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Susov Dhakal, Craig Stevens, Omri Weiss, Adi Inbal, Deborah Stenkamp; Role of the Early Ocular Vasculature in Regulation of Retinal Neurogenesis. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5145.
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© ARVO (1962-2015); The Authors (2016-present)
The roles of the early ocular vasculature in regulating the activities of retinal progenitors are not known. We previously reported that in zebrafish cloche (m39) mutants, which lack a cardiovascular system, eyes are reduced in size and display disorganized retinal lamination, reduced rod and cone photoreceptor differentiation, and show disrupted expression of pax6 (Stevens et al., 2012, ARVO abstract #3960). Here we begin to test the alternative hypotheses that a) systemic factors from the circulation and/or b) local factors provided by the ocular vasculature are required for retinal neurogenesis.
The following zebrafish mutants and morphants were used: a) cloche (m39) mutants lack hematopoietic cells, endocardial cells, and endothelial cells; b) VEGF-A morphants were injected with antisense morpholinos targeting VEGF-A as an alternative strategy to prevent development of the vasculature; and c) silent heart (troponin T2a) mutants have a non-contractile heart and lack circulation, but develop blood vessels. These embryos and wild-type sibling controls (or those injected with mismatch morpholino) were examined for the following experimental end points: a) the presence of ocular vasculature; b) eye size; c) retinal lamination; and d) rod and cone photoreceptor differentiation, using histological techniques and indirect immunofluorescence.
Early ocular vasculature does not form in VEGF-A morphants. These embryos show reduced eye size and retinal disorganization, similar that that seen in cloche mutants. In contrast, the silent heart mutants develop ocular vasculature and show a distinct but overlapping retinal phenotype as compared to cloche mutants or VEGF-A morphants. Silent heart mutants have reduced eye size and reduced rod and cone photoreceptor differentiation, but the retinas are properly laminated. In addition we have further characterized the cloche phenotype and have documented reduced retinal cell proliferation and increased cell death as compared to wild-type embryos.
Our results are consistent with a) a specific role for ocular vasculature in the development of a normally laminated neural retina, and b) a role for systemic factors from the circulation in regulating photoreceptor differentiation.
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