Stargardt disease-associated in-frame ABCA4 exon 17 skipping results in significant ABCA4 function

Area of Science:

• Genetics
• Molecular Biology
• Ophthalmology

Background:

• Stargardt disease (STGD1) is linked to mutations in the ABCA4 gene.
• The role of in-frame exon skipping in ABCA4-associated STGD1 is not fully understood.
• Antisense oligonucleotides (AONs) show promise for modulating gene expression in genetic disorders.

Purpose of the Study:

• To investigate the functional impact of skipping exon 17 in the ABCA4 gene.
• To develop AONs capable of inducing exon 17 skipping in ABCA4.
• To assess the therapeutic potential of AON-mediated exon skipping for STGD1.

Main Methods:

• A STGD1 patient with a splice variant (c.2653+1G>A) leading to exon 17 skipping was analyzed.
• In vitro splicing assays using midigenes in HEK293T cells were performed.
• ATPase activity and subcellular localization of the resulting ABCA4 protein variant were assessed.
• AONs were designed and tested for their efficacy in inducing exon 17 skipping in cell lines and retinal organoids.

Main Results:

• The c.2653+1G>A variant confirmed in-frame skipping of ABCA4 exon 17.
• ABCA4 lacking exon 17 (Asp864_Gly885del) retained 58% of normal ATPase activity and was stable.
• The best AON candidate achieved 59% exon 17 skipping in human retinal organoids.

Conclusions:

• Deletion of ABCA4 exon 17 does not abolish protein activity and may not cause severe STGD1 when combined with a null allele.
• AON-mediated exon skipping is a viable strategy to potentially ameliorate the effects of severe ABCA4 variants in STGD1.
• This approach could restore partial ABCA4 function in STGD1 patients.