Thyroid Hormone Receptor β2 in Regulating Visual Opsin Expression in the Zebrafish Retina
W39
Abstract
Cone photoreceptors in the retina are responsible for color vision. Visual opsin proteins expressed in cones allow for the detection of different wavelengths of light depending on their spectral sensitivity. The mechanisms involved with regulating the expression of each opsin in individual cones are not fully understood. The thyroid hormone receptor trβ2 has been demonstrated to be involved in regulating red opsin expression. Normally trβ2 is expressed in red cones only. We used the transgenic zebrafish crx:trb2 that overexpresses trβ2 in all cones under the cone specific cone-rod homeobox (crx) gene promoter. We evaluated the changes in expression for red (lws1, lws2) sensitive opsins using quantitative PCR on transgenic larvae treated from 2-4 days with thyroid hormone (T3) or DMSO control. In T3 treated transgenic larvae lws2 was downregulated, and lws1 was upregulated. We also evaluated opsin expression in whole eyes from adult transgenics compared to wild type fish. In adult transgenics lws1 and lws2 opsin transcripts were downregulated compared to wild type. Collectively, these results provide further evidence that trβ2 is involved in opsin expression.
Thyroid Hormone Receptor β2 in Regulating Visual Opsin Expression in the Zebrafish Retina
Cone photoreceptors in the retina are responsible for color vision. Visual opsin proteins expressed in cones allow for the detection of different wavelengths of light depending on their spectral sensitivity. The mechanisms involved with regulating the expression of each opsin in individual cones are not fully understood. The thyroid hormone receptor trβ2 has been demonstrated to be involved in regulating red opsin expression. Normally trβ2 is expressed in red cones only. We used the transgenic zebrafish crx:trb2 that overexpresses trβ2 in all cones under the cone specific cone-rod homeobox (crx) gene promoter. We evaluated the changes in expression for red (lws1, lws2) sensitive opsins using quantitative PCR on transgenic larvae treated from 2-4 days with thyroid hormone (T3) or DMSO control. In T3 treated transgenic larvae lws2 was downregulated, and lws1 was upregulated. We also evaluated opsin expression in whole eyes from adult transgenics compared to wild type fish. In adult transgenics lws1 and lws2 opsin transcripts were downregulated compared to wild type. Collectively, these results provide further evidence that trβ2 is involved in opsin expression.