Huntington disease (HD) is an inherited, fatal neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin gene. The mutant protein causes neuronal dysfunction and degeneration resulting in motor dysfunction, cognitive decline, and psychiatric disturbances. Currently, there is no disease altering treatment, and symptomatic therapy has limited benefit. The pathogenesis of HD is complicated and multiple pathways are compromised. Addressing the problem at its genetic root by suppressing mutant huntingtin expression is a promising therapeutic strategy for HD. We have developed and evaluated antisense oligonucleotides (ASOs) targeting single nucleotide polymorphisms that are significantly enriched on HD alleles (HD-SNPs). We describe our structure-activity relationship studies for ASO design and find that adjusting the SNP position within the gap, chemical modifications of the wings, and shortening the unmodified gap are critical for potent, specific, and well tolerated silencing of mutant huntingtin. Finally, we show that using two distinct ASO drugs targeting the two allelic variants of an HD-SNP could provide a therapeutic option for all persons with HD; allele-specifically for roughly half, and non-specifically for the remainder.
The long non-coding RNA MALAT1, also known as MALAT-1 or NEAT2, is a highly conserved nuclear ncRNA and a predictive marker for metastasis development in lung cancer. To uncover its functional importance, we developed a MALAT1 knockout model in human lung tumor cells by genomically integrating RNA destabilizing elements using Zinc Finger Nucleases. The achieved 1000-fold MALAT1 silencing provides a unique loss-of-function model. Proposed mechanisms of action include regulation of splicing or gene expression. In lung cancer, MALAT1 does not alter alternative splicing but actively regulates gene expression including a set of metastasis-associated genes. Consequently, MALAT1-deficient cells are impaired in migration and form fewer tumor nodules in a mouse xenograft. Antisense oligonucleotides blocking MALAT1 prevent metastasis formation after tumor implantation. Thus, targeting MALAT1 with antisense oligonucleotides provides a potential therapeutic approach to prevent lung cancer metastasis with MALAT1 serving as both, predictive marker and therapeutic target. Lastly, regulating gene expression, but not alternative splicing is the critical function of MALAT1 in lung cancer metastasis. In summary, ten years after the discovery of the lncRNA MALAT1 as a biomarker for lung cancer metastasis, our loss-of-function model unravels the active function of MALAT1 as a regulator of gene expression governing hallmarks of lung cancer metastasis.
non-coding RNA; MALAT1; lung cancer; metastasis; Zinc Finger Nucleases
Alpha-1 antitrypsin deficiency (AATD) is a rare genetic disease that results from mutations in the alpha-1 antitrypsin (AAT) gene. The mutant AAT protein aggregates and accumulates in the liver leading to AATD liver disease, which is only treatable by liver transplant. The PiZ transgenic mouse strain expresses a human AAT (hAAT) transgene that contains the AATD-associated Glu342Lys mutation. PiZ mice exhibit many AATD symptoms, including AAT protein aggregates, increased hepatocyte death, and liver fibrosis. In the present study, we systemically treated PiZ mice with an antisense oligonucleotide targeted against hAAT (AAT-ASO) and found reductions in circulating levels of AAT and both soluble and aggregated AAT protein in the liver. Furthermore, AAT-ASO administration in these animals stopped liver disease progression after short-term treatment, reversed liver disease after long-term treatment, and prevented liver disease in young animals. Additionally, antisense oligonucleotide treatment markedly decreased liver fibrosis in this mouse model. Administration of AAT-ASO in nonhuman primates led to an approximately 80% reduction in levels of circulating normal AAT, demonstrating potential for this approach in higher species. Antisense oligonucleotides thus represent a promising therapy for AATD liver disease.
