Zonular defects in loxl1-deficient zebrafish

BACKGROUND To investigate the roles of the lysyl oxidase-like 1 (loxl1) gene in zebrafish eye development and the potency of loxl1 deficiency in mimicking the ocular manifestations of Exfoliation Syndrome (XFS). METHODS CRISPR/Cas9 technology was used to generate a frameshift coding deletion in zebrafish loxl1. Expression profiles and ocular manifestations of the wildtype, heterozygous mutant (loxl1+/- ) and homozygous mutant (loxl1-/- ) zebrafish were analyzed in a range of developmental stages from zebrafish larvae to dissected adult zebrafish eyes. RESULTS The loxl1 deficiency caused zonular bundling disorders in juvenile zebrafish and accumulation of pearl-like particles adhering to the adult zebrafish zonule. The bundles appeared to lack form and were thinner in both loxl1+/- and loxl1-/- zebrafish compared with the wildtype (P < 0.01 for all Bonferroni post-hoc analyses). The zonule of loxl1-/- zebrafish appeared stretched, ragged and torn, with isolated fibers also detected. The particles in loxl1-/- zebrafish were more numerous (counts: 92.33 ± 10.02/100 μm2 vs 58.33 ± 5.03/100 μm2 , P = 0.006), but smaller in size (diameter: 0.21 ± 0.03 μm vs 0.43 ± 0.04 μm, P = 0.002) compared with those in loxl1+/- . Transmission electron microscopy revealed thinning or even loss of elastic lamina in loxl1+/- Bruch's membrane (thickness of elastic lamina: 92.94 ± 18.19 nm in the wildtype vs 35.65 ± 14.76 nm in loxl1+/- , P = 0.003). The breakage of Bruch's membrane was observed in loxl1-/- . CONCLUSIONS The loxl1-/- zebrafish is a promising animal model of XFS zonular pathology. This article is protected by copyright. All rights reserved.