Thyroid Hormone Control of Long Wavelength-Sensitive (lws1) Cone Opsin Expression May be Reversible
Faculty Mentor Information
Dr. Deborah Stenkamp, University of Idaho; and Adedamola Oyekunle, University of Idaho
Presentation Date
7-16-2026
Abstract
Vertebrate color vision relies upon cone photoreceptor subtypes expressing distinct opsins. Thyroid hormone (TH) regulates differential expression of tandemly-duplicated long-wavelength-sensitive (lws) cone opsin genes in zebrafish, with exogenous TH promoting upregulation of lws1 while downregulating lws2. We tested the hypothesis that this “opsin switching” can operate in reverse, by experimentally withdrawing TH following acute exposure in zebrafish embryos/larvae. Embryo clutchmates were assigned to three groups: DMSO vehicle control (“CON”), short TH treatment+withdrawal (“TH/Wash”), and prolonged TH treatment (“TH/TH”). TH/TH elevated lws1 expression (RT-qPCR) relative to CON (p < 0.0001) and TH/Wash (p < 0.01), consistent with our prior reports. Interestingly, no difference in lws1 expression was detected between CON and TH/Wash (p=0.1042), suggesting that lws1 upregulation did not persist after hormone removal. For lws2, both TH/Wash (p=0.0065) and TH/TH (p < 0.0001) showed reduced expression compared to CON. Confocal imaging of lws:PAC(H) [lws1:GFP;lws2:RFP] transgenic zebrafish revealed co-expression of GFP and RFP within individual cones of TH/Wash, suggesting that LWS cones expressed both opsins. These findings support one component of our hypothesis in that lws1 levels in TH/Wash matched those of CON. These results extend our understanding of TH-regulated opsin switching as a dynamic, time-dependent process in the developing zebrafish retina.
Thyroid Hormone Control of Long Wavelength-Sensitive (lws1) Cone Opsin Expression May be Reversible
Vertebrate color vision relies upon cone photoreceptor subtypes expressing distinct opsins. Thyroid hormone (TH) regulates differential expression of tandemly-duplicated long-wavelength-sensitive (lws) cone opsin genes in zebrafish, with exogenous TH promoting upregulation of lws1 while downregulating lws2. We tested the hypothesis that this “opsin switching” can operate in reverse, by experimentally withdrawing TH following acute exposure in zebrafish embryos/larvae. Embryo clutchmates were assigned to three groups: DMSO vehicle control (“CON”), short TH treatment+withdrawal (“TH/Wash”), and prolonged TH treatment (“TH/TH”). TH/TH elevated lws1 expression (RT-qPCR) relative to CON (p < 0.0001) and TH/Wash (p < 0.01), consistent with our prior reports. Interestingly, no difference in lws1 expression was detected between CON and TH/Wash (p=0.1042), suggesting that lws1 upregulation did not persist after hormone removal. For lws2, both TH/Wash (p=0.0065) and TH/TH (p < 0.0001) showed reduced expression compared to CON. Confocal imaging of lws:PAC(H) [lws1:GFP;lws2:RFP] transgenic zebrafish revealed co-expression of GFP and RFP within individual cones of TH/Wash, suggesting that LWS cones expressed both opsins. These findings support one component of our hypothesis in that lws1 levels in TH/Wash matched those of CON. These results extend our understanding of TH-regulated opsin switching as a dynamic, time-dependent process in the developing zebrafish retina.