Purchase this article with an account.
Robert Mackin, Diana Mitchell, Deborah L Stenkamp; Endocrine regulation of multi-chromatic color vision. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3845.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Human trichromatic color vision requires that the tandemly-duplicated LWS/MWS (long- and medium-wavelength sensitive) cone opsin genes are differentially expressed in subsets of cones. The trans-acting nuclear signaling molecule thyroid hormone (TH) is endogenously involved in differential regulation of the orthologous, tandemly-duplicated lws1/lws2 cone opsin genes in zebrafish embryos (Mackin et al., 2017 IOVS, vol. 58, 124). Here we demonstrate using live imaging and 2D pattern analysis that individual cones switch opsin expression in response to TH. Using gain- and loss-of-function (GOF; LOF) approaches we determined the LWS cone phenotype is plastic in response to TH in post-embryonic zebrafish.
The lws reporter transgenic lws:Pac(H) embryos were treated with 100nM triiodothyronine (T3) or DMSO (control), for 2-4 days post-fertilization (dpf) for pattern analysis or for 4-5 dpf for live imaging. Imaging was by confocal microscopy and nearest neighbor distance pattern analysis was performed using WinDRP. For cone phenotype plasticity studies, there were four treatment groups. Tg(tg:nVenus-2a-nfnB)wp.rt8 transgenics treated with i) DMSO (control) or ii) 10mM metronidazole, 2-3dpf, which ablates the thyroid gland (LOF). iii) LOF transgenics treated with 386nM thyroxine (T4), 26-31dpf (“rescue”). iv) Transgenic controls treated with T4, 26-31dpf (GOF). Lws1 vs. lws2 expression was measured by qPCR at 31dpf.
Colocalization of GFP (lws1) and RFP (lws2) was observed in individual cones approximately 12 hours into T3 treatment. A switch in expression from RFP to GFP was observed after 17 hours. Pattern analysis confirms that new GFP+ cones did not disrupt the LWS cone mosaic. Results of plasticity studies demonstrate that TH LOF resulted in increased lws2 (n=6; p=0.0006) and reduced lws1 (n=6; p=2.2E-25) compared to controls. T4 rescued lws1/lws2 expression (n=7 p=6.71E-07, and 8.01E-25) respectively, compared to LOF. T4 GOF increased lws1 (n=9; p=0.0099) and decreased lws2 (n=9; p=5.9E-29) compared to controls.
Live imaging and pattern analysis demonstrate a switch from lws2 to lws1 opsin in individual cones in response to T3. Rescue studies revealed plasticity in differential expression of lws1 vs. lws2, indicating that expression of these opsins can be manipulated post-embryonically, and point to endogenous roles for the endocrine hormone, TH in regulating multichromatic color vision in the zebrafish.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
This PDF is available to Subscribers Only