Purchase this article with an account.
Logan Ganzen, Chi Pui Pang, Mingzhi Zhang, Motokazu Tsujikawa, Yuk Fai Leung; Visual Motor Response of a Transgenic Retinitis Pigmentosa Zebrafish Model. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5869.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Retinitis Pigmentosa (RP) affects approximately 1 in 4000 individuals globally, and there are currently no effective treatment options available. To identify new drugs, we optimized a visual-behaviour assay, termed visual-motor response (VMR) (Emran et al., 2008), around a transgenic zebrafish carrying a truncated human rhodopsin transgene (Tg(rho:Hsa.RH1_Q344X)). This line also carried a Tg(-3.7rho:EGFP) reporter for rod visualization. The Q344X larvae experiences significant rod degeneration by 7 days post-fertilization (dpf) (Nakao et al., 2012).
To assess the vision of the Q344X zebrafish, the VMR assay was run under a dim-light condition based on recorded rod b-waves in larval fish (Moyano et al., 2013) and the minimum cone activation threshold in mice (Cachafeiro et al., 2010). Specifically, Q344X and control larvae at 7dpf were placed into a 96-well plate and acclimated to a dim-light source (1.802e-05 μW/cm2 at 500nm) for 1 hour. The VMR was tracked and quantified during light offset. The total distance travelled was averaged and analyzed at one second post-stimulus. Retinas were dissected from Q344X and control larvae and whole-mounted to validate the rod degeneration in the Q344X model.
We found that the Q344X larvae displayed an attenuated VMR (0.121 ± 0.041cm) to the dim-light offset as compared to the control larvae (0.2751 ± 0.038cm). (Two-Sample T-test; p-value=4.619e-14, N=19). Analysis of whole-mounted retinae indicated significant rod degeneration at 7dpf compared with controls (Control: 87 rods/retina, Q344X: 9.3 rods/retina, Welch's Two-Sample T-test p-value=1.4e4,). It is unlikely that the cones of the zebrafish contributed to this VMR since the light intensity of the assay was below the cone detection threshold of mice. As the only apparent difference between the two groups of larvae is significant rod degeneration, it can be concluded that the behavioral phenotype was a result of the degeneration.
These results suggest that the attenuated Q344X VMR is a result of the rod degeneration. This behavioral phenotype can be utilized to screen chemical libraries to identify compounds that ameliorate the rod degeneration. Compounds that prevent degeneration are expected to result in a significant increase in VMR in response to the dim-light stimulus.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
This PDF is available to Subscribers Only