Functional characterization of RNA-binding protein IMP2 in primary Glioma cell lines [HTS]

Cancer stem cells (CSC) dictate tumor cell heterogeneity in diverse cancer types and arise, in part, from microRNA (miRNA)-dependent alteration of gene expression. The let-7 miRNA family induces differentiation by silencing genes that maintain stemness and is repressed by the RNA-binding proteins LIN28A/B, which preserve stemness in normal embryonic and malignant cells. Here, we observed that LIN28A/B is undetectable in glioma stem cells (GSC) whereas let-7 and, paradoxically, their target genes are highly expressed. Using photoactivatable-ribonucloside-enchanced crosslinking and immunoprecipitation (PAR-CLIP), we show that insulin-like growth factor-2 mRNA-binding protein 2 (IMP2) protects let-7 target genes from silencing and provides a mechanistically distinct alternative to LIN28A/B toward both GSC and neural stem cell specification. Our observations define the RNA-binding repertoire of IMP2 and identify a mechanism by which it supports GSC maintenance. Overall design: We characterized RNA binding sites of IMP2 in MGG8 Glioma cancer stem cells and differentiated cells. To profile changes upon IMP2 modulation we performed RNA-Seq in MGG4 and 8 cells in both states upon IMP2 knockdown and overexpression. Furthermore we investigated changes during differentiation from cancer stem cells to adherent cells in 6 and 7 RNA-Seq datasets in MGG4 and 8 cells.