Poster Presentation 39th Annual Lorne Genome Conference 2018

Therapeutic potential of antisense oligonucleotide-mediated exon inclusion for Stargardt disease (#167)

Di Huang 1 2 3 , Sue Fletcher 1 3 , May Aung-Htut 1 3 , Norman Palmer 3 , Fred Chen 2 4 , Steve Wilton 1 3
  1. Molecular Therapy Laboratory, Murdoch University, Perth, Western Australia, Australia
  2. Centre for Ophthalmology and Visual Science & Lions Eye Institute,The University of Western Australia, Perth, Western Australia, Australia
  3. Perron Institute for Neurological and Translational Science, Perth, Western Australia, Australia
  4. Department of Ophthalmology, Royal Perth Hospital, Perth, Western Australia, Australia

Stargardt disease (STGD1) is an autosomal recessive juvenile-onset macular dystrophy caused by mutations in the ATP-binding cassette transporter gene (ABCA4). ABCA4 is localized to the rims of the outer segments disc membrane of photoreceptors and plays a crucial role in the removal of excessive 11-cis and all-trans from discs. Mutations that cause loss of function/mislocalization/misfolding of ABCA4 are thought to lead to a progressive accumulation of cytotoxic bisretinoid compounds and eventually to death of photoreceptors and retinal pigment epithelium cells. Currently, the consequences of most mutations are not known and there is no effective treatment.

 

The c.5461-10T>C mutation in ABCA4 gene was reported to influence ABCA4 transcript processing, resulting in mature transcripts missing exon 39, and exon 39 and 40. Deletion of either or both exons causes a frameshift in the ABCA4 transcript that likely leads to nonsense mediated decay. Splice modulating antisense oligonucleotides (AOs) have been shown to be effective in exon inclusion in other conditions, and we hypothesized that the same strategy may be applicable to STGD1 patients with the c.5461-10T>C mutation.

 

We designed several AOs targeting intronic splicing silencers within intron 39 to enhance inclusion of exon 39 or exon 39 and 40, in the mature ABCA4 transcript. The AOs were transfected into patient fibroblasts carrying the c.5461-10T>C mutation and the ABCA4 transcript was analyzed after 24 hours. An increase in the full-length ABCA4 transcript was observed in treated compared to the untreated cells. This increase is not only through exon 39 inclusion but also prevention of nonsense mediated decay. A decrease in the transcript missing exon 39 was also observed. Further studies to assess ABCA4 protein expression and function after treatment are in progress.

 

This study demonstrates that a splice modulating AO has therapeutic potential for STGD1 patients carrying the c.5461-10T>C mutation through splice correction.

 

  1. Sangermano R, Bax NM, Bauwens MPhotoreceptor et al. Progenitor mRNA Analysis Reveals Exon Skipping Resulting from the ABCA4 c.5461-10T→C Mutation in Stargardt Disease. Ophthalmology. 2016 Jun;123(6):1375-85.
  2. Molday RS. Insights into the Molecular Properties of ABCA4 and Its Role in the Visual Cycle and Stargardt Disease. Prog Mol Biol Transl Sci. 2015;134:415-31.
  3. Aukrust I, Jansson RW, Bredrup C et al. The intronic ABCA4 c.5461-10T>C variant, frequently seen in patients with Stargardt disease, causes splice defects and reduced ABCA4 protein level. Acta Ophthalmol. 2017 May;95(3):240-246.