Deficiency of the RNA-binding protein Elavl1 causes changes in the lens transcriptome and leads to cataract

Abstract

Purpose : RNA-binding proteins (RBPs) control the cellular transcriptome and proteome by post-transcriptionally regulating the fate of their target RNAs through mediating splicing, transport, localization, stability and translation. Previous studies have shown that several conserved RBPs Caprin2, Celf1, Rbm24 and Tdrd7 are involved in lens development and its defects and/or cataracts. To further our understanding regarding the function of RBPs in the lens, we applied iSyTE to identify and characterize Elavl1 (ELAV (embryonic lethal, abnormal vision)-like 1; also called HuR (Hu antigen R))’s role in regulating the lens developmental transcriptome.

Methods : Various approaches, namely, RT-PCR, Western Blotting, (WB) and Immunofluorescence were used for validating expression in the lens. Pax6GFPCre was used to drive Elavl1 deletion in the lens in a mouse conditional knockout (Elavl1^cKO) model. Elavl1^cKO lenses were phenotypically characterized by grid imaging and light microscopy. RNA-Sequencing (RNA-seq) was performed on Elavl1^cKO lenses to examine impact on the lens transcriptome.

Results : Elavl1 is expressed in the epithelium and fiber cells in lens embryonic and postnatal development. Elavl1^cKO mice exhibit embryonic-onset fully penetrant lens defects and develop early postnatal cataracts that become severe with age. RNA-seq of Elavl1^cKO lenses identifies among the misexpressed genes, several candidates with known function in the lens that are also associated with lens defects/cataract. Among these are crystallins (Crybb3, Cryga, Crygb, Crygd, Crygn), membrane proteins (Aqp1, Gja1, Slc16a12), RBPs (Caprin2) and autophagy factors (Fyco1). Additionally, RNA-seq identified several new candidates that may be relevant to lens biology, such as the transcription regulatory factor Ell2.

Conclusions : These data demonstrate that the conserved RBP Elavl1 is highly expressed in the lens beginning from embryonic stages of development. Further, Elavl1 deficiency causes fully penetrant embryonic-onset lens defects and early-onset cataract. Transcript profiling identifies several genes–relevant to lens biology–to be misexpressed in the lens upon deletion of Elavl1. This analysis also identifies new candidates with potential function in the lens. Together, these data show that Elavl1 is necessary for proper control of the transcriptome in lens development and perturbation of this process causes cataract.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.