The role of the RNA-binding protein Elavl1 in lens development

Abstract

Purpose : Analogous to DNA-binding proteins called transcription factors (TFs) that bind DNA and mediate transcriptional control, RNA-binding proteins (RBPs) bind RNA and control its post-transcriptional fate, such as splicing, transport, localization, stability and translation into protein. While there are more genes in the human genome that encode RBPs compared to DNA-binding proteins, the former class of proteins are grossly less studied compared to the latter, especially in the context of eye development. To address this knowledge-gap, efforts over the past decade have identified several RBPs (e.g. Caprin2, Celf1, Rbm24, Tdrd7, among others) that are required for proper lens development and whose deficiency causes lens defects and/or cataracts (Lachke (2022) PMID: 34906599). To further advance the role of RBPs in the lens, we used iSyTE to identify Elavl1 (ELAV (embryonic lethal, abnormal vision)-like 1; also called HuR (Hu antigen R) as a high-priority candidate and analyzed its relevance to lens development.

Methods : Elavl1 expression in mouse lens was analyzed by RT-PCR, Western Blotting and immunofluorescence staining (IF). Elavl1 lens-specific conditional knockout (Elavl1^cKO) mice were generated by crossing mice containing Elavl1 floxed alleles and the Pax6GFPCre mouse line. RNA-IP (RIP) using Elavl1 antibody was performed on wild-type post-natal day (P) 15 mouse lens lysates Elavl1.

Results : Using the systems-based tool for eye gene discovery, iSyTE, we predicted Elavl1 to be robustly expressed in the lens. RT-PCR, WB and IF independently validated Elavl1 expression in embryonic and postnatal lens. Further, Elavl1 protein was detected in both anterior epithelium of the lens and fiber cells. Elavl1^cKO mice exhibit microphthalmia and/or lens defects and cataract that progress with age. Initial studies suggest that several lens markers are misexpressed in the Elavl1^cKO lens. Further, RIP assays demonstrate that Elavl1 protein binds Pax6 and Prox1 mRNA in lens cells. These findings suggest that Elavl1 may be involved in post-transcriptionally controling these TFs in the lens.

Conclusions : These data demonstrate that Elavl1 is robustly expressed on both RNA and protein levels in lens development. Elavl1 binds to mRNAs encoding key TFs in the lens and its knockout in mice results in eye and lens defects. Together, these findings indicate that Elavl1 plays an important role the development and maintenance of the lens.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.