Abstract
Purpose: :
Zebrafish have become increasingly useful as animal models of human visual system disorders owing largely to the ability to perform forward genetic screens and rapidly identify the affected loci. With an interest in lens development and cataractogenesis, four recessive zebrafish lens mutations have been identified and studied. The genes disrupted in these mutants encode laminin γ1 (lamc1), laminin ß1 (lamb1), an RRM–motif containing protein (hi2735A) and a putative E3 ubiquitin ligase (uhrf1).
Methods: :
Histological and transmission electron microscopic characterizations of mutants have been performed throughout embryogenesis. Molecular studies have assayed lens epithelial cell proliferation, apoptosis in the lens and lens fiber differentiation to begin to identify the physiological defects underlying the lens phenotypes in each of these mutants.
Results: :
lamb1 and lamc1 mutants show defects in lens capsule formation and integrity with the lens rupturing from the capsule and becoming ectopically localized in the retinal neuroepithelium. Lens tissue is degraded in these mutants and is ultimately cleared from the retina by 8dpf. In homozygous recessive hi2735A mutants, small, dysgenic lenses are frequently observed; however in some cases, normal sized lenses with anterior opacifications resembling cataracts result. Interestingly, heterozygous hi2735A mutants develop age–related cataracts by 8–months of age suggesting that haploinsufficiency at this locus is sufficient for cataractogenesis. uhrf1 mutants show severe lens malformations with the lens rupturing from the lens capsule and lens fibers extending amorphously throughout the retinal neuroepithelium.
Conclusions: :
Zebrafish lamb1 and lamc1 mutants provide useful models for the study of lens capsule basement membrane formation while hi2735A and uhrf1 mutants are useful models for the study of lens epithelial cell proliferation and lens fiber differentiation.
Keywords: development • cataract • extracellular matrix