Sequential and additive expression of miR-9 precursors control timing of neurogenesis
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MicroRNAs (miRs) have an important role in tuning dynamic gene expression. However, the mechanism by which they are quantitatively controlled is unknown. We show that the amount of mature miR-9, a key regulator of neuronal development, increases during zebrafish neurogenesis in a sharp stepwise manner. We characterize the spatiotemporal profile of seven distinct microRNA primary transcripts (pri-mir)-9s that produce the same mature miR-9 and show that they are sequentially expressed during hindbrain neurogenesis. Expression of late-onset pri-mir-9-1 is added on to, rather than replacing, the expression of early onset pri-mir-9-4 and -9-5 in single cells. CRISPR/Cas9 mutation of the late-onset pri-mir-9-1 prevents the developmental increase of mature miR-9, reduces late neuronal differentiation and fails to downregulate Her6 at late stages. Mathematical modelling shows that an adaptive network containing Her6 is insensitive to linear increases in miR-9 but responds to stepwise increases of miR-9. We suggest that a sharp stepwise increase of mature miR-9 is created by sequential and additive temporal activation of distinct loci. This may be a strategy to overcome adaptation and facilitate a transition of Her6 to a new dynamic regime or steady state.
Soto , X , Burton , J , Manning , C S , Minchington , T , Lea , R , Lee , J , Kursawe , J , Rattray , M & Papalopulu , N 2022 , ' Sequential and additive expression of miR-9 precursors control timing of neurogenesis ' , Development , vol. 149 , no. 19 , dev200474 . https://doi.org/10.1242/dev.200474
Copyright © 2022 Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
DescriptionFunding: This work was supported by a Wellcome Trust Senior Research Fellowship (090868/Z/09/Z) and a Wellcome Trust Investigator Award (224394/Z/21/Z) to N.P. and a Medical Research Council Career Development Award to C.S.M. (MR/V032534/1). J.B. was supported by a Wellcome Trust Four-Year PhD Studentship in Basic Science (219992/Z/19/Z). Open Access funding provided by The University of Manchester.
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