The H19 large intergenic non-coding RNA (lincRNA) is one of the most highly abundant and conserved transcripts in mammalian development, being expressed in both embryonic and extra-embryonic cell lineages, yet its physiological function is unknown. Here we show that miR-675, a microRNA (miRNA) embedded in H19's first exon, is expressed exclusively in the placenta from the gestational time point when placental growth normally ceases, and placentas that lack H19 continue to grow. Overexpression of miR-675 in a range of embryonic and extra-embryonic cell lines results in their reduced proliferation; targets of the miRNA are upregulated in the H19 null placenta, including the growth-promoting insulin-like growth factor 1 receptor (Igf1r) gene. Moreover, the excision of miR-675 from H19 is dynamically regulated by the stress-response RNA-binding protein HuR. These results suggest that H19's main physiological role is in limiting growth of the placenta before birth, by regulated processing of miR-675. The controlled release of miR-675 from H19 may also allow rapid inhibition of cell proliferation in response to cellular stress or oncogenic signals.
Bibliographical noteFunding Information:
We thank D. L. Kontoyiannis (Alexander Fleming Biomedical Sciences Research Center, Greece) for supplying HuR−/− MEF cells. We also thank H. Jammes and A. Gabory for assisting with collection of the H19∆3 phenotypic data, J. Webster for preparing samples for mass spectrometry and W. Dean for tissue collections. The authors would also like to thank K. Tabbada, A. Segonds-Pichon and S. Andrews for RNA sequencing, statistical and bioinformatic assistance, respectively. We thank M. Iacovino for creating the A2lox-cre ES cell line. We would also like to thank T. Hore, C. Krueger and J. Houseley for critical reading of the manuscript and all members of the laboratories of W. Reik, M. Hemberger, E. Vigorito and J. Houseley for helpful discussions. This work was supported by BBSRC, the Wellcome Trust, MRC, EU NoE EpiGeneSys, EU BLUEPRINT, NIH/NHLBI (U01HL100407) and the Cambridge Commonwealth Trust.