Lowering Mutant Huntingtin Using Tricyclo-DNA Antisense Oligonucleotides As a Therapeutic Approach for Huntington's Disease

Nucleic Acid Ther. 2019 Oct;29(5):256-265. doi: 10.1089/nat.2018.0775. Epub 2019 Jun 11.


Huntington's disease is a neurodegenerative disorder caused by a CAG repeat expansion in the first exon of huntingtin gene (HTT) encoding for a toxic polyglutamine protein. This disease is characterized by motor, psychiatric, and cognitive impairments. Currently, there is no disease modifying treatment. However, reducing the expression of the huntingtin protein (HTT) using antisense oligonucleotides (ASOs) has been shown as a promising therapeutic strategy. In this study, we explore the therapeutic potential of ASO made of tricyclo-DNA (tcDNA), a conformationally constrained DNA analog, to silence HTT. We used a gapmer ASO, containing central DNA nucleotides flanked by tcDNA modifications on 5' and 3' ends, allowing the recruitment of RNAse H and subsequent degradation of the messenger RNA. After transfection of tcDNA-ASO in patient-derived fibroblast cell lines, we show a strong decrease of HTT mRNA and protein levels. As a control, 2'O-methyl-RNA targeting the same region of HTT was also tested and did not induce a significant effect. tcDNA-ASO were also evaluated in vivo in the YAC128 mice, containing the full-length human HTT gene with 128 CAG repeat expansion. Single intracerebroventricular (ICV) injections of tcDNA induce a significant decrease of HTT messenger and protein levels in the cortex, hippocampus, striatum, and cerebellum of treated mice. tcDNA-ASO were found well distributed in the central nervous system (CNS) and show long lasting effect with protein levels still low, 12 weeks after a single ICV injection. This proof of concept study suggests the therapeutic potential of gapmer tcDNA ASO to downregulate huntingtin in vitro and in vivo.

Keywords: Huntington disease; antisense oligonucleotides; tcDNA-ASOs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • DNA, Antisense / pharmacology
  • Disease Models, Animal
  • Exons / genetics
  • Humans
  • Huntingtin Protein / antagonists & inhibitors
  • Huntingtin Protein / genetics*
  • Huntington Disease / genetics
  • Huntington Disease / immunology
  • Huntington Disease / pathology
  • Huntington Disease / therapy*
  • Mice
  • Mutant Proteins / antagonists & inhibitors
  • Mutant Proteins / genetics*
  • Oligonucleotides, Antisense / genetics
  • Oligonucleotides, Antisense / pharmacology*
  • Ribonuclease H / genetics
  • Trinucleotide Repeat Expansion / genetics


  • DNA, Antisense
  • HTT protein, human
  • Huntingtin Protein
  • Mutant Proteins
  • Oligonucleotides, Antisense
  • Ribonuclease H