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Craig B. Stevens, Seth Adamson, Deborah L. Stenkamp; Retinal Abnormalities in a Zebrafish Mutant Lacking Retinal and Hyaloid Vasculature. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3960.
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Human retinal disorders are often associated with cardiovascular abnormalities or risk profiles. Interestingly, many genetic and pharmacological zebrafish models for retinal dysgenesis also display cardiovascular defects, raising questions about the role of the embryonic vascular supply to the eye in supporting or regulating retinal development. In the present study, we examine embryonic retinal development in cloche mutant zebrafish embryos, which fail to develop hematopoietic, endothelial and endocardial cells. We test the hypotheses that the cloche locus is required for embryonic development of the hyaloid and retinal vasculature, as well as for that of the neural retina.
Eyes, retinas, and retinal and hyaloid vasculature of cloche (m39) mutants and their wild-type siblings were examined using histological techniques, in situ hybridization, and morphometric methods. Some embryos were treated with retinoic acid (RA) in rescue experiments.
Cloche mutants failed to develop hyaloid and retinal vasculature. As compared to their wild-type siblings, cloche mutants became microphthalmic and displayed significant defects in histology of the neural retina and in rod and cone photoreceptor cell differentiation. Defects in rod, but not cone differentiation were partially rescued by RA treatment. A search for possible causes of retinal differentiation defects revealed that retinal transcription factors essential for retinal development were expressed in cloche mutants, although the patterns of expression of NeuroD and pax6 were abnormal. Expression of Hsp27, a marker of cell stress, was observed in embryonic cloche retinas but not in wild-type siblings.
The cloche locus is essential for normal retinal development, and for development of the hyaloid and retinal vasculature. Defects in rod development related to the absence of cloche function can be partially rescued by RA treatment. One explanation for these results is that early hyaloid and retinal vasculature provides factors required for normal retinal development. Alternatively, genes altered by the genomic deletion in cloche, may play specific, novel, roles in retinal development. Blastomere transplant experiments are underway to test for tissue-autonomous vs. non tissue-autonomous roles of the cloche locus.
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