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Meaghan Torvund, Aparna Sajja, Victoria P. Connaughton, Fumihito Ono, Takanori Ikenaga, Ralph F. Nelson; Spectral Screen of Isolated Photoreceptor PIII Responses in Zebrafish Retina Uncovers Forward Transgenic with UV Cone Loss. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1183.
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© ARVO (1962-2015); The Authors (2016-present)
To identify rod and cone response abnormalities in zebrafish with transgenic label of retinal neurons.
An enhancer trap screening was performed using the heat shock promoter and eGFP flanked by Tol2 sequences. Larvae resulting from the injected DNA construct were raised to adulthood, and a stable Mendelian line (GE4a) labeling select amacrine, ganglion, and horizontal cells was established. In addition to wild type (TL) lines, Tg(pwl33:GFP) (Luo et al, 2004) and SWS2 (Chinen et al, 2008) lines were crossed with the GE4a fish. SWS1 (Takechi et al, 2003) and Tg(isl2b:gfp)zc7 (Pittman et al, 2008) served as spectral controls. Retinal sections prepared from adult animals were observed by confocal microscopy. PIII spectral data, collected on dark, UV-yellow, blue (418nm), red (627nm), and purple (418 & 627nm) backgrounds from eyecups perfused with MEM (5%CO2, 95%O2) plus 10mM L-Aspartate were modeled (Nelson & Singla, 2009) to generate spectral sensitivity curves and to calculate rod, red, green, blue and UV cone spectral components.
A cross of the UV-cone labeled Tg(pwl33:GFP)+/+ line and the GE4a +/- line yielded transgenic labeling typical of GE4a, but no UV-cones. A cross of the blue-cone labeled SWS2+/- line with GE4a+/- yielded transgenic labeling of both blue cones and neurons typical of GE4a. Comparison of mean GE4a+/- PIII spectral sensitivities with those of the TL background strain revealed a UV cone signal deficit, a shift in red/green cone balance, and increased dark-adapted sensitivity. UV sensitivity in Tg(pwl33:GFP) and SWS2 lines was normal. UV cone signals were present in Tg(isl2b:gfp)zc7 (ganglion cells) and SWS1 (UV cones).
The GE4a line labels subpopulations of amacrine, ganglion, and horizontal cells in zebrafish retina, but in addition there is a loss of UV cones. In other transgenic lines the presence of eGFP in cones or ganglion cells in itself, did not lead to loss of UV cones or their signals. The genetic pathway leading to a genetically dominant deletion of UV cones in GE4a, as well as labeling of selected amacrine, ganglion and horizontal cells, is not known.
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