonucleotides mimicking or inhibiting specific miRNAs have been effective in model systems. Artificial miRNAs have also been generated for the repression of specific transcripts. Alteration of miRNA expression by disease and insult also holds the potential for improved diagnostic tools. Finally, miRNAs have been shown to control cellular proliferation and specification, suggesting that manipulation of miRNAs in cultured cells could result in more convenient generation of pure cell populations for transplantation.

Tf-lipoplex-mediated c-Jun silencing improves neuronal survival following excitotoxic damage in vivo

Excitotoxicity is one of the main features responsible for neuronal cell death after acute brain injury and in several neurodegenerative disorders, for which only few therapeutic options are currently available. In this work, RNA interference was employed to identify and validate a potential target for successful treatment of excitotoxic brain injury, the transcription factor c-Jun. The nuclear translocation of c-Jun and its upregulation are early events following glutamate-induced excitotoxic damage in primary neuronal cultures. We present evidence for the efficient knockdown of this transcription factor using a non-viral vector consisting of cationic liposomes associated to transferrin (Tf-lipoplexes). Tf-lipoplexes were able to deliver anti-c-Jun siRNAs to neuronal cells in culture, resulting in efficient silencing of c-Jun mRNA and protein and in a significant decrease of cell death following glutamate-induced damage or oxygen-glucose deprivation. This formulation also leads to a significant c-Jun knockdown in the mouse hippocampus in vivo, resulting in the attenuation of both neuronal death and inflammation following kainic acid-mediated lesion of this region. Furthermore, a strong reduction of seizure activity and cytokine production was observed in animals treated with anti-c-Jun siRNAs. These findings demonstrate the efficient delivery of therapeutic siRNAs to the brain by Tf-lipoplexes and validate c-Jun as a promising therapeutic target in neurodegenerative disorders involving excitotoxic lesions.

Transcriptional and proteomic profiling in a cellular model of DYT1 dystonia

DYT1, the most common inherited dystonia, is caused by a common dominant mutation in the TOR1A gene that leads to a glutamic acid deletion in the protein torsinA. Wild-type torsinA locates preferentially in the endoplasmic reticulum while the disease-linked mutant accumulates in the nuclear envelope. As a result, it has been proposed that DYT1 pathogenesis could result either from transcriptional dysregulation caused by abnormal interactions of mutant torsinA with nuclear envelope proteins, or from a loss of torsinA function in the endoplasmic reticulum that would impair specific neurobiological pathways. Aiming to determine whether one or both of these potential mechanisms are implicated in DYT1 pathogenesis, we completed unbiased transcriptional and proteomic profiling in well-characterized neural cell lines that inducibly express wild-type or mutant torsinA. These experiments demonstrated that the accumulation of mutant torsinA in the nuclear envelope is not sufficient to cause transcriptional dysregulation. However, we detected expression changes at the protein level that, together with other reports, suggest a potential implication of torsinA on energy metabolism and regulation of the redox state. Furthermore, several proteins identified in this study have been previously linked to other forms of dystonia. In conclusion, our results argue against the hypothesis of transcriptional dysregulation in DYT1 dystonia, suggesting potential alternative pathogenic pathways.

Therapy for prion diseases: Insights from the use of RNA interference

Insights into the molecular basis and the temporal evolution of neurotoxicity in prion disease are increasing, and recent work in mice leads to new avenues for targeting treatment of these disorders. Using lentivirally mediated RNA interference (RNAi) against native prion protein (PrP), White et al. report the first therapeutic intervention that results in neuronal rescue, prevents symptoms and increases survival in mice with established prion disease.(1) Both the target and the timing of treatment here are crucial to the effectiveness of this strategy: the formation of the neurotoxic prion agent is prevented at a point when diseased neurons can still be saved from death. But the data also give new insights into the timing of treatment in the context of the pattern of spread of prion infection throughout the brain, with implications for developing the most effective treatments.

