After 4 years of hard work, our paper “Antisense oligonucleotide-induced amyloid precursor protein splicing modulation as a therapeutic approach for Dutch-type cerebral amyloid angiopathy” has been published in Nucleic Acid Therapeutics (DOI: 10.1089/nat.2021.0005).
In this study we explored the use of an antisense oligonucleotide (AON) as a therapeutic approach for Dutch-type cerebral amyloid angiopathy (D-CAA), a rare brain disease characterized by recurring strokes and vascular dementia. The disease is caused by a point mutation on exon 17 of amyloid precursor protein (APP) gene. The missense variant is located in the Aβ domain of APP. After cleavage of APP by β- and γ-secretases the Aβ peptide produced is more prone to aggregation. Together with an impaired clearance from the brain, toxic Aβ aggregates are formed in the cerebral leptomeningeal arteries and cortical arterioles.
We demonstrated that when using an AON targeting exon 17, which contains both the Dutch mutation and the γ-secretase cleavage site, exon 17 is skipped and leads to production of a new APP isoform (ΑPPΔ17) that lacks part of the Aβ domain, thus preventing Aβ accumulation. First we showed successful exon 17 skipping on RNA level and APPΔ17 isoform generation on protein level in vitro with a simultaneous decrease in Aβ40 and Aβ42 levels in medium of neuronally-induced pluripotent stem cells (iPSCs). Then, we showed an effect of the AON on RNA and protein levels in vivo in wt-mice. An interesting aspect that came from the in vivo study was that when shortening the AON from 33 nucleotides to 20 nucleotides we saw significantly higher protein modification, meaning that the brain uptake of AON is better with a shorter AON length.
This work was done in collaboration with the start-up Amylon Therapeutics (Leiden) and with Dr. Marcel Verbeek (Radboud UMC, Nijmegen).