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.
"Animal models of idiopathic Parkinson's disease have been extensively treated by protection of dopaminergic neurons through overexpression of trophic factors (GDNF) in the substantia nigra    or alternatively through expression of enzymes for dopamine synthesis in surviving cells of the striatum  or GABA in the subthalamic nucleus . In Huntington's diseases models, although a trophic approach has also been extensively explored , a more precise line aimed at silencing the mutant Huntingtin gene in the GABAergic medium spiny neurons of the striatum was explored   . As for these and other prototypical gene therapy approaches, the modeled disease could be slowed they subsequently have been, or are being, progressively scaled-up for translational therapies in humans  . "
"shCDK5miR and shSCRmiR expression cassettes, driven by the mouse U6 promoter, were cloned into pAAV.CMV.humanized Renilla GFP (hrGFP), which contains AAV serotype 2/5 inverted terminal repeats, and a CMV-hrGFP-simian virus 40 poly(A) reporter cassette (Urabe et al., 2002; Boudreau et al., 2009). AAV titers were determined by using quantitative PCR and/or DNA slot blot analysis. "
[Show abstract][Hide abstract] ABSTRACT: CDK5 is a member of the cyclin-dependent kinase family with diverse functions in both the developing and mature nervous system. The inappropriate activation of CDK5 due to the proteolytic release of the activator fragment p25 from the membrane contributes to the formation of neurofibrillary tangles and chronic neurodegeneration. At 18 months of age 3xTg-AD mice were sacrificed after 1 year (long term) or 3 weeks (short term) of CDK5 knockdown. In long-term animals CDK5 knockdown prevented insoluble Tau formation in the hippocampi and prevented spatial memory impairment. In short-term animals, CDK5 knockdown showed reduction of CDK5, reversed Tau aggregation, and improved spatial memory compared to scrambled treated old 3xTg-AD mice. Neither long-term nor short-term CDK5 knock-down had an effect on old littermates. These findings further validate CDK5 as a target for Alzheimer's disease both as a preventive measure and after the onset of symptoms.
"There are some studies conducted in HD mouse models that support the idea that reducing both wt and mHTT is well tolerated and leads to clinical benefit –. However, alterations in molecular pathways associated with loss of normal HTT function have also been observed , . It is very difficult to predict how these findings may translate into human applications. "
[Show abstract][Hide abstract] ABSTRACT: 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.
PLoS ONE 09/2014; 9(9):e107434. DOI:10.1371/journal.pone.0107434 · 3.23 Impact Factor
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