The Role of Apobec2 During Zebrafish Retina and Optic Nerve Regeneration.

摘要

Despite a high degree of similarity in retinal structure and function, zebrafish respond to retina and optic nerve damage with a regenerative response, while mammals do not. Moreover, the cell types responsible for these regenerative events, Muller glia (MG) and retinal ganglion cells (RGCs), are present in both zebrafish and mammalian retinas. The key to stimulating endogenous regeneration in mammals following retina or optic nerve damage likely resides in the ability to coax mammalian MG or RGCs into responding similarly to their zebrafish counterparts. To this end, zebrafish have been used as a model system in an attempt to understand the causative events and the cellular changes occurring in MG and RGCs during regeneration.;This work describes the identification and characterization of Apolipoprotein B mRNA Editing Complex 2a and 2b (Apobec2a,2b) as components of these regenerative events in zebrafish. Although Apobec2 proteins were first identified over 13 years ago, their function has remained unresolved. Other members of the Apobec protein family participate in cytosine deaminase-dependent DNA/RNA mutagenesis and DNA demethylation. The experiments described in this work were designed with the goal of learning about the events accompanying retina and optic nerve regeneration and about the biochemical function of Apobec2 proteins, simultaneously. Herewith, the following is characterized during regeneration: gene expression programs, the regulation of DNA methylation, the poised programming state of quiescent MG, changes in mRNA editing, and the activation of the immune response in the progression of regeneration. Furthermore, we demonstrate that Apobec2a,2b are necessary for zebrafish retina and optic nerve regeneration and that they function independent of DNA demethylation, RNA editing, and likely cytosine deamination. We show that their biochemical function is conserved and dependent on the proper binding of zinc, and we identify Apobec2 interacting proteins and characterize potential roles for these interactions. Finally, a working model is proposed in which Apobec2a,2b function independent of cytosine deamination during retina and optic nerve regeneration. Cumulatively, this work serves as a valuable resource to the current understanding of zebrafish retina and optic nerve regeneration and the biochemical function of Apobec2 proteins, and opens multiple avenues for future research.