Loss-of-function mutations in SMN1 cause spinal muscular atrophy (SMA), a leading genetic cause of infant mortality. The related SMN2 gene expresses suboptimal levels of functional SMN protein, due to a splicing defect. Many SMA patients reach adulthood, and there is also adult-onset (type IV) SMA. There is currently no animal model for adult-onset SMA, and the tissue-specific pathogenesis of post-developmental SMN deficiency remains elusive. Here, we use an antisense oligonucleotide (ASO) to exacerbate SMN2 mis-splicing. Intracerebroventricular ASO injection in adult SMN2-transgenic mice phenocopies key aspects of adult-onset SMA, including delayed-onset motor dysfunction and relevant histopathological features. SMN2 mis-splicing increases during late-stage disease, likely accelerating disease progression. Systemic ASO injection in adult mice causes peripheral SMN2 mis-splicing and affects prognosis, eliciting marked liver and heart pathologies, with decreased IGF1 levels. ASO dose–response and time-course studies suggest that only moderate SMN levels are required in the adult central nervous system, and treatment with a splicing-correcting ASO shows a broad therapeutic time window. We describe distinctive pathological features of adult-onset and early-onset SMA.
adult-onset SMA; pathology; SMN2; spinal muscular atrophy; splicing
The primary cause of Huntington’s disease (HD) is expression of huntingtin with a polyglutamine expansion. Despite an absence of consensus on the mechanism(s) of toxicity, diminishing the synthesis of mutant huntingtin will abate toxicity if delivered to the key affected cells. With antisense oligonucleotides (ASOs) that catalyze RNase H-mediated degradation of huntingtin mRNA, we demonstrate that transient infusion into the cerebral spinal fluid of symptomatic HD mouse models not only delays disease progression, but mediates a sustained reversal of disease phenotype that persists longer than the huntingtin knockdown. Reduction of wild type huntingtin, along with mutant huntingtin, produces the same sustained disease reversal. Similar ASO infusion into non-human primates is shown to effectively lower huntingtin in many brain regions targeted by HD pathology. Rather than requiring continuous treatment, our findings establish a therapeutic strategy for sustained HD disease reversal produced by transient ASO-mediated diminution of huntingtin synthesis.
Genome-wide studies have identified thousands of long noncoding RNAs (lncRNAs) lacking protein coding capacity. However, most lncRNAs are expressed at a very low level, and in most cases there is no genetic evidence to support their in vivo function. Malat1 (metastasis associated lung adenocarcinoma transcript 1) is among the most abundant and highly conserved lncRNAs, and it exhibits an uncommon 3′-end processing mechanism. In addition, its specific nuclear localization, developmental regulation, and dysregulation in cancer are suggestive of it having a critical biological function. We have characterized a Malat1 loss-of-function genetic model that indicates Malat1 is not essential for mouse pre- and post-natal development. Furthermore, depletion of Malat1 does not impact global gene expression, splicing factor level and phosphorylation status, or alternative pre-mRNA splicing. However, among a small number of genes that were dysregulated in adult Malat1 knockout mice, many were Malat1 neighboring genes, thus indicating a potential cis regulatory role of Malat1 gene transcription.
Wig-1 is a transcription factor regulated by p53 that can interact with hnRNP A2/B1, RNA Helicase A, and dsRNAs, which plays an important role in RNA and protein stabilization. in vitro studies have shown that wig-1 binds p53 mRNA and stabilizes it by protecting it from deadenylation. Furthermore, p53 has been implicated as a causal factor in neurodegenerative diseases based in part on its selective regulatory function on gene expression, including genes which, in turn, also possess regulatory functions on gene expression. In this study we focused on the wig-1 transcription factor as a downstream p53 regulated gene and characterized the effects of wig-1 down regulation on gene expression in mouse liver and brain.
