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Restoration of functional PAX6 in aniridia patient iPSC-derived ocular tissue models using repurposed nonsense
Dulce Lima Cunha1,2, Hajrah Sarkar1,3, Jonathan Eintracht1
1UCL Institute of Ophthalmology, London, UK.
Abstract:
Congenital aniridia is a rare, pan-ocular disease causing severe sight loss, with only symptomatic intervention offered to patients. Approximately 40% of aniridia patients present with heterozygous nonsense variants in PAX6, resulting in haploinsufficiency. Translational readthrough-inducing drugs (TRIDs) have the ability to weaken the recognition of in-frame premature termination codons (PTCs), permitting full-length protein to be translated. We established induced pluripotent stem cell (iPSC)-derived 3D optic cups and 2D limbal epithelial stem cell (LESC) models from two aniridia patients with prevalent PAX6 nonsense mutations. Both in vitro models show reduced PAX6 protein levels, mimicking the disease. The repurposed TRIDs amlexanox and 2,6-diaminopurine (DAP) and the positive control compounds ataluren and G418 were tested for their efficiency. Amlexanox was identified as the most promising TRID, increasing full-length PAX6 levels in both models and rescuing the disease phenotype through normalization of VSX2 and cell proliferation in the optic cups and reduction of ABCG2 protein and SOX10 expression in LESCs. This study highlights the significance of patient iPSC-derived cells as a new model system for aniridia and proposes amlexanox as a new putative treatment for nonsense-mediated aniridia.
Insights
Congenital aniridia, a severe vision loss disease, is linked to PAX6 gene mutations. Amlexanox, a drug, shows promise in restoring PAX6 protein levels and rescuing disease phenotypes in patient-derived cell models.
Area of Science:
- Ophthalmology
- Genetics
- Stem Cell Biology
Background:
- Congenital aniridia is a rare genetic disorder causing severe vision impairment.
- Haploinsufficiency of the PAX6 gene, due to nonsense mutations, underlies approximately 40% of aniridia cases.
- Current treatments for aniridia are limited to symptomatic interventions.
Purpose of the Study:
- To develop and utilize patient-derived induced pluripotent stem cell (iPSC) models for studying congenital aniridia.
- To investigate the potential of translational readthrough-inducing drugs (TRIDs) in treating aniridia caused by PAX6 nonsense mutations.
- To identify effective TRIDs for restoring functional PAX6 protein levels and ameliorating aniridia phenotypes.
Main Methods:
- Generation of 3D optic cup and 2D limbal epithelial stem cell (LESC) models from aniridia patient iPSCs harboring PAX6 nonsense mutations.
- Assessment of PAX6 protein levels and disease-specific markers in patient-derived cell models.
- Screening of repurposed TRIDs, including amlexanox and 2,6-diaminopurine (DAP), alongside positive controls (ataluren, G418).
Main Results:
- Patient-derived iPSC models accurately recapitulated reduced PAX6 protein levels characteristic of aniridia.
- Amlexanox demonstrated efficacy in increasing full-length PAX6 protein in both optic cup and LESC models.
- Amlexanox treatment rescued aniridia phenotypes, including normalization of VSX2 and cell proliferation in optic cups, and reduced ABCG2 and SOX10 expression in LESCs.
Conclusions:
- Patient-derived iPSC models represent a valuable platform for aniridia research and drug discovery.
- Amlexanox shows significant potential as a therapeutic agent for aniridia caused by PAX6 nonsense mutations.
- This study provides a foundation for developing novel treatments targeting nonsense-mediated aniridia.
