Generation of human induced pluripotent stem cell lines from a subject with UBAP1L-associated retinal dystrophy and CRISPR/cas9-corrected isogenic iPSC lines.

A Human induced pluripotent stem cell (iPSC) line was generated from dermal fibroblasts of a patient affected with an autosomal recessive retinal dystrophy carrying the homozygous c.910-7G>A variant in UBAP1L. Three isogenic control iPSC lines derived from this affected subject line were created using CRISPR/Cas9 engineering. All iPSC lines expressing the pluripotency markers, were able to differentiate into the three germ layers, and exhibit a normal karyotype. These cellular models will provide a powerful tool to study disease mechanisms associated with the recently reported UBAP1L- associated retinal dystrophy and better understand the role of the protein in retinal physiology.

Variants in UBAP1L lead to autosomal recessive rod-cone and cone-rod dystrophy.

PURPOSE: Progressive inherited retinal degenerations (IRDs) affecting rods and cones are clinically and genetically heterogeneous and can lead to blindness with limited therapeutic options. The major gene defects have been identified in subjects of European and Asian descent with only few reports of North African descent. METHODS: Genome, targeted next-generation, and Sanger sequencing was applied to cohort of ∼4000 IRDs cases. Expression analyses were performed including Chip-seq database analyses, on human-derived retinal organoids (ROs), retinal pigment epithelium cells, and zebrafish. Variants' pathogenicity was accessed using 3D-modeling and/or ROs. RESULTS: Here, we identified a novel gene defect with three distinct pathogenic variants in UBAP1L in 4 independent autosomal recessive IRD cases from Tunisia. UBAP1L is expressed in the retinal pigment epithelium and retina, specifically in rods and cones, in line with the phenotype. It encodes Ubiquitin-associated protein 1-like, containing a solenoid of overlapping ubiquitin-associated domain, predicted to interact with ubiquitin. In silico and in vitro studies, including 3D-modeling and ROs revealed that the solenoid of overlapping ubiquitin-associated domain is truncated and thus ubiquitin binding most likely abolished secondary to all variants identified herein. CONCLUSION: Biallelic UBAP1L variants are a novel cause of IRDs, most likely enriched in the North African population.