Methods and Results
Antisense oligonucleotides (ASOs) were identified that specifically target mouse wig-1 mRNA and produce a dose-dependent reduction in wig-1 mRNA levels in cell culture. These wig-1 ASOs produced marked reductions in wig-1 levels in liver following intraperitoneal administration and in brain tissue following ASO administration through a single striatal bolus injection in FVB and BACHD mice. Wig-1 suppression was well tolerated and resulted in the reduction of mutant Htt protein levels in BACHD mouse brain but had no effect on normal Htt protein levels nor p53 mRNA or protein levels. Expression microarray analysis was employed to determine the effects of wig-1 suppression on genome-wide expression in mouse liver and brain. Reduction of wig-1 caused both down regulation and up regulation of several genes, and a number of wig-1 regulated genes were identified that potentially links wig-1 various signaling pathways and diseases.
Antisense oligonucleotides can effectively reduce wig-1 levels in mouse liver and brain, which results in specific changes in gene expression for pathways relevant to both the nervous system and cancer.
Mice deficient for the cellular prion protein (PrPC) do not develop prion disease; accordingly, gene-based strategies to diminish PrPC expression are of interest. We synthesized a series of chemically modified antisense oligonucleotides (ASOs) targeted against mouse Prnp messenger RNA (mRNA) and identified those that were most effective in decreasing PrPC expression. Those ASOs were also evaluated in scrapie-infected cultured cells (ScN2a) for their efficacy in diminishing the levels of the disease-causing prion protein (PrPSc). When the optimal ASO was infused intracerebrally into FVB mice over a 14-day period beginning 1 day after infection with the Rocky Mountain Laboratory (RML) strain of mouse prions, a prolongation of the incubation period of almost 2 months was observed. Whether ASOs can be used to develop an effective therapy for patients dying of Creutzfeldt–Jakob disease remains to be established.
Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by mutations in the SMN1 gene that result in a deficiency of SMN protein. One approach to treat SMA is to use antisense oligonucleotides (ASOs) to redirect the splicing of a paralogous gene, SMN2, to boost production of functional SMN. Injection of a 2′-O-2-methoxyethyl–modified ASO (ASO-10-27) into the cerebral lateral ventricles of mice with a severe form of SMA resulted in splice-mediated increases in SMN protein and in the number of motor neurons in the spinal cord, which led to improvements in muscle physiology, motor function and survival. Intrathecal infusion of ASO-10-27 into cynomolgus monkeys delivered putative therapeutic levels of the oligonucleotide to all regions of the spinal cord. These data demonstrate that central nervous system–directed ASO therapy is efficacious and that intrathecal infusion may represent a practical route for delivering this therapeutic in the clinic.
Activation of the spinal phospholipase A2 (PLA2) - cyclooxygenase (COX) – prostaglandin signaling pathway is widely implicated in nociceptive processing. Although the role of spinal COX isoforms in pain signal transmission has been extensively characterized, our knowledge of PLA2 enzymes in this cascade is limited. Among all PLA2 groups, cytosolic calcium-dependent PLA2 group IVA (cPLA2IVA) appears to be the predominant PLA2 enzyme in the spinal cord. In the present study we sought to (i) characterize anatomical and cellular distribution and localization of cPLA2IVA in dorsal horn of rat spinal cord, (ii) verify efficacy and selectivity of intrathecal (IT) delivery of an antisense oligonucleotide (AS) targeting rat cPLA2IVA mRNA on spinal expression of this enzyme, and (iii) examine the effect of down-regulation of spinal cPLA2IVA on peripheral tissue injury-induced pain behavior. Here we demonstrate that cPLA2IVA is constitutively expressed in rat spinal cord, predominantly in dorsal horn neurons and oligodendrocytes but not in astrocytes or microglia. Intrathecal injection of AS significantly down-regulated both protein and gene expression of cPLA2IVA in rat spinal cord, while control missense oligonucleotide (MS) had no effect. Immunocytochemistry confirmed that the reduction occurred in neurons and oligodendrocytes. cPLA2IVA.AS did not alter expression of several other PLA2 isoforms, such as secretory PLA2 (groups IIA and V) and calcium-independent PLA2 (group VI), indicating that the AS was specific for cPLA2IVA. This selective knockdown of spinal cPLA2IVA did not change acute nociception (i.e. paw withdrawal thresholds to acute thermal stimuli and intradermal formalin-induced first phase flinching), however, it significantly attenuated formalin-induced hyperalgesia (i.e. second phase flinching behavior), which reflects spinal sensitization. Thus the present findings suggest that cPLA2IVA may specifically participate in spinal nociceptive processing.
