Limited early successes in liver-based RNA interference (RNAi) therapies are enabling additional pre-clinical and clinical approaches. As with any therapeutic, achieving a functional effect is tempered by toxic side effects when a high RNAi dose is delivered. Toxicity and even fatality from high-level transcriptional RNAi based preclinical studies in mice was first reported by our group and confirmed by others. During the last 5 years, we made important contributions to our basic understanding of microRNA biology including pri/pre-miRNA processing, mechanism of Dicer cleavage, and properties related to miRNA-RISC loading. These studies have resulted in improved RNAi design strategies aimed at increasing efficacy and minimizing toxicity, especially those geared towards better treatments for HBV and HCV infection. Similar but distinct from RNAi, antisense oligonucleotide clinical trials are gaining in popularity includig targeting the highly abundant liver-specific miR- 122 (70% of liver miRNAs) to prevent HCV replication. We recently found that the newly transcribed miR-122- 5p-22nt miRNA isoform was selectively displaced from active RISC complexes after AAV-U6-shRNA delivery and that the functional reduction in miR-122 was responsible for the toxicity. We plan to investigate the mechanism(s) involved in how these changes in miR-122 occur and lead to toxicity. We propose a competition model where the shRNAs transcribed from a DNA template displaces miR122, which then causes both an up regulation of genes containing a miR122 target and altered transcription from the miR122 gene locus ultimately disrupting normal hepatocyte homeostasis and inducing liver injury. We also believe that precursor transcripts from the miR122 locus - a set of long-noncoding RNAs are not merely a set of precursor intermediates but have separate functions in cellular programming. We will use a variety of genetic tools and various mouse models to uncouple the expression of the various RNAs derived from the miR122 locus and determine their effect on gene regulation, hepatocyte homeostasis, and growth states. We will also evaluate the possible regulatory role that the miR122 gene has on the activation of the chr12qF1 microRNA locus implicated in the formation of hepatocellular carcinoma. In total, our proposal will further unravel the mechanism(s) of RNAi-induced toxicity and define the biological function of the most highly expressed and tissue specific miRNA gene locus- miR122 in healthy and diseased liver states.

Public Health Relevance

RNAi therapeutics shows promise for treating various infectious and genetic diseases. We will define specific limits to RNAi therapies and how miRNA metabolism and liver homeostasis is perturbed when these limits are exceeded. We will also further define the normal biological function of the most highly expressed and tissue specific miRNA genetic locus- miR-122 in healthy & diseased liver states.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Therapeutic Approaches to Genetic Diseases Study Section (TAG)
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Koshy, Rajen
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Stanford University
Schools of Medicine
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Valdmanis, Paul N; Kim, Hak Kyun; Chu, Kirk et al. (2018) miR-122 removal in the liver activates imprinted microRNAs and enables more effective microRNA-mediated gene repression. Nat Commun 9:5321
Kim, Hak Kyun; Fuchs, Gabriele; Wang, Shengchun et al. (2017) A transfer-RNA-derived small RNA regulates ribosome biogenesis. Nature 552:57-62
Valdmanis, Paul N; Gu, Shuo; Chu, Kirk et al. (2016) RNA interference-induced hepatotoxicity results from loss of the first synthesized isoform of microRNA-122 in mice. Nat Med 22:557-62
Haussecker, Dirk; Kay, Mark A (2015) RNA interference. Drugging RNAi. Science 347:1069-70
Valdmanis, P N; Roy-Chaudhuri, B; Kim, H K et al. (2015) Upregulation of the microRNA cluster at the Dlk1-Dio3 locus in lung adenocarcinoma. Oncogene 34:94-103
Gu, Shuo; Zhang, Yue; Jin, Lan et al. (2014) Weak base pairing in both seed and 3' regions reduces RNAi off-targets and enhances si/shRNA designs. Nucleic Acids Res 42:12169-76
Roy-Chaudhuri, Biswajoy; Valdmanis, Paul N; Zhang, Yue et al. (2014) Regulation of microRNA-mediated gene silencing by microRNA precursors. Nat Struct Mol Biol 21:825-32
Gu, Shuo; Jin, Lan; Zhang, Yue et al. (2012) The loop position of shRNAs and pre-miRNAs is critical for the accuracy of dicer processing in vivo. Cell 151:900-911
Parameswaran, Poornima; Sklan, Ella; Wilkins, Courtney et al. (2010) Six RNA viruses and forty-one hosts: viral small RNAs and modulation of small RNA repertoires in vertebrate and invertebrate systems. PLoS Pathog 6:e1000764
Grimm, Dirk; Wang, Lora; Lee, Joyce S et al. (2010) Argonaute proteins are key determinants of RNAi efficacy, toxicity, and persistence in the adult mouse liver. J Clin Invest 120:3106-19

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