Huntington's disease (HD) is a fatal, neurodegenerative disorder resulting from an expanded tri-nucleotiderepeat (CAG) in exon 1 of the HD gene (HTT). The glutamine expansion in the encoded protein, huntingtin(HTT) confers a toxic gain of function, causing degeneration of neurons in many brain regions, particularly inthe striatum. Because these brain regions are involved with various aspects of motor programming andcognition, HD patients experience many symptoms including chorea (involuntary dance-like movements of thelimbs and neck), loss of short-term memory and emotional disturbances that can include anxiety, depressionand aggression. RNA interference (RNAi) has recently emerged as a leading candidate approach to reduceexpression of disease genes by degrading the encoding mRNA. While normal huntingtin plays a vital role indevelopment, we have demonstrated that a partial (60%) non-allele specific reduction in HTT expression isboth well tolerated and therapeutically beneficial in adult HD transgenic mice. Here, we propose to test theefficiency, safety and therapeutic benefit of this approach in the nonhuman primate (NHP) as a pre-clinical steptowards developing RNAi as a therapy for HD patients.
We first aim to characterize the efficiency and safety ofnon-allele specific RNAi targeting HTT mRNA in the normal NHP brain as a proof-of-principle. Rhesusmacaques (n=4) will receive unilateral, stereotaxic injections into the striatum of a recombinant viral vector thatexpresses mi2.4 (rAAV-mi2.4), a HTT-specific microRNA. The opposite hemisphere will be injected with acontrol miRNA (rAAV-miMIS) that does not reduce HTT expression. Animals will undergo behavioral evaluationto assess the efficacy and tolerability of this approach. Three months post-injection, animals will be euthanizedand brains will be examined for silencing efficiency and several different safety profiles. Next, we aim toestablish a NHP model of HD that includes motor dysfunction, cognitive deficits and emotional manifestations.Rhesus monkeys will receive injections into the striatum of a virus expressing a fragment of mutant HTT(mHTT) with 82 CAG repeats (rAAV-mHTT82Q, n=4) or a control fragment of mHTT with only 18 repeats(rAAV-mHTT-18Q, n=4). This strategy has been previously utilized to create a successful rodent model of HD.Animals will evaluated monthly on a variety of motor, cognitive and psychological assays. Six months post-injection, animals will be euthanized and their brains will be analyzed for signs of HD pathology. Lastly, we aimto test the therapeutic benefit of RNAi in the NHP model of HD. NHPs will be co-injected into the striatum withrAAV-mi2.4 (n=4) or rAAV-miMIS (n=4) along with rAAV-mHTT82Q. Animals will be evaluated monthly on avariety of motor, cognitive and psychological assays. Upon sacrifice at 6 months post-injection, brains will beanalyzed for the prevention of HD-related pathology. Together, these studies will assess the safety andtherapeutic benefit of RNAi in the NHP brain. The studies proposed here, along with the didactic and appliedtraining, will be invaluable in assisting my transition from a post-doctoral fellow to an independent investigator.

Public Health Relevance

The proposed set of studies aims at testing the benefit of RNA interference as a potential therapy for Huntington's disease (HD). There is no cure for this devastating, fatal disease and currently 30,000 people are affected in the United States alone. Testing the utility of RNA interference in a nonhuman primate model of HD is a necessary and key step towards its potential use in the clinic.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Transition Award (R00)
Project #
4R00NS069798-02
Application #
8270977
Study Section
Special Emphasis Panel (NSS)
Program Officer
Sutherland, Margaret L
Project Start
2011-06-15
Project End
2014-05-31
Budget Start
2011-06-15
Budget End
2012-05-31
Support Year
2
Fiscal Year
2011
Total Cost
$249,000
Indirect Cost
Name
Oregon Health and Science University
Department
Other Basic Sciences
Type
Other Domestic Higher Education
DUNS #
096997515
City
Portland
State
OR
Country
United States
Zip Code
97239