Deficiency of the conserved RNA-binding protein Elavl1, involved in post-transcriptional gene expression control, causes microphthalmia and cataract, Sandeep Aryal (2b)
From Lauren Mosesso
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The eye is a complex organ made cornea, lens and the retina. The cornea and the lens focus light on to the retina. Defects in coordinated development of these tissues cause birth disorders such as microphthalmia (small eye) or cataract (opacity of the transparent lens). Thus, it is necessary to gain a detailed molecular understanding of eye tissue such as lens development. While the role of DNA-binding proteins classified as “transcription factors” (TFs) is well understood, the role of RNA-binding proteins (RBPs) as regulators of post-transcriptional gene expression is limited. While there are similar numbers (~1500) of TFs and RBPs encoded by the human genome, very few RBPs have been linked to eye/lens defects. To address this knowledge-gap we applied a bioinformatics tool called iSyTE to identify an RBP called Elavl1 (ELAV like RNA-binding protein 1). To validate iSyTE’s prediction, we performed RT-qPCR, immunostaining and Western blotting to demonstrate that Elavl1 is expressed in the developing mouse lens at the level of both RNA and protein. Next to explore the functional significance of Elavl1 expression in the lens, we generated lens-specific Elavl1 conditional knockout mice (Elavl1cKO/cKO) using a lens-specific Pax6GFPCre driver and examined lens development in Elavl1cKO/cKO mice. We find that Elavl1cKO/cKO mice exhibit microphthalmia and cataract early in life at post-natal day 5. Next, we performed RNA-immunoprecipitation that suggests that Elavl1 proteins closely associates with mRNAs for key lens regulatory transcription factors, namely Pax6, Sox2, Prox1 and Maf. Further, we find that Pax6, Sox2, Prox1 and Maf have reduced expression in Elavl1cKO/cKO mouse lenses. Next, by generating and studying a lentiviral-mediated stable Elavl1-knockdown lens epithelial cell line, we demonstrate that Elavl1 post-transcriptionally controls the stability of Pax6 and Sox2 mRNAs. Together, these data identify Elavl1 as a new microphthalmia/cataract-linked RBP that controls the stability of key transcription factors.