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Jia Xie, Kin-Sang Cho, LUCY Wong, Meeta Mistry, John Hutchinson, Liu Yang, Dong Feng Chen; Interplay between Histone Methyltransferases Ezh2 and G9a Regulates Retinal Ganglion Cell Gene Expression during Development. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5179.
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© ARVO (1962-2015); The Authors (2016-present)
Epigenetic modifications play critical roles in mediating the proliferation and differentiation of retinal cells. We showed previously that both histone methyltransferases (HMTases) G9a and Ezh2 are transiently expressed in the retina during the perinatal period and highly enriched in retinal ganglion cells (RGCs). However, selective inactivation of Ezh2 alone does not affect RGC development or function. We therefore investigated whether Ezh2 and G9a work in conjunction to regulate RGC gene expression and maturation.
Mice carrying targeted deletion of Ezh2 and/or G9a (mEzh2-/- , mG9a-/-, mEzh2-/-G9a+/-, and mEzh2-/-G9a-/-) in RGC progenitors driven by Math5-Cre (induces gene deletion in ~50% of RGCs) were generated. H3K27me3 depositions were detected by immunofluorescence staining. RGC counts were carried out in retina flat-mounts of P0 mouse pups. Axon counts were performed by electron microscope images of optic nerve sections taken from P0 mice. RGC functions of mutant mice were assessed by positive scotopic threshold response (pSTR) of electroretinogram. RNA-sequence gene profiling and genome-wide ChIP analysis were employed to purified RGCs of P0 mouse pups to analyze for changes in gene expression and H3K27me3 depositions.
H3K27me3 deposition was significantly decreased in the ganglion cell layer (GCL) of mEzh2-/- compared to wild-type mice. Absence of both Ezh2 and G9a induced further loss of H3K27me3 depositions in RGCs of mEzh2-/-G9a-/- and mEzh2-/-G9a+/- mice, as demonstrated by immunohistochemistry and ChIP-seq. This was correlated with larger numbers of dysregulated genes in mEzh2-/-G9a+/- mice. Accordingly, there were significant losses of RGCs and axons and reduction of pSTR amplitude in mEzh2-/-G9a-/- and mEzh2-/-G9a+/- mice, but not in mEzh2-/- and mG9a-/- mice, as compared to controls.
Our data indicate that an interplay between Ezh2 and G9a mediates H3K27me3 deposition and gene expression in RGCs to determine cell maturation and function during development.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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