AAV-based delivery of RNAi targeting Ataxin-2 improves survival, strength, and pathology in mouse models of rapidly and slowly progressive sporadic ALS.

Amyotrophic lateral sclerosis (ALS) is characterized by motor neuron death due to nuclear loss and cytoplasmic aggregation of the splice factor TDP-43. Pathologic TDP-43 associates with stress granules (SGs) and downregulating the SG-associated protein Ataxin-2 (Atxn2) using antisense oligonucleotides (ASO) prolongs survival in the TAR4/4 sporadic ALS mouse model, a strategy now in clinical trials. Here, we used AAV-mediated RNAi delivery to achieve lasting and targeted Atxn2 knockdown after a single injection. To achieve this, a novel AAV with improved transduction potency of our target cells was used to deliver Atxn2 -targeting miRNAs. Mouse dosing studies demonstrated 55% Atxn2 knockdown in frontal cortex and 25% knockdown throughout brainstem and spinal cord after intracerebroventricular injection at a dose 40x lower than used in other recent studies. In TAR4/4 mice, miAtxn2 treatment increased mean and median survival by 54% and 45% respectively (p<0.0003). Mice showed robust improvement across strength-related measures ranging from 24-75%. Interestingly, treated mice showed increased vertical activity above wildtype, suggesting unmasking of an FTD phenotype with improved strength. Histologically, lower motor neuron survival improved with a concomitant reduction in CNS inflammatory markers. Additionally, phosphorylated TDP-43 was reduced to wildtype levels. Bulk RNA sequencing revealed correction of 153 genes in the markedly dysregulated transcriptome of mutant mice, several of which are described in the human ALS literature. In slow progressing hemizygous mice, treatment rescued weight loss and improved gait at late time points. Cumulatively the data support the utility of AAV-mediated RNAi against Atxn2 as a robust and translatable treatment strategy for sporadic ALS.

Huntington's disease phenotypes are improved via mTORC1 modulation by small molecule therapy.

Huntington's Disease (HD) is a dominantly inherited neurodegenerative disease for which the major causes of mortality are neurodegeneration-associated aspiration pneumonia followed by cardiac failure. mTORC1 pathway perturbations are present in HD models and human tissues. Amelioration of mTORC1 deficits by genetic modulation improves disease phenotypes in HD models, is not a viable therapeutic strategy. Here, we assessed a novel small molecule mTORC1 pathway activator, NV-5297, for its improvement of the disease phenotypes in the N171-82Q HD mouse model. Oral dosing of NV-5297 over 6 weeks activated mTORC1, increased striatal volume, improved motor learning and heart contractility. Further, the heart contractility, heart fibrosis, and survival were improved in response to the cardiac stressor isoprenaline when compared to vehicle-treated mice. Cummulatively, these data support mTORC1 activation as a therapeutic target in HD and consolidates NV-5297 as a promising drug candidate for treating central and peripheral HD phenotypes and, more generally, mTORC1-deficit related diseases.

Temporal Phenotypic Changes in Huntington's Disease Models for Preclinical Studies.

BACKGROUND: Mouse models bearing genetic disease mutations are instrumental in the development of therapies for genetic disorders. Huntington's disease (HD) is a late-onset lethal dominant genetic disorder due to a CAG repeat within exon 1 of the Huntingtin (Htt) gene. Several mice were developed to model HD through the expression of a transgenic fragment (exon 1 of the human HTT), the knock-in mutation of the CAG repeat in the context of the mouse Htt gene, or the full-length HTT human gene. The different mouse models present distinct onset, symptoms, and progression of the disease. OBJECTIVE: The objective of this study is to advise on the best behavioral tests to assess disease progression in three HD mouse models. METHODS: We tested N171-82Q transgenic mice, zQ175 knock-in mice, and BACHD full-length mice in a comprehensive behavior test battery in early, mid-, and late disease stages. RESULTS: We contrast and compare the models and the emerging phenotypes with the available literature. These results suggest the most effective behavioral tests and appropriate sample sizes to detect treatment efficacy in each model at the different ages. We provide options for early detection of motor deficits while minimizing testing time and training. CONCLUSION: This information will inform researchers in the HD field as to which mouse model, tests and sample sizes can accurately and sensitively detect treatment efficacy in preclinical HD research.