Background Different therapeutic approaches using antisense oligonucleotides (AONs) are currently under development for Huntington’s disease (HD). Ideally, an AON-based therapeutic approach for HD would selectively lower levels of the transcript carrying the disease-causing CAG-repeat expansion, but not affect the non-expanded transcript. We have previously demonstrated preferential knockdown of the mutant transcript in vitroin fibroblasts derived from HD patients using a CAG-repeat targeting AON consisting of a (CUG)7 sequence.
Aims Aim of this study was to gain in vivoproof-of-concept with our (CUG)7 AON in a relevant HD animal model.
Methods/techniques R6/2 mice transgenic for an N-terminal fragment of human HTT containing ˜150 CAG repeats (n = 30) received a total of 6 weekly ICV infusions with the (CUG)7 AON or vehicle. Bodyweight was monitored and a battery of motor tests (grip strength, rotarod, open field, 3D kinematic analysis) were performed. In addition, brain volume and striatal metabolites were quantified using MRI and MRS respectively. Two weeks after the last infusion at 12 weeks of age RNA was isolated from 7 different brain regions, followed by RT-qPCR analysis of HTT transcript levels.
Results/outcome A highly signficant and strong (˜90%) reduction of mutant HTT mRNA levels was observed throughout the R6/2 brain. In addition, there was a clear positive treatment effect on motor performance, indicated by an increase in rotarod latency and vertical activity in the open field. 3D kinematic analysis of fine motor skills showed a significant improvement of several parameters impaired in R6/2 mice. A trend towards an increased whole brain and cortical volume was observed using MRI volumetry as well as a significant decrease in striatal levels of the astrocytic marker inositol, known to be elevated in the striatum of R6/2 mice and HD patients.
Conclusions These data demonstrate our AON targeting the CAG-repeat has therapeutic potential for HD.
- antisense oligonucleotides
- HTT-lowering therapeutics
- in vivo