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Kalyan Dulla, Seda Yilmaz-Elis, Jiayi Miao, Iris Schmidt, Iris Schulkens, Hee Lam Chan, Peter S Adamson; Oligonucleotide-based splice correction of the ABCA4 c.5461-10T>C mutation in Stargardt disease type 1. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5315.
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Stargardt disease type 1 (STGD1) is the most common form of inherited macular dystrophy causing progressive impairment of central vision, with onset typically in childhood or young adulthood. STGD1 has an autosomal recessive mode of inheritance associated with disease-causing mutations in the ABCA4 (ATP-binding cassette, subfamily A, member 4) gene, which encodes a transport protein localized in photoreceptor outer segment disk edges. ABCA4 mainly functions to remove potentially toxic retinoids, such as N-retinylidene-phosphatidylethanolamine, which originate from the phototransduction process. Failure of this transport caused by absent or dysfunctional ABCA4, results in accelerated deposition of a major lipofuscin fluorophore, N-retinylidene-N-retinylethanolamine, in the retinal pigment epithelium with subsequent RPE apoptosis and photoreceptor degeneration. ABCA4 c.5461-10T>C is the third most common mutation and causes exclusion of either exon 39 or exon 39 and 40 together in the mRNA, resulting in shifts of the open reading frame and premature stop codons. This study aimed to prevent exon 39 skipping in the ABCA4 gene using antisense oligonucleotides.
Since ABCA4 is almost exclusively expressed in the retina, a mini-gene construct containing ABCA4 exon 39 along with the flanking introns carrying c.5461-10T>C mutation was used to screen for the ability of antisense oligonucleotides to prevent exon skipping. Optic cups derived from ABCA4 c.5461-10T>C patient iPSC are being used for further characterization. Droplet-digital PCR was used to assess ABCA4 transcript quantification.
Across the length of exon 39 (124 bases) and the adjacent introns, 31 splice correcting antisense oligonucleotides were designed and tested in two rounds to identify the best performing oligo. Antisense oligonucleotide treatment led to an increase in the levels of transcripts containing ABCA4 exon 39, resulting in the formation of full length functional ABCA4 protein.
Splice-correcting antisense oligonucleotides represent a promising treatment option for STGD1.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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