MicroRNAs (miRNAs) constitute a class of noncoding RNAs that post‐transcriptionally regulate gene expression. Recent evidence indicates that many miRNAs function as oncogenes or tumor suppressors by negatively regulating their target genes. In our previous study, using miRNA microarray analysis, we found that miRNA‐182 (miR‐182) was significantly downregulated in human gastric adenocarcinoma tissue samples. Here, we confirmed the downregulation of miR‐182 in a larger sample of gastric tissue samples. Overexpression of miR‐182 suppressed the proliferation and colony formation of gastric cancer cells. An oncogene, encoding cAMP‐responsive element binding protein 1 (CREB1), serves as a direct target gene of miR‐182. A fluorescent reporter assay confirmed that miR‐182 binds specifically to the predicted site of the CREB1 mRNA 3′‐UTR. When miR‐182 was overexpressed in gastric cancer cell lines, both the mRNA and protein levels of CREB1 were depressed. Furthermore, CREB1 was present at a high level in human gastric adenocarcinoma tissues, and this was inversely correlated with miR‐182 expression. Ectopic expression of CREB1 overcame the suppressive phenotypes of gastric cancer cells caused by miR‐182. These results indicate that miR‐182 targets the CREB1 gene and suppresses gastric adenocarcinoma cell growth, suggesting that miR‐182 shows tumor‐suppressive activity in human gastric cancer.

BackgroundCD133 (Prominin) is widely used as a marker for the identification and isolation of neural precursor cells from normal brain or tumor tissue. However, the assumption that CD133 is expressed constitutively in neural precursor cells has not been examined.Methodology/Principal FindingsIn this study, we demonstrate that CD133 and a second marker CD15 are expressed heterogeneously in uniformly undifferentiated human neural stem (NS) cell cultures. After fractionation by flow cytometry, clonogenic tripotent cells are found in populations negative or positive for either marker. We further show that CD133 is down-regulated at the mRNA level in cells lacking CD133 immunoreactivity. Cell cycle profiling reveals that CD133 negative cells largely reside in G1/G0, while CD133 positive cells are predominantly in S, G2, or M phase. A similar pattern is apparent in mouse NS cell lines. Compared to mouse NS cells, however, human NS cell cultures harbour an increased proportion of CD133 negative cells and display a longer doubling time. This may in part reflect a sub-population of slow- or non-cycling cells amongst human NS cells because we find that around 5% of cells do not take up BrdU over a 14-day labelling period. Non-proliferating NS cells remain undifferentiated and at least some of them are capable of re-entry into the cell cycle and subsequent continuous expansion.ConclusionsThe finding that a significant fraction of clonogenic neural stem cells lack the established markers CD133 and CD15, and that some of these cells may be dormant or slow-cycling, has implications for approaches to identify and isolate neural stem cells and brain cancer stem cells. Our data also suggest the possibility that CD133 may be specifically down-regulated during G0/G1, and this should be considered when this marker is used to identify and isolate other tissue and cancer stem cells.

The complete nucleotide sequence of the Morus mongolica chloroplast (cp) genome was reported and characterized in this study. The cp genome is a circular molecule of 158,459 bp containing a pair of 25,678 bp IR regions, separated by small and large single-copy regions of 19,736 and 87,363 bp, respectively. The number and relative positions of the 114 unique genes (80 PCGs, 30 tRNAs, and 4 rRNA genes) are almost identical to Morus indica cp genome. Further detailed comparative analyses revealed one hypervariable region, which is responsible for 88% of the total variation, and 64 indel events between two individuals. There are 78 simple sequence repeats (SSRs) in M. mongolica cp genome, in which 58 of them are mononucleotide repeats. Comparative analysis with M. indica cp genome indicated 22 SSRs with length polymorphisms and 1 SSR with nucleotide content polymorphism. The phylogenetic analysis of 60 PCGs from 62 cp genomes provided strong support for the monophyletic, single origin of Fabidae (N2-fixing) clade.

SummaryMicroRNAs are a class of small endogenous non-coding RNAs that function as post-transcriptional regulators. In our previous study, we found that miR-181b was significantly downregulated in human gastric adenocarcinoma tissue samples compared to the adjacent normal gastric tissues. In this study, we confirm the down-regulation of miR-181b in human gastric cancer cell lines versus the gastric epithelial cells. Overexpression of miR-181b suppressed the proliferation and colony formation rate of gastric cancer cells. miR-181b downregulated the expression of cAMP responsive element binding protein 1 (CREB1) by binding its 3' untranslated region. Overexpression of CREB1 counteracted the suppression of growth in gastric cancer cells caused by ectopic expression of miR-181b. These results indicate that miR-181b may function as a tumor suppressor in gastric adenocarcinoma cells through negative regulation of CREB1. Abbreviations ASO, antisense oligonucleotide; CREB1, cAMP responsive element binding protein 1; EGFP, enhanced green fluorescence protein; GAPDH, glyceraldehyde phosphate dehydrogenase; miR-181b, microRNA181b; miRNA, microRNA; UTR, untranslated region.