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Jiyao Zhu, Judy M Ogilvie; Cell cycle gene reactivation in rd1 mouse retina prior to degeneration. Invest. Ophthalmol. Vis. Sci. 2017;58(8):126.
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© ARVO (1962-2015); The Authors (2016-present)
Our work and others suggest that cell cycle gene reactivation often precedes neurodegeneration. Using RNA-seq in the rd1 mouse retina, we previously reported a pattern of significantly up-regulated genes associated with cell cycle progression as early as P4, well in advance of photoreceptor cell death at P10 (Zhu and Ogilvie, 2016, ARVO#578). Disassembly of the primary cilium is a feature of both cell cycle reentry in mitotic cells and of photoreceptor cell degeneration. The mechanism linking cilia disassembly to either of these events, however, is poorly understood. We hypothesize that early cell cycle gene reactivation and activation of cilia disassembly contribute to photoreceptor cell death in rd1 mouse.
Using RNA seq data from retinal samples harvested from wild type (wt) and rd1 retinas at either P4 or P6, a gene expression heatmap was generated to visualize a subgroup of co-regulated genes involved in cell cycle and ciliogenesis. Quantitative real time PCR (qRT-PCR), Western blot, and immunohistochemistry were used for analysis of gene expression and of protein expression and localization.
Heatmap results confirmed cell cycle genes and ciliogenic genes share a similar expression pattern. Cdc20, a master regulator of the cell cycle and cilia assembly, was confirmed by qRT-PCR to be 7.6-fold up-regulated in rd1 retinas at P4 (p<.002). A number of other genes associated with disregulation of cell cycle and cilia organization were also confirmed to be up-regulated. Western blot and immunohistochemistry confirmed up-regulation of protein expression and protein mislocalization in rd1 photoreceptors.
Our results are consistent with our hypothesis that cell cycle reactivation is tightly coupled with abnormal cilia disassembly and may be an early indicator of photoreceptor cell death in the rd1 retina. Furthermore, this work establishes the rd1 mouse retina as a valuable model to investigate the mechanism(s) coupling cilia resorption to cell cycle regulation.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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