Rat; Intrathecal; Neurons; Oligodendrocytes; Pain
A series of antisense oligonucleotides (ASOs) containing either 2′-O-methoxyethylribose (MOE) or locked nucleic acid (LNA) modifications were designed to investigate whether LNA antisense oligonucleotides (ASOs) have the potential to improve upon MOE based ASO therapeutics. Some, but not all, LNA containing oligonucleotides increased potency for reducing target mRNA in mouse liver up to 5-fold relative to the corresponding MOE containing ASOs. However, they also showed profound hepatotoxicity as measured by serum transaminases, organ weights and body weights. This toxicity was evident for multiple sequences targeting three different biological targets, as well as in mismatch control sequences having no known mRNA targets. Histopathological evaluation of tissues from LNA treated animals confirmed the hepatocellular involvement. Toxicity was observed as early as 4 days after a single administration. In contrast, the corresponding MOE ASOs showed no evidence for toxicity while maintaining the ability to reduce target mRNA. These studies suggest that while LNA ASOs have the potential to improve potency, they impose a significant risk of hepatotoxicity.
Neurotoxicity from accumulation of misfolded/mutant proteins is thought to drive pathogenesis in neurodegenerative diseases. Since decreasing levels of proteins responsible for such accumulations is likely to ameliorate disease, a therapeutic strategy has been developed to downregulate almost any gene in the CNS. Modified antisense oligonucleotides, continuously infused intraventricularly, have been demonstrated to distribute widely throughout the CNS of rodents and primates, including the regions affected in the major neurodegenerative diseases. Using this route of administration, we found that antisense oligonucleotides to superoxide dismutase 1 (SOD1), one of the most abundant brain proteins, reduced both SOD1 protein and mRNA levels throughout the brain and spinal cord. Treatment initiated near onset significantly slowed disease progression in a model of amyotrophic lateral sclerosis (ALS) caused by a mutation in SOD1. This suggests that direct delivery of antisense oligonucleotides could be an effective, dosage-regulatable means of treating neurodegenerative diseases, including ALS, where appropriate target proteins are known.
The colony formation assay is the most commonly used titration method for defining the concentration of replication-incompetent murine leukemia virus-derived retroviral vectors. However, titer varies with target cell type and number, transduction time, and concentration of polycation (e.g., Polybrene). Moreover, because most of the viruses cannot encounter target cells due to Brownian motion, their short half-lives, and the requirement for target cell division for activity, the actual infectious retrovirus concentration in the collected supernatant is higher than the viral titer. Here we correlate the physical viral particle concentration with the infectious virus concentration and colony formation titer with the help of a mathematical model. Ecotropic murine leukemia retrovirus supernatant, collected from the GP+E86/LNCX retroviral vector producer cell line, was concentrated by centrifugation and further purified by a sucrose density gradient. The physical concentration of purified viral vectors was determined by direct particle counting with an electron microscope. The concentrations of fresh and concentrated supernatant were determined by a quantitative reverse transcriptase activity assay. Titration of all supernatants by neomycin-resistant colony formation assay was also performed. There were 767 ± 517 physical viral particles per infectious CFU in the crude viral supernatant. However, the infectious viral concentration determined by mathematical simulation was 143 viral particles per infectious unit, which is more consistent with the concentration determined by particle counting in purified viral solution. Our results suggest that the mathematical model can be used to extract a more accurate and reliable concentration of infectious retrovirus.