Dauer larva quiescence alters the circuitry of microRNA pathways regulating cell fate progression in C. elegans
Karp, Xantha ; Ambros, Victor R.
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Keywords
Animals
Caenorhabditis elegans
Caenorhabditis elegans Proteins
Carrier Proteins
Cell Lineage
Disorders of Sex Development
Down-Regulation
Gene Expression Regulation, Developmental
Gene Regulatory Networks
Larva
MicroRNAs
Models, Biological
Phenotype
RNA-Induced Silencing Complex
Signal Transduction
Biochemistry
Developmental Biology
Genomics
Molecular Biology
Molecular Genetics
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Abstract
In C. elegans larvae, the execution of stage-specific developmental events is controlled by heterochronic genes, which include those encoding a set of transcription factors and the microRNAs that regulate the timing of their expression. Under adverse environmental conditions, developing larvae enter a stress-resistant, quiescent stage called 'dauer'. Dauer larvae are characterized by the arrest of all progenitor cell lineages at a stage equivalent to the end of the second larval stage (L2). If dauer larvae encounter conditions favorable for resumption of reproductive growth, they recover and complete development normally, indicating that post-dauer larvae possess mechanisms to accommodate an indefinite period of interrupted development. For cells to progress to L3 cell fate, the transcription factor Hunchback-like-1 (HBL-1) must be downregulated. Here, we describe a quiescence-induced shift in the repertoire of microRNAs that regulate HBL-1. During continuous development, HBL-1 downregulation (and consequent cell fate progression) relies chiefly on three let-7 family microRNAs, whereas after quiescence, HBL-1 is downregulated primarily by the lin-4 microRNA in combination with an altered set of let-7 family microRNAs. We propose that this shift in microRNA regulation of HBL-1 expression involves an enhancement of the activity of lin-4 and let-7 microRNAs by miRISC modulatory proteins, including NHL-2 and LIN-46. These results illustrate how the employment of alternative genetic regulatory pathways can provide for the robust progression of progenitor cell fates in the face of temporary developmental quiescence.
Source
Development. 2012 Jun;139(12):2177-86. doi: 10.1242/dev.075986. Link to article on publisher's site