title: Let-7b/c enhance the stability of a tissue-specific mRNA during mammalian organogenesis as part of a feedback loop involving KSRP.
abstract: Gene silencing mediated by either microRNAs (miRNAs) or Adenylate/uridylate-rich elements Mediated mRNA Degradation (AMD) is a powerful way to post-transcriptionally modulate gene expression. We and others have reported that the RNA-binding protein KSRP favors the biogenesis of select miRNAs (including let-7 family) and activates AMD promoting the decay of inherently labile mRNAs. Different layers of interplay between miRNA- and AMD-mediated gene silencing have been proposed in cultured cells, but the relationship between the two pathways in living organisms is still elusive. We conditionally deleted Dicer in mouse pituitary from embryonic day (E) 9.5 through Cre-mediated recombination. In situ hybridization, immunohistochemistry, and quantitative reverse transcriptase-PCR revealed that Dicer is essential for pituitary morphogenesis and correct expression of hormones. Strikingly, αGSU (alpha glycoprotein subunit, common to three pituitary hormones) was absent in Dicer-deleted pituitaries. αGSU mRNA is unstable and its half-life increases during pituitary development. A transcriptome-wide analysis of microdissected E12.5 pituitaries revealed a significant increment of KSRP expression in conditional Dicer-deleted mice. We found that KSRP directly binds to αGSU mRNA, promoting its rapid decay; and, during pituitary development, αGSU expression displays an inverse temporal relationship to KSRP. Further, let-7b/c downregulated KSRP expression, promoting the degradation of its mRNA by directly binding to the 3'UTR. Therefore, we propose a model in which let-7b/c and KSRP operate within a negative feedback loop. Starting from E12.5, KSRP induces the maturation of let-7b/c that, in turn, post-transcriptionally downregulates the expression of KSRP itself. This event leads to stabilization of αGSU mRNA, which ultimately enhances the steady-state expression levels. We have identified a post-transcriptional regulatory network active during mouse pituitary development in which the expression of the hormone αGSU is increased by let7b/c through downregulation of KSRP. Our study unveils a functional crosstalk between miRNA- and AMD-dependent gene regulation during mammalian organogenesis events.
authors: INSERM U1065, Centre Méditerranéen de Médecine Moléculaire (C3M), Team 10-Control of Gene Expression, Nice, France.
authors: Emanuela
authors: E
authors: Repetto
authors: Paola
authors: P
authors: Briata
authors: Nathalie
authors: N
authors: Kuziner
authors: Brian D
authors: BD
authors: Harfe
authors: Michael T
authors: MT
authors: McManus
authors: Roberto
authors: R
authors: Gherzi
authors: Michael G
authors: MG
authors: Rosenfeld
authors: Michele
authors: M
authors: Trabucchi
mesh_terms: D000818:Animals; D053487:DEAD-box RNA Helicases / Q000235:genetics; D047108:Embryonic Development / Q000235:genetics; D025461:Feedback, Physiological; D018507:Gene Expression Regulation, Developmental; D015292:Glycoprotein Hormones, alpha Subunit / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D035683:MicroRNAs / Q000235:genetics* / Q000378:metabolism; D041681:NIH 3T3 Cells; D038081:Organogenesis / Q000235:genetics*; D010902:Pituitary Gland / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D010907:Pituitary Hormones / Q000235:genetics / Q000378:metabolism; D020871:RNA Stability / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D043244:Ribonuclease III / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism
chemical_list: D015292:Glycoprotein Hormones, alpha Subunit; C507913:Khsrp protein, mouse; D035683:MicroRNAs; D010907:Pituitary Hormones; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D015534:Trans-Activators; C542687:mirnlet7 microRNA, mouse; C509781:Dicer1 protein, mouse; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases