Poster abstracts
Poster number 96 submitted by Jeff Medley
Regulation of miRNA Strand Selection in Caenorhabditis elegans
Jeff Medley (Division of Biology, Kansas State University), Ganesh Panzade (Frederick National Laboratory for Cancer Research; Division of Biology, Kansas State University), Sumire Kurosu (Division of Biology, Kansas State University), Joel Sydzyik, Sarah Coffey, (Division of Biology, Kansas State University), Mira Bhandari (Division of Biology, Kansas State University), Anna Zinovyeva (Division of Biology, Kansas State University)
Abstract:
Gene expression must be tightly regulated to maintain cellular homeostasis and ensure proper animal development. miRNAs are key regulators of gene expression, which typically repress mRNA targets based on sequence complementarity. A critical step in miRNA-mediated gene regulation is the processing of miRNA precursors into duplexes that comprise two strands. One dominant (guide) strand is loaded into an Argonaute to gain functionality, while the other (passenger) strand is degraded. As each miRNA strand would have different mRNA targets, the decision of which strand is loaded into Argonaute effectively determines what genes are subjected to miRNA-mediated repression. Although previous studies have indicated that 5’ nucleotide identity and thermodynamic asymmetry of miRNA duplexes is sufficient to explain strand selection in vitro, it remains unclear whether those sequence cues play a role in determining strand selection in vivo. Here, we used CRISPR/Cas9 genome editing to mutate C. elegans miRNA loci to explore how specific miRNA sequence features impact stand selection in vivo. We found that 5’ nucleotide or thermodynamic asymmetry can largely explain the directionality of miRNA strand selection, although our results suggest additional factors fine tune the levels of each miRNA strand. We found that mutating 5’ nucleotide or thermodynamic asymmetry had different effects on the strand selection of individual miRNAs. For example, mutating the 5’ nucleotide of the guide strand to an unfavorable nucleotide was sufficient to reverse strand selection of miR-1 and miR-2 but not miR-58. In some cases we observed development-dependent differences in the relative abundances of miRNA strands, supporting that sequence-independent factors may regulate miRNA strand selection in vivo. Our results suggest that changes in miRNA strand selection are unlikely to be due to altered miRNA processing and are more likely to impact strand selection at the miRNA duplex level. Collectively our findings provide important insights into how miRNA strand selection is specified and regulated in vivo.
Keywords: miRNA, Strand Selection, C elegans