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D.L. Stenkamp, R.A. Frey; Temporally-Selective Induction of Hedgehog Signaling Promotes Photoreceptor Differentiation in Embryonic Zebrafish . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2814.
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Purpose: Hedgehog (Hh) is a secreted signaling protein important for animal development. We have previously shown that Hh signaling from the retinal pigmented epithelium is necessary for complete photoreceptor differentiation in embryonic zebrafish. We wished to determine whether increased Hh signaling is also sufficient to induce precocious or ectopic photoreceptor differentiation. Methods: Fertilized zebrafish eggs were injected with the coding sequence for zebrafish sonic hedgehog (shh), under the control of a heat shock protein promoter (hsp-shh). These embryos, and mock-injected control embryos, were subjected to mild heat shock for one hour at a developmental time early in retinal differentiation. Embryos were analyzed several hours later by in situ hybridization for expression of the shh gene and of rod opsin. Results: Brief heat shock of hsp-shh-injected embryos was successful at inducing ectopic, mosaic expression of shh, including in regions surrounding and within the eye. Similar heat shocks also resulted in prococious expression of rod opsin in regions of the developing retina that do not normally express rod opsin at the developmental time examined. Conclusions: Hh signaling may be sufficient to promote opsin expression in differentiating retina in vivo. We are attempting to develop a transgenic (hsp-shh) zebrafish line for our ongoing studies of the role of Hh signaling in vertebrate retinal development.
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