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Soma Dash, Melinda K Brastrom, Diane Slusarski, Salil Lachke; Characterization of a new RNA-binding protein Rbm24 in vertebrate eye development. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1209.
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Recently we described three conserved RNA-binding proteins (RBPs) Tdrd7, Celf1 and Caprin2 that function in vertebrate lens development – findings that serve to indicate the importance of post-transcriptional control of gene expression in ocular cell differentiation. However, the significance of RBPs in early eye development remains unclear. Using the bioinformatics tool iSyTE (integrated Systems Tool for Eye gene discovery) we have identified a new RBP Rbm24 (RNA binding motif protein 24) whose expression is conserved in vertebrate eye development and suggestive of function in this process. In agreement with this prediction, we find that deficiency of Rbm24 in mouse and fish causes eye defects.
Targeted Rbm24 knockout mouse mutants and rbm24a morpholino-knockdown zebrafish morphants were generated and analyzed for eye abnormalities. Immunostaining with eye markers was performed to characterize ocular tissue. RNA immunoprecipitation (RIP) using Rbm24 antibody followed by RT-qPCR on mouse eye tissue was carried out to investigate Rbm24-associated RNA targets. TUNEL assay was performed to examine defects in apoptosis.
Rbm24-/- mice exhibit unilateral anophthalmia (50% penetrance) and microphthalmia (100% penetrance) beginning at embryonic day (E) 11.5. rbm24a-knockdown in zebrafish causes microphthalmia. TUNEL assay suggests that Rbm24-/- mice exhibit apoptosis defects. Interestingly, severe down-regulation of the anophthalmia-linked protein Sox2 was observed in the optic vesicle and the overlying surface ectoderm in Rbm24-/- mice. Further, a second transcription factor involved in early eye development, Lhx2, as well as markers of lens epithelium (E-cad) and fibers (gamma-crystallin) were also found to be down-regulated in Rbm24-/- ocular tissue. RIP assays indicated that Rbm24 binds directly to Sox2 and Lhx2 transcripts in wild-type E14.5 mouse eye tissue, suggesting that Rbm24 mediates direct control of key regulators in the eye.
We have identified a new RBP Rbm24 that functions in early eye development in vertebrates. Rbm24 regulates expression of the transcription factor Sox2, among other important ocular proteins, and its deficiency results in anophthalmia, microphthalmia and lens defects. In light of recent findings on other RBPs, these data suggest that conserved post-transcriptional gene expression regulators have evolved to control eye development in vertebrates.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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