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Li He, Polina Lyuboslavsky, Curran Sidhu, Jana T Sellers, P. Michael Iuvone; Characterization of visual function loss in mice with retina-specific disruption of Clock or Arntl genes. Invest. Ophthalmol. Vis. Sci. 2016;57(12):638. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
CLOCK and ARNTL (BMAL1) play critical roles in circadian rhythms in almost all tissues, including retina. In this study we characterized visual function loss and regulation of circadian rhythm genes in mice with retina-specific depletion of CLOCK or BMAL1.
Retina-specific depletion of CLOCK or BMAL1 was achieved using mice with floxed alleles of Clock (rCLOCK) or Arntl (rBMAL1) with CHX10-driven Cre recombinase; floxed mice without Cre were used as controls (WTc; WTb). Contrast sensitivity and ERG amplitudes were measured. Spectral-domain optical coherence tomography (SD-OCT) measurements were taken to measure retinal thickness. Transcript levels were measured by qRT-PCR, and protein expression assessed by immunohistochemistry. ANOVA or unpaired t-test were used for group comparisons; p<0.05 was considered to be statistically significant.
Retina-specific depletion caused a ~96% reduction of Clock mRNA level in rCLOCK mice, and ~84% reduction of Arntl mRNA level in rBMAL1 mice, compared to control mice. rCLOCK mice showed significantly reduced contrast sensitivity, and significantly decreased dark-adapted and light-adapted ERG b wave amplitudes, compared to WTc mice; similar results were found in rBMAL1 vs. WTb mice. A small, but significant reduction of thickness of the neural retina and photoreceptor layer was observed in rCLOCK and rBMAL1 mice compared to their respective controls. In rCLOCK compared with WTc or C57BL/6J mice, mRNA levels of Arntl, Npas2, and Cry1 were significantly up-regulated; and Per1, Per2, Per3, Nr1d1, Dbp, Hlf, and Tef were significantly down-regulated. In rBMAL1 mice compared with WTb or C57BL/6J mice, Npas2 and Cry1 were significantly up-regulated; and Per2, Per3, Nr1d1, Dbp, and Tef were significantly down-regulated. Very few cells expressing CLOCK or BMAL1 protein were observed in either rCLOCK or rBMAL1 mice. Interestingly, disruption of either Clock or Arntl genes alone led to disruption of both CLOCK and BMAL1 proteins, although their mRNA levels were relatively normal.
Retinal-specific depletion of CLOCK or BMAL1 leads to impaired visual function, altered gene expression, structural changes in the retina. Disruption of either Clock or Arntl alone results in loss of both CLOCK and BMAL1 proteins, suggesting that the CLOCK/BMAL1 complex is required for stability of these proteins in the retina.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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