The let-7 microRNA Directs Vulval Development through a Single Target

MicroRNAs (miRNAs) play essential, conserved roles in diverse developmental processes through association with the miRNA-induced silencing complex (miRISC). Whereas fundamental insights into the mechanistic framework of miRNA biogenesis and target gene silencing have been established, posttranslational modifications that affect miRISC function are less well understood. Here we report that the conserved serine/threonine kinase, casein kinase II (CK2), promotes miRISC function in Caenorhabditis elegans. CK2 inactivation results in developmental defects that phenocopy loss of miRISC cofactors and enhances the loss of miRNA function in diverse cellular contexts. Whereas CK2 is dispensable for miRNA biogenesis and the stability of miRISC cofactors, it is required for efficient miRISC target mRNA binding and silencing. Importantly, we identify the conserved DEAD-box RNA helicase, CGH-1/DDX6, as a key CK2 substrate within miRISC and demonstrate phosphorylation of a conserved N-terminal serine is required for CGH-1 function in the miRNA pathway.

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“…Rup phenotypes of let-7 family mutants can be partially suppressed by concurrent depletion of their mRNA targets (35,41).…”

Section: Resultsmentioning

confidence: 99%

Casein kinase II promotes target silencing by miRISC through direct phosphorylation of the DEAD-box RNA helicase CGH-1

Alessi

Khivansara

Han

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…2M). Consistent with the expressions of all the miRNAs in the vulva, let-7 mutants and mir-48 mir-241; mir-84 triple mutants show a phenotype of bursting through the vulva (Reinhart et al 2000;Abbott et al 2005), and the activity of let-7 miRNA is cell-autonomously required to rescue the bursting phenotype in let-7 mutants (Ecsedi et al 2015).…”

Section: Resultsmentioning

confidence: 67%

A whole-mount in situ hybridization method for microRNA detection in Caenorhabditis elegans

Andachi

Kohara

2016

RNA

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Whole-mount in situ hybridization (WISH) is an outstanding method to decipher the spatiotemporal expression patterns of microRNAs (miRNAs) and provides important clues for elucidating their functions. The first WISH method for miRNA detection was developed in zebrafish. Although this method was quickly adapted for other vertebrates and fruit flies, WISH analysis has not been successfully used to detect miRNAs in Caenorhabditis elegans. Here, we show a novel WISH method for miRNA detection in C. elegans. Using this method, mir-1 miRNA was detected in the body-wall muscle where the expression and roles of mir-1 miRNA have been previously elucidated. Application of the method to let-7 family miRNAs, let-7, mir-48, mir-84, and mir-241, revealed their distinct but partially overlapping expression patterns, indicating that miRNAs sharing a short common sequence were distinguishably detected. In pash-1 mutants that were depleted of mature miRNAs, signals of mir-48 miRNA were greatly reduced, suggesting that mature miRNAs were detected by the method. These results demonstrate the validity of WISH to detect mature miRNAs in C. elegans.

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“…An extreme example may be mir-430, which in zebrafish contains 72 members, consistent with its ability to target a large number of maternal mRNAs (Giraldez et al, 2006). However, other very abundant miRNAs might have a stronger impact on one or a few targets: for example, a recent study in C. elegans showed that the very abundant let-7 exerts its main function through a single target, lin-41 (Ecsedi et al, 2015).…”

Section: Discussionmentioning

confidence: 99%

A framework for understanding the roles of miRNAs in animal development

2017

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MicroRNAs (miRNAs) contribute to the progressive changes in gene expression that occur during development. The combined loss of all miRNAs results in embryonic lethality in all animals analyzed, illustrating the crucial role that miRNAs play collectively. However, although the loss of some individual miRNAs also results in severe developmental defects, the roles of many other miRNAs have been challenging to uncover. This has been mostly attributed to their proposed function as tuners of gene expression or providers of robustness. Here, we present a view of miRNAs in the context of development as a hierarchical and canalized series of gene regulatory networks. In this scheme, only a fraction of embryonic miRNAs act at the top of this hierarchy, with their loss resulting in broad developmental defects, whereas most other miRNAs are expressed with high cellular specificity and play roles at the periphery of development, affecting the terminal features of specialized cells. This view could help to shed new light on our understanding of miRNA function in development, disease and evolution.

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The let-7 microRNA Directs Vulval Development through a Single Target

Cited by 129 publications

References 37 publications

Casein kinase II promotes target silencing by miRISC through direct phosphorylation of the DEAD-box RNA helicase CGH-1

Casein kinase II promotes target silencing by miRISC through direct phosphorylation of the DEAD-box RNA helicase CGH-1

A whole-mount in situ hybridization method for microRNA detection in Caenorhabditis elegans

A framework for understanding the roles of miRNAs in animal development

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