September 21, 2015;
Intracellular microRNA profiles form in the Xenopus laevis oocyte that may contribute to asymmetric cell division.
Asymmetric distribution of fate determinants within cells is an essential biological strategy to prepare them for asymmetric division. In this work we measure the intracellular distribution of 12 maternal microRNAs (miRNA) along the animal-vegetal axis of the Xenopus laevis oocyte
using qPCR tomography. We find the miRNAs have distinct intracellular profiles that resemble two out of the three profiles we previously observed for mRNAs. Our results suggest that miRNAs in addition to proteins and mRNAs may have asymmetric distribution within the oocyte
and may contribute to asymmetric cell division as cell fate determinants.
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References [+] :
Figure 1. a. Individual intracellular profiles of miR-16c, miR-18b, miR-20b, miR-93a, miR-363-3p and miR-5102-5p predominantly localized in the center of the oocyte with slight asymmetry towards the animal hemisphere. Blue lines indicate oocytes from the first female and green lines indicate oocytes from the second female. b. Individual intracellular profiles of miR-19b, miR-22, miR-25, miR-100, miR-148b, and miR-221 localized in the vegetal hemisphere. Red lines indicate oocytes from the first female and orange lines indicate oocytes from the second female. Y-axis indicates relative quantity and x-axis indicates the section from the animal pole (section A) to vegetal pole (section E).
Figure 2. Intracellular profiles of the miRNAs and the selected reference mRNAs measured using qPCR tomography (maml1- dark blue, gdf1 – dark red, cdx1 - yellow).Y-axis indicates relative quantity and x-axis indicates the section from the animal pole (section A) to vegetal pole (section E). a. Spatial profiles of miR-16c, miR-18b, miR-20b, miR-93a, miR-363-3p and miR-5102-5p (indicated in blue scale), which are predominant in the animal hemisphere like the mRNA maml1 (dark blue). b. Intracellular profiles of miR-19b, miR-22, miR-25, miR-100, miR-148b, and miR-221 (indicated in red scale), which are predominant in the vegetal hemisphere like the mRNA gdf1 (dark red). Also shown is the mRNA cdx1 (yellow), which has an extreme vegetal profile.
Figure 3. Hierarchical clustering(a) and SOM classification (b) of intracellular profiles along the animal-vegetal axis of the Xenopus laevis oocyte. The hierarchical clustering is presented in a dendrogram, where the similarity between miRNAs/mRNAs is indicated by the distance at which they are joined. Both the dendrogram and the SOM clearly separate the miRNA and mRNA profiles into two clusters. miR-16c, miR-18b, miR-20b, miR-93a, miR-363-3p and miR-5102-5p (light blue) cluster with animally localized mRNA maml1 (dark blue), while miR-19b, miR-22, miR-25, miR-100, miR-148b, and miR-221 (light red) cluster with vegetally localized gdf1 (dark red) and cdx1 (yellow) mRNAs.
Figure 4. Sequences of the studied miRNAs and their predicted target mRNAs (animal mRNAs are shown in blue, vegetal mRNAs in red).Target prediction was performed using MicroCosm Targets Version 5 database (http://www.ebi.ac.uk/enright-srv/microcosm/htdocs/targets/v5/). The conservation is indicated by colored bases: red color indicates high evolutionary conservation, while blue color indicates low conservation. A sequence of miR-5102-5p indicated in black and two nucleotides on the 3´ end of miR-363-3p were not found in the database. Yellow boxes indicate miRNA seed sequences (from 2nd to the 8th nucleotide in the 5´ end).
Identification of novel microRNAs in Xenopus laevis metaphase II arrested eggs.