A stromal lineage maintains crypt structure and villus homeostasis in the intestinal stem cell niche.

BACKGROUND: The nutrient-absorbing villi of small intestines are renewed and repaired by intestinal stem cells (ISCs), which reside in a well-organized crypt structure. Genetic studies have shown that Wnt molecules secreted by telocytes, Gli1+ stromal cells, and epithelial cells are required for ISC proliferation and villus homeostasis. Intestinal stromal cells are heterogeneous and single-cell profiling has divided them into telocytes/subepithelial myofibroblasts, myocytes, pericytes, trophocytes, and Pdgfralow stromal cells. Yet, the niche function of these stromal populations remains incompletely understood. RESULTS: We show here that a Twist2 stromal lineage, which constitutes the Pdgfralow stromal cell and trophocyte subpopulations, maintains the crypt structure to provide an inflammation-restricting niche for regenerating ISCs. Ablating Twist2 lineage cells or deletion of one Wntless allele in these cells disturbs the crypt structure and impairs villus homeostasis. Upon radiation, Wntless haplo-deficiency caused decreased production of anti-microbial peptides and increased inflammation, leading to defective ISC proliferation and crypt regeneration, which were partially rescued by eradication of commensal bacteria. In addition, we show that Wnts secreted by Acta2+ subpopulations also play a role in crypt regeneration but not homeostasis. CONCLUSIONS: These findings suggest that ISCs may require different niches for villus homeostasis and regeneration and that the Twist2 lineage cells may help to maintain a microbe-restricted environment to allow ISC-mediated crypt regeneration.

c-Abl regulates gastrointestinal muscularis propria homeostasis via ERKs.

The gastrointestinal tract is responsible for food digestion and absorption. The muscularis propria propels the foodstuff through the GI tract and defects in intestine motility may cause obstruction disorders. Our present genetic studies identified non-receptor tyrosine kinase c-Abl as an important regulator of the muscularis propria homeostasis and a risk factor for rectal prolapse. Mouse deficient for c-Abl showed defects in the muscularis propria of gastrointestinal tract and older c-Abl -/- mice developed megaesophagus and rectal prolapse. Inhibition of c-Abl with imatinib mesylate, an anti-CML drug, or ablation of c-Abl using Prx1-Cre, which marks smooth muscle cells, recapitulated most of the muscularis propria phenotypes. The pathogenesis of rectal prolapse was attributable to overproliferation of smooth muscle cells, which was caused by enhanced ERK1/2 activation. Administration of ERK inhibitor U0126 impeded the development of rectal prolapse in c-Abl deficient mice. These results reveal a role for c-Abl-regulated smooth muscle proliferation in the pathogenesis of rectal prolapse, and imply that long-term use of imatinib mesylate may cause gastrointestinal problems in patients while ERK inhibitor may be effective in treating rectal prolapse.

A microarray-based approach identifies ADP ribosylation factor-like protein 2 as a target of microRNA-16.

microRNAs (miRNAs) are generally thought to negatively regulate the expression of their target genes by mRNA degradation or by translation repression. Here we show an efficient way to identify miRNA target genes by screening alterations in global mRNA levels following changes in miRNA levels. In this study, we used mRNA microarrays to measure global mRNA expression in three cell lines with increased or decreased levels of miR-16 and performed bioinformatics analysis based on multiple target prediction algorithms. For further investigation among the predicted miR-16 target genes, we selected genes that show an expression pattern opposite to that of miR-16. One of the candidate target genes that may interact with miR-16, ADP-ribosylation factor-like protein 2 (ARL2), was further investigated. First, ARL2 was deduced to be an ideal miR-16 target by computational predictions. Second, ARL2 mRNA and protein levels were significantly abolished by treatment with miR-16 precursors, whereas a miR-16 inhibitor increased ARL2 mRNA and protein levels. Third, a luciferase reporter assay confirmed that miR-16 directly recognizes the 3'-untranslated region (3'-UTR) of ARL2. Finally, we showed that miR-16 could regulate proliferation and induce a significant G0/G1 cell cycle arrest, which was due at least in part, to the down-regulation of ARL2. In summary, the present study suggests that integrating global mRNA profiling and bioinformatics tools may provide the basis for further investigation of the potential targets of a given miRNA. These results also illustrate a novel function of miR-16 targeting ARL2 in modulating proliferation and cell cycle progression.

