. Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder, characterized by relentless progression to death ~20 years after disease onset. HD is caused by an expanded CAG repeat in exon 1 of the huntingtin (HTT) gene. Disease pathogenesis is largely a result of expression of the mutant transcript and protein, which have neurotoxic properties. Suppressing the expression of the mutant allele is therefore a promising therapeutic approach, thus far pursued with antibody, oligonucleotide and siRNA strategies. As with any knockdown approach, especially in the CNS, problems of delivery, reversibility, and off-target effects using these methods remain problematic. Surprisingly, relatively little is known about the regulation of the HD locus, and in particular on the mechanisms that regulate HTT expression. We have recently discovered a gene on the strand antisense to HTT at the HD locus, which we have termed huntingtin antisense (HTT-AS). We have demonstrated that increasing expression of HTT-AS decreases expression of HTT, and that HTT-AS expression can be manipulated using small molecules. We hypothesize that HTT-AS itself, and the components that regulate its expression and interaction with HTT, will provide novel therapeutic targets for suppression of HTT expression and hence treatment of HD. A corollary to this hypothesis is that a better understanding of the HD locus, in this case the role of HTT-AS, will be critical in the interpretation of any HTT suppression strategy. We will test this hypothesis with a series of experiments organized into three specific aims, each built on compelling preliminary data.
In Aim 1, we will determine if additional HTT-AS exons, splice variants, and promoters exist, determine the effect of repeat expansion on HTT-AS expression, and identify protein factors that regulate HTT-AS promoter activity.
In Aim 2, we will determine the mechanisms by which HTT-AS suppresses HTT, including the quantitative effect of different HTT-AS transcripts on the suppression of HTT, and the role of chromatin remodeling on HTT expression.
In Aim 3, we will collaborate with NCATS and CHDI to perform a large scale high throughput screen to find and characterize compounds that decrease expression of HTT by specifically increasing expression of HTT-AS. Selected compounds will be validated in cell and mouse models.

Public Health Relevance

. Huntington's disease (HD) is a devastating adult-onset hereditary neurodegenerative disorder, caused by a mutation in the gene huntingtin, for which there is no treatment. We propose to explore the possibility that mutant huntingtin can be suppressed by small molecules that increase the expression of the huntingtin antisense gene. The proposed experiments may lead to novel potential therapeutic agents for the treatment of HD.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS100783-04
Application #
9963423
Study Section
Molecular Neurogenetics Study Section (MNG)
Program Officer
Miller, Daniel L
Project Start
2017-09-15
Project End
2022-06-30
Budget Start
2020-07-01
Budget End
2021-06-30
Support Year
4
Fiscal Year
2020
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Psychiatry
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21205