A Homozygous Mutation (c.241G > A, p.A81T) in the Calsequestrin-2 Causes Eye Defects in Zebrafish

Variants in several genes have been linked to congenital syndromes involving anophthalmia and microphthalmia; however, the specific genotypes and phenotypes associated with these conditions remain unclear. Calsequestrin 2 (CASQ2) is highly expressed in rodent extraocular muscles, but its role in eye development is unclear. In a previous study, we identified a novel CASQ2 (c.241G > A, p.A81T) mutation, which replaces the alanine residue at amino acid 81 with threonine, in a patient with catecholaminergic polymorphic ventricular tachycardia (CPVT). Here, we investigated its effect on eye development. The impact of the CASQ2 mutation on eye development was studied in zebrafish embryos by overexpressing the mutant gene. RNA sequencing was used to identify changes in gene expression, involving over 22,000 genes. Overexpression of the CASQ2 mutation in zebrafish embryos resulted in significant eye morphology changes, with 27.78% of embryos exhibiting anophthalmia or microphthalmia, compared to none in the control group (P < 0.0001). RNA sequencing revealed 1,240 differentially upregulated and 1158 downregulated genes in the CASQ2 mutant group. Nine genes significantly associated with eye development were identified, along with alterations in the Wnt signaling pathway and enrichment of six pathways: arginine and proline metabolism, apoptosis, lysosomes, biosynthesis of unsaturated fats, phototransduction, and p53 signaling. The novel CASQ2 mutation (c.241G > A, p.A81T) adversely affects eye development in zebrafish embryos, suggesting additional molecular pathways involved in anophthalmia and microphthalmia. This finding will enhance our understanding of the genetic basis of these eye conditions and may inform future research and therapeutic strategies.