Expression profiles of miRNAs and involvement of miR-100 and miR-34 in regulation of cell cycle arrest in Artemia

Regulation of the cell cycle is complex but critical for proper development, reproduction and stress resistance. To survive unfavourable environmental conditions, the crustacean Artemia produces diapause embryos whose metabolism is maintained at extremely low levels. In the present study, the expression profiles of miRNAs during Artemia diapause entry and termination were characterized using high-throughput sequencing. A total of 13 unclassified miRNAs and 370 miRNAs belonging to 87 families were identified; among them, 107 were differentially expressed during diapause entry and termination. We focused on the roles of two of these miRNAs, miR-100 and miR-34, in regulating cell cycle progression; during the various stages of diapause entry, these miRNAs displayed opposing patterns of expression. A functional analysis revealed that miR-100 and miR-34 regulate the cell cycle during diapause entry by targeting polo-like kinase 1 (PLK1), leading to activation of the mitogen-activated protein kinase kinase-extracellular signal-regulated kinase-ribosomal S6 kinase 2 (MEK-ERK-RSK2) pathway and cyclin K, leading to suppression of RNA polymerase II (RNAP II) activity respectively. The findings presented in the present study provide insights into the functions of miR-100 and miR-34 and suggest that the expression profiles of miRNAs in Artemia can be used to characterize their functions in cell cycle regulation.