Abstract
MicroRNAs (miRNAs) are 21-24-nucleotide non-coding RNAs found in diverse organisms. Although hundreds of miRNAs have been cloned or predicted, only very few miRNAs have been functionally characterized. Embryo implantation is a crucial step in mammalian reproduction. Many genes have been shown to be significantly changed in mouse uterus during embryo implantation. However, miRNA expression profiles in the mouse uterus between implantation sites and inter-implantation sites are still unknown. In this study, miRNA microarray was used to examine differential expression of miRNAs in the mouse uterus between implantation sites and inter-implantation sites. Compared with inter-implantation sites, there were 8 up-regulated miR-NAs at implantation sites, which were confirmed by both Northern blot and in situ hybridization. miR-21 was highly expressed in the subluminal stromal cells at implantation sites on day 5 of pregnancy. Because miR-21 was not detected in mouse uterus during pseudopregnancy and under delayed implantation, miR-21 expression at implantation sites was regulated by active blastocysts. Furthermore, we showed that Reck was the target gene of miR-21. Our data suggest that miR-21 may play a key role during embryo implantation.
Highlights
MicroRNAs2 are 21–24-nucleotide non-coding RNAs and found in diverse organisms from plants to humans [5, 6]
Mature miRNAs are incorporated into the RNA inducing silencing complex, and target specific messenger RNAs via imperfect base pairing for translational repression or mRNA cleavage [7]
Confirmation of miRNA Microarray Data at Implantation Sites on Day 5—To confirm results from miRNA microarray, 8 miRNAs from the up-regulated ones were chosen for Northern blot analysis
Summary
MicroRNAs (miRNAs) are 21–24-nucleotide non-coding RNAs and found in diverse organisms from plants to humans [5, 6]. Mature miRNAs are incorporated into the RNA inducing silencing complex, and target specific messenger RNAs via imperfect base pairing for translational repression or mRNA cleavage [7]. Through the analysis of mRNA expression by microarray and SAGE, many genes are shown to be significantly changed in mouse uterus between implantation sites and inter-implantation sites [11, 12]. MiRNA expression profile in the mouse uterus between implantation sites and inter-implantation sites is still unknown. Locked nucleic acid (LNA)-modified capture probes enable high affinity hybridizations and can discriminate between single nucleotide differences in closely related miRNA family members [13]. LNA-modified microarrays were used to distinguish miRNA expression patterns in the mouse uterus at implantation sites in this study. The expression and regulation of target genes of differentially expressed miRNAs were investigated
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