Lin28a regulates neuronal differentiation and controls miR-9 production

Jakub S Nowak,Flavia De Lima Alves,Gracjan Michlewski,Nila Roy Choudhury,Juri Rappsilber

doi:10.1038/ncomms4687

Abstract

microRNAs shape the identity and function of cells by regulating gene expression. It is known that brain-specific miR-9 is controlled transcriptionally; however, it is unknown whether post-transcriptional processes contribute to establishing its levels. Here, we show that miR-9 is regulated transcriptionally and post-transcriptionally during neuronal differentiation of the embryonic carcinoma cell line P19. We demonstrate that miR-9 is more efficiently processed in differentiated than undifferentiated cells. We reveal that Lin28a affects miR-9 by inducing the degradation of its precursor through a uridylation-independent mechanism. Furthermore, we show that constitutively expressed untagged but not GFP-tagged Lin28a decreases differentiation capacity of P19 cells, which coincides with reduced miR-9 levels. Finally, using an inducible system we demonstrate that Lin28a can also reduce miR-9 levels in differentiated P19 cells. Together, our results shed light on the role of Lin28a in neuronal differentiation and increase our understanding of the mechanisms regulating the level of brain-specific microRNAs.

Highlights

MicroRNAs shape the identity and function of cells by regulating gene expression
We demonstrate that Lin28a, a protein previously implicated in the regulation of let-7 biogenesis, binds to the miR-9 precursor and decreases the cellular levels of miR-9 during retinoic acid (RA)-mediated P19 cell neuronal differentiation
To determine whether post-transcriptional regulation of brain-specific miR-9 contributes to establishing its intercellular concentrations, we analysed the level of mature and corresponding primary transcripts at different stages of P19 cell neuronal differentiation

Summary

Introduction

MicroRNAs shape the identity and function of cells by regulating gene expression. It is known that brain-specific miR-9 is controlled transcriptionally; it is unknown whether posttranscriptional processes contribute to establishing its levels. Our results shed light on the role of Lin28a in neuronal differentiation and increase our understanding of the mechanisms regulating the level of brain-specific microRNAs. Small (21–22 nucleotide) RNAs called microRNAs (miRs) have emerged as vital regulators of the post-transcriptional control of gene expression[1]. We have demonstrated that the brain-enriched expression of miR-7, which is processed from a ubiquitous primary transcript, is supported by inhibition of its biogenesis in non-neural cells[28]. We demonstrate that Lin28a, a protein previously implicated in the regulation of let-7 biogenesis, binds to the miR-9 precursor and decreases the cellular levels of miR-9 during retinoic acid (RA)-mediated P19 cell neuronal differentiation. Our results provide the basis for better understanding the mechanism regulating the levels of brainspecific miRs and their control of neuronal differentiation

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Conclusion