Nonallele-specific silencing of mutant and wild-type huntingtin demonstrates therapeutic efficacy in Huntington's disease mice

Huntington's disease (HD) is a fatal neurodegenerative disease caused by mutant huntingtin (htt) protein, and there are currently no effective treatments. Recently, we and others demonstrated that silencing mutant htt via RNA interference (RNAi) provides therapeutic benefit in HD mice. We have since found that silencing wild-type htt in adult mouse striatum is tolerated for at least 4 months. However, given the role of htt in various cellular processes, it remains unknown whether nonallele-specific silencing of both wild-type and mutant htt is a viable therapeutic strategy for HD. Here, we tested whether cosilencing wild-type and mutant htt provides therapeutic benefit and is tolerable in HD mice. After treatment, HD mice showed significant reductions in wild-type and mutant htt, and demonstrated improved motor coordination and survival. We performed transcriptional profiling to evaluate the effects of reducing wild-type htt in adult mouse striatum. We identified gene expression changes that are concordant with previously described roles for htt in various cellular processes. Also, several abnormally expressed transcripts associated with early-stage HD were differentially expressed in our studies, but intriguingly, those involved in neuronal function changed in opposing directions. Together, these encouraging and surprising findings support further testing of nonallele-specific RNAi therapeutics for HD.

Combined antiviral activity of interferon-alpha and RNA interference directed against hepatitis C without affecting vector delivery and gene silencing

The current standard interferon-alpha (IFN-α)-based therapy for chronic hepatitis C virus (HCV) infection is only effective in approximately half of the patients, prompting the need for alternative treatments. RNA interference (RNAi) represents novel approach to combat HCV by sequence-specific targeting of viral or host factors involved in infection. Monotherapy of RNAi, however, may lead to therapeutic resistance by mutational escape of the virus. Here, we proposed that combining lentiviral vector-mediated RNAi and IFN-α could be more effective and avoid therapeutic resistance. In this study, we found that IFN-α treatment did not interfere with RNAi-mediated gene silencing. RNAi and IFN-α act independently on HCV replication showing combined antiviral activity when used simultaneously or sequentially. Transduction of mouse hepatocytes in vivo and in vitro was not effected by IFN-α treatment. In conclusion, RNAi and IFN-α can be effectively combined without cross-interference and may represent a promising combinational strategy for the treatment of hepatitis C.

Treatment of dystonia

Dystonia varies in severity from simple focal dystonia, such as writer's cramp to life-threatening status dystonicus. Even though the pathophysiology is still elusive, symptomatic treatments may provide marked relief. Botulinum toxin is considered the treatment of choice for most focal and segmental dystonias. Deep brain stimulation of the basal ganglia, particularly the globus pallidus internum, is emerging as an important treatment for refractory, generalized, and segmental forms of dystonia. Gene therapy is also being explored as a possible treatment of inherited dystonias. This article reviews the therapeutic options available for the various types of dystonia.

Therapeutic applications of RNAi for silencing virus replication

RNA interference (RNAi) is an evolutionarily conserved gene-silencing mechanism in which small 19-23-nucleotide double-stranded RNA molecules, or small interfering RNAs (siRNAs), target cognate RNA for destruction with exquisite potency and selectivity. The RNAi machinery is believed to be expressed in all eukaryotic cells and has been shown to regulate host gene expression. Given this ability, RNAi silencing strategies have been developed to inhibit viral genes and replication in host cells. One area of growing interest is the development of synthetic siRNA drugs to target acute viral infections in which long-term gene silencing is not required or desirable. To achieve synthetic siRNA drug efficacy, these anti-viral agents need to be delivered to the appropriate host cells, as they do not readily cross the cell membrane. Varied delivery and siRNA chemical stabilization strategies are being investigated for siRNA drug delivery; however, several studies have shown that naked, unmodified siRNA drugs can be effective in silencing replication of some viruses in animal models of infection. These findings suggest that RNAi-based drugs may offer breakthrough technology to protect and treat humans and animals from viral infection. However, there are four major considerations for evaluating successful RNAi efficacy: the siRNAs must have high efficiency, show low cytotoxicity, result in minimal off-target effects, and lead to results that are reproducible between experiments. The methods and caveats to achieve these goals are discussed.