Identification of miRNAs that are associated with tumor metastasis in neuroblastoma.

The discovery of microRNAs (miRNAs) has opened a new avenue for both diagnosis and treatment of cancers. Accumulating experimental evidences indicate that miRNAs are aberrantly expressed in different tumor types and have a critical role in tumorigenesis. However, the miRNA expression profile in neuroblastoma (NB), one of the most common cancer forms in children, has not been well characterized. In the present study, we established a heterotopic transplant mice model of NB and employed miRNA microarray analysis to identify miRNAs that are differentially expressed in metastatic NB compared to primary NB. A list of 54 miRNAs was found to be significantly altered in metastatic tumors compared to primary tumors. These differentially-expressed miRNAs were selectively validated by a stem-loop qRT-PCR assay. Furthermore, we predicted a list of potential miRNA-target pairs that may be involved in the metastasis of neuroblastoma by three different computer-aided algorithms. Taken together, our results indicate that a unique panel of miRNAs are associated with metastatic NB and these differentially-expressed miRNAs may play an important role in the NB metastatic process. This finding may also shed light in our understanding of the nature of metastatic NB and provide a potential novel target for therapeutic treatment of this tumor.

In vitro evidence suggests that miR-133a-mediated regulation of uncoupling protein 2 (UCP2) is an indispensable step in myogenic differentiation.

UCP2 and UCP3, two novel uncoupling proteins, are important regulators of energy expenditure and thermogenesis in various organisms. The striking disparity between UCP2 mRNA and protein levels in muscle tissues prompted initial speculation that microRNAs are implicated in the regulatory pathway of UCP2. We found, for the first time, that the repression of UCP2 expression in cardiac and skeletal muscle resulted from its targeting by a muscle-specific microRNA, miR-133a. Moreover, our findings illustrate a novel function of UCP2 as a brake for muscle development. We also show that MyoD can remove the braking role of UCP2 via direct up-regulation of miR-133a during myogenic differentiation. Taken together, our current work delineates a novel regulatory network employing MyoD, microRNA, and uncoupling proteins to fine-tune the balance between muscle differentiation and proliferation during myogenesis.

Characterization of microRNAs in serum: a novel class of biomarkers for diagnosis of cancer and other diseases.

Dysregulated expression of microRNAs (miRNAs) in various tissues has been associated with a variety of diseases, including cancers. Here we demonstrate that miRNAs are present in the serum and plasma of humans and other animals such as mice, rats, bovine fetuses, calves, and horses. The levels of miRNAs in serum are stable, reproducible, and consistent among individuals of the same species. Employing Solexa, we sequenced all serum miRNAs of healthy Chinese subjects and found over 100 and 91 serum miRNAs in male and female subjects, respectively. We also identified specific expression patterns of serum miRNAs for lung cancer, colorectal cancer, and diabetes, providing evidence that serum miRNAs contain fingerprints for various diseases. Two non-small cell lung cancer-specific serum miRNAs obtained by Solexa were further validated in an independent trial of 75 healthy donors and 152 cancer patients, using quantitative reverse transcription polymerase chain reaction assays. Through these analyses, we conclude that serum miRNAs can serve as potential biomarkers for the detection of various cancers and other diseases.

[Polymorphism distributions of 9 microsatellite Loci in Chinese merino sheep].

The polymorphism distributions of nine microsatellite loci, BM6506, BM1824, BM6438, ILSTS004 and OarDB6 on Chinese merino sheep chromosome 1 and BM4621, OarHH55, BM143 and OarJMP8 in sheep chromosome 6 were determined by polymerase chain reaction (PCR) and multiplex gel electrophoresis followed by silver staining. Gene frequency (Pi), power of discrimination (DP), heterozygosity (H), polymorphism information content (PIC) and probability of paternity exclusion (PE) were calculated. All loci obeyed Hardy-Weinberg equilibrium. BM4621 displayed the highest DP, H, PIC and PE values among the nine microsatellite loci. Cumulative DP of the nine microsatellite loci is 0.99999 and cumulative PE is 0.99915. These results showed that the nine microsatellite loci could be used in linkage analysis, individual identification and paternity test in Chinese merino sheep.