Proteolysis resistant huntingtin isoform induced by antisense oligonucleotide maintains normal huntingtin function in mouse

Huntington’s disease (HD) is a late onset neurological disorder for which no neuroprotective therapies efficiently delay onset or progression. A key pathological mechanism in disease involves the proteolysis of polyglutamine (polyQ)-expanded mutant huntingtin (mHTT) generating polyQ-containing N-terminal fragments that are crucial contributors to HD pathogenesis since inhibition of the cleavage at the putative caspase-6 site reduces pathology in a HD mouse model. Interestingly, a naturally occurring alternative spliced form of HTT lacking exon12 (HTTΔ12) leads to a protein with an internal deletion of the caspase-6 N-terminal cleavage site. Here, we have taken a multidisciplinary approach to characterize the therapeutic potential of targeting exon12 of HTT. We show that HTTΔ12 is fully resistant to caspase-6 cleavage in both cell-free and tissue lysate assays, while maintaining overall biochemical and structural properties similar to wild-type (wt)-HTT. We generated mouse deleted for exon12 and found that exon12 is dispensable for HTT main physiological functions including embryonic development and intracellular trafficking such as BDNF transport. Finally, we pharmacologically induced HTTΔ12 using an antisense oligonucleotide (ASO). QRX-704 ASO efficiently distributes in the whole brain, is stable several months, and reduces pathogenic proteolysis. Thus, ASO-induced exon12 deletion of HT We performed gene expression profiling analysis using data obtained from RNA-seq of brain tissue (cortex and striatum) samples originating from mouse littermates from HttΔ12 (Δ12;KI) and HttKO (KO) lines at 3 month of age. Comparative gene expression profiling analysis of RNA-seq data for c57BL/6N mouse adult HttΔ12 brain.