Wu CW et al. (2013), Dehydration mediated microRNA response in the A...

XB-ART-47975

Gene 2013 Oct 25;5292:269-75. doi: 10.1016/j.gene.2013.07.064.

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Dehydration mediated microRNA response in the African clawed frog Xenopus laevis.

Wu CW , Biggar KK , Storey KB .

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Exposure to various environmental stresses induces metabolic rate depression in many animal species, an adaptation that conserves energy until the environment is again conducive to normal life. The African clawed frog, Xenopus laevis, is periodically subjected to arid summers in South Africa, and utilizes entry into the hypometabolic state of estivation as a mechanism of long term survival. During estivation, frogs must typically deal with substantial dehydration as their ponds dry out and X. laevis can endure >30% loss of its body water. We hypothesize that microRNAs play a vital role in establishing a reversible hypometabolic state and responding to dehydration stress that is associated with amphibian estivation. The present study analyzes the effects of whole body dehydration on microRNA expression in three tissues of X. laevis. Compared to controls, levels of miR-1, miR-125b, and miR-16-1 decreased to 37±6, 64±8, and 80±4% of control levels during dehydration in liver. By contrast, miR-210, miR-34a and miR-21 were significantly elevated by 3.05±0.45, 2.11±0.08, and 1.36±0.05-fold, respectively, in the liver. In kidney tissue, miR-29b, miR-21, and miR-203 were elevated by 1.40±0.09, 1.31±0.05, and 2.17±0.31-fold, respectively, in response to dehydration whereas miR-203 and miR-34a were elevated in ventral skin by 1.35±0.05 and 1.74±0.12-fold, respectively. Bioinformatic analysis of the differentially expressed microRNAs suggests that these are mainly involved in two processes: (1) expression of solute carrier proteins, and (2) regulation of mitogen-activated protein kinase signaling. This study is the first report that shows a tissue specific mode of microRNA expression during amphibian dehydration, providing evidence for microRNAs as crucial regulators of metabolic depression.

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Species referenced: Xenopus laevis
Genes referenced: mapk1

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	Fig. 1. Xenopus microRNA sequence alignment to human. The microRNA sequences that were not 100% conserved between Xenopus tropicalis and human are shown. Majority of the single nucleotide substitutions are observed at the 3′ end, with perfect homology at the seed regions (underlined) located at the 5′ end.
	Fig. 2. Effect of dehydration on expression of microRNAs in liver of X. laevis. Relative MFI of microRNA expressions after normalization to 5.8 s rRNA. Data are presented as mean ± SEM, for 3–4 independent samples from separate animals. a — indicates significant difference from the corresponding control (P < 0.05).
	Fig. 3. Effect of dehydration on expression of microRNAs in kidney of X. laevis. Relative MFI of microRNA expressions after normalization to 5.8 s rRNA. Data are presented as mean ± SEM, for 3–4 independent samples from separate animals. a — indicates significant difference from the corresponding control (P < 0.05).
	Fig. 4. Effect of dehydration on expression of microRNAs in ventral skin of X. laevis. Relative MFI of microRNA expressions after normalization to 5.8 s rRNA. Data are presented as mean ± SEM, for 3–4 independent samples from separate animals. a — indicates significant difference from the corresponding control (P < 0.05).
	Fig. 5. Co-regulation of microRNAs and putative targeted genes involved in the MAPK signaling pathways. Predicted targets of differentially expressed microRNAs are identified with bolded boxes. All interactions predicting microRNA targeting of regulatory pathways have been predicted using the DIANA-miRPath web server.