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Article
A feedback circuit involving let-7-family miRNAs and DAF-12 integrates environmental signals and developmental timing in Caenorhabditis elegans
Proceedings of the National Academy of Sciences of the United States of America (2009)
  • Christopher M. Hammell, University of Massachusetts Medical School
  • Xantha Karp, University of Massachusetts Medical School
  • Victor R. Ambros, University of Massachusetts Medical School
Abstract
Animal development is remarkably robust; cell fates are specified with spatial and temporal precision despite physiological and environmental contingencies. Favorable conditions cause Caenorhabditis elegans to develop rapidly through four larval stages (L1-L4) to the reproductive adult. In unfavorable conditions, L2 larvae can enter the developmentally quiescent, stress-resistant dauer larva stage, enabling them to survive for prolonged periods before completing development. A specific progression of cell division and differentiation events occurs with fidelity during the larval stages, regardless of whether an animal undergoes continuous or dauer-interrupted development. The temporal patterning of developmental events is controlled by the heterochronic genes, whose products include microRNAs (miRNAs) and regulatory proteins. One of these proteins, the DAF-12 nuclear hormone receptor, modulates the transcription of certain let-7-family miRNAs, and also mediates the choice between the continuous vs. dauer-interrupted life history. Here, we report a complex feedback loop between DAF-12 and the let-7-family miRNAs involving both the repression of DAF-12 by let-7-family miRNAs and the ligand-modulated transcriptional activation and repression of the let-7-Fam miRNAs by DAF-12. We propose that this feedback loop functions to ensure robustness of cell fate decisions and to coordinate cell fate with developmental arrest.
Publication Date
November 3, 2009
Publisher Statement

Citation: Hammell CM, Karp X, Ambros V. A feedback circuit involving let-7-family miRNAs and DAF-12 integrates environmental signals and developmental timing in Caenorhabditis elegans. Proc Natl Acad Sci U S A. 2009 Nov 3;106(44):18668-73. doi: 10.1073/pnas.0908131106. Epub 2009 Oct 14. PubMed PMID: 19828440; PubMed Central PMCID: PMC2774035.

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Citation Information
Christopher M. Hammell, Xantha Karp and Victor R. Ambros. "A feedback circuit involving let-7-family miRNAs and DAF-12 integrates environmental signals and developmental timing in Caenorhabditis elegans" Proceedings of the National Academy of Sciences of the United States of America Vol. 106 Iss. 44 (2009)
Available at: http://works.bepress.com/victor_ambros/3/