Abstract
The cell-context dependency for RNA binding proteins (RBPs) mediated control of stem cell fate remains to be defined. Here we adapt the HyperTRIBE method using an RBP fused to a Drosophila RNA editing enzyme (ADAR) to globally map the mRNA targets of the RBP MSI2 in mammalian adult normal and malignant stem cells. We reveal a unique MUSASHI-2 (MSI2) mRNA binding network in hematopoietic stem cells that changes during transition to multipotent progenitors. Additionally, we discover a significant increase in RNA binding activity of MSI2 in leukemic stem cells compared with normal hematopoietic stem and progenitor cells, resulting in selective regulation of MSI2’s oncogenic targets. This provides a basis for MSI2 increased dependency in leukemia cells compared to normal cells. Moreover, our study provides a way to measure RBP function in rare cells and suggests that RBPs can achieve differential binding activity during cell state transition independent of gene expression.
Highlights
The cell-context dependency for RNA binding proteins (RBPs) mediated control of stem cell fate remains to be defined
Overexpression of MSI2-ADA in the human AML cell line MOLM-13 resulted in a significant increase in the number of A->G editing events and edit frequency on RNAs compared with the empty vector control (MIG) (Fig. 1b, c)
We found that hematopoietic stem cells (HSCs) targets are highly enriched for stem cell programs, such as HSCs, myelodysplasia syndrome (MDS) and leukemia stem cells (LSCs); whereas multipotent progenitors (MPPs) targets are enriched for lineage-specific programs, such as macrophages, T cells and B cells (Fig. 2f, Supplementary Fig. 5b, Supplementary Data 3)
Summary
The cell-context dependency for RNA binding proteins (RBPs) mediated control of stem cell fate remains to be defined. MSI2 targets were identified in two independent AML cell lines (NB4 and K562) using CLIP methods[19,21] These strategies characterized a handful of validated direct MSI2 mRNA targets, they did not provide a comprehensive map of endogenous targets in stem cells nor address cell-type specific binding activity of MSI2. While Msi[2] knockout mice exhibit a modest reduction in blood cells and about 50% reduction in hematopoietic stem and progenitor cells (HSPCs), depletion of MSI2 severely reduced the frequency and activity of LSCs in both mouse and human systems This indicates a significantly higher dependency and requirement for MSI2 in LSCs and development of leukemia[20,22,23,24,25,26]. The cause for this differential requirement for MSI2 function in LSCs and HSCs is not known
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
