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Ying Zhu, Jinliang Li, Minjuan Bian, Xin Xia, Michael Nahmou, Catalina Sun, Jeffrey L Goldberg, Michael Kapiloff; Nuclear localized HDAC4 increases retinal ganglion cell survival after optic nerve crush injury. Invest. Ophthalmol. Vis. Sci. 2022;63(7):861.
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© ARVO (1962-2015); The Authors (2016-present)
The regulation of retinal ganglion cell (RGC) death and survival in disease is a complex process controlled in part by changes in gene expression, including that regulated by histone deacetylases (HDACs). However, roles of individual HDACs in RGCs remain poorly understood. In this study, we first screened the potential relevance of individual HDACs to RGC death and survival after optic nerve crush injury. Next, we explored the role of class IIa HDAC4 in injured RGCs and further defined underlying molecular mechanisms.
To study the effect of individual HDACs in RGC after injury, small hairpin RNAs for individual HDAC isoenzymes were expressed using adeno-associated virus (AAV). Optic nerve crush (ONC) injury was used to induce severe axon damage and RGC loss 2 weeks after AAV intravitreal injection in mice. Two weeks after ONC, retina flat mounts were stained with the RGC marker RBPMS to quantify RGC survival. A nuclear localized phosphoablative HDAC4 mutant (3SA) and a truncated HDAC4 mutant (NT) containing only the N-terminal fragment of HDAC4 were also studied. Flag-tagged wildtype and mutant HDAC4 expressed using AAV2 were detected in retina by immunohistochemistry (IHC). Signal intensity in nuclear and cytosol were measured using ImageJ to determine HDAC4 intracellular localization. To test whether nuclear HDAC4 preferentially enhances RGC survival, RGC loss was assessed 2 weeks post ONC by flat mount IHC. Cholera toxin b was intravitreally injected 2 days before endpoint to label regenerated axons.
Inhibited expression of no individual HDAC significantly improved RGC survival after crush injury. Instead, the inhibited expression of only HDAC4 significantly decreased RGC survival. Flag-HDAC4 3SA was localized preferentially to the nucleus, whereas wildtype Flag-HDAC4 was mainly cytosolic. Notably, HDAC4 3SA significantly increased RGC survival and promoted axon regeneration 2 weeks after ONC when compared to GFP control. Overexpression of wild type HDAC4 also tended to increase RGC survival after injury, although not reaching statistical difference. In addition, there was greater RGC survival and axon regeneration following HDAC4 NT expression.
Nuclear localized HDAC4 promotes RGC survival after injury. Enhanced HDAC4 nuclear activity might comprise a new therapy for the prevention of vision loss in diseases like optic nerve injury and glaucoma.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
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