Purchase this article with an account.
D.L. Stenkamp, S.L. Wardwell; Developmental Genetics of the Rod Photoreceptor Lineage in Zebrafish . Invest. Ophthalmol. Vis. Sci. 2004;45(13):5315.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Expression of hedgehog genes in the retinal pigmented epithelium, and activity of the Hedgehog (Hh) signal transduction pathway, are necessary for the differentiation of rod and cone photoreceptors in the developing zebrafish retina. Experimental knockdown of Hh signaling results in reduced opsin expression, as well as failed expression of the transcription factor rx1 in the photoreceptor layer (Stenkamp et al., 2003). Because the rx gene product can regulate photoreceptor gene expression (Kimura et al., 2000), we hypothesize that the effects of Hh signaling on photoreceptor differentiation may be mediated by rx1. The rx1 gene is expressed in cone photoreceptors of the zebrafish (Chuang et al., 1999), but expression in the rod photoreceptor lineage has not been evaluated. The goals of this study were to unambiguously identify the rod lineage of the embryonic zebrafish, and to determine whether rx1 is expressed in this lineage. Methods: In zebrafish, rod neurogenesis continues after other retinal neurons have become post–mitotic, providing an experimental window for selective labeling of the rod lineage with bromodeoxyuridine (BrdU). BrdU was injected into zebrafish embryos, and after various survival times, embryos were fixed, sectioned and doubly–labeled for BrdU and for cell–specific markers. Results: Injected BrdU accumulates in multipotent progenitor cells and their progeny at the retinal margin, and in isolated cells in the inner nuclear layer (INL) and outer nuclear layer (ONL), as well as in radial clusters of cells spanning the INL and ONL. Some of the BrdU positive cells in the ONL were also rod opsin positive, confirming that the BrdU–labeled lineage gave rise to rod photoreceptors. Some of the BrdU positive cells in the INL were also pax6 positive, confirming the earlier findings of Otteson et al. (2001), that a pax6–expressing cell constitutes the apex of the rod lineage. Conclusions:This study verifies that the rod photoreceptor lineage can be identified in the zebrafish embryo and provides a means by which to further characterize the expression pattern of rx1.
This PDF is available to Subscribers Only