Lrig1 marks a population of gastric epithelial cells capable of long-term tissue maintenance and growth in vitro

The processes involved in renewal of the epithelium that lines the mouse stomach remain unclear. Apart from the cells in the isthmus, several other populations located deeper in the gastric glands have been suggested to contribute to the maintenance of the gastric epithelium. Here, we reveal that Lrig1 is expressed in the basal layer of the forestomach and the lower part of glands in the corpus and pylorus. In the glandular epithelium of the stomach, Lrig1 marks a heterogeneous population comprising mainly non-proliferative cells. Yet, fate-mapping experiments using a knock-in mouse line expressing Cre specifically in Lrig1(+) cells demonstrate that these cells are able to contribute to the long-term maintenance of the gastric epithelium. Moreover, when cultured in vitro, cells expressing high level of Lrig1 have much higher organoid forming potential than the corresponding cellular populations expressing lower levels of Lrig1. Taken together, these observations show that Lrig1 is expressed primarily by differentiated cells, but that these cells can be recruited to contribute to the maintenance of the gastric epithelium. This confirms previous observations that cells located in the lower segments of gastric glands can participate in tissue replenishment

Tumor-specific usage of alternative transcription start sites in colorectal cancer identified by genome-wide exon array analysis

<p>Abstract</p> <p>Background</p> <p>Approximately half of all human genes use alternative transcription start sites (TSSs) to control mRNA levels and broaden the transcriptional output in healthy tissues. Aberrant expression patterns promoting carcinogenesis, however, may arise from alternative promoter usage.</p> <p>Results</p> <p>By profiling 108 colorectal samples using exon arrays, we identified nine genes (<it>TCF12, OSBPL1A, TRAK1, ANK3, CHEK1, UGP2, LMO7, ACSL5</it>, and <it>SCIN</it>) showing tumor-specific alternative TSS usage in both adenoma and cancer samples relative to normal mucosa. Analysis of independent exon array data sets corroborated these findings. Additionally, we confirmed the observed patterns for selected mRNAs using quantitative real-time reverse-transcription PCR. Interestingly, for some of the genes, the tumor-specific TSS usage was not restricted to colorectal cancer. A comprehensive survey of the nine genes in lung, bladder, liver, prostate, gastric, and brain cancer revealed significantly altered mRNA isoform ratios for <it>CHEK1, OSBPL1A</it>, and <it>TCF12 </it>in a subset of these cancer types.</p> <p>To identify the mechanism responsible for the shift in alternative TSS usage, we antagonized the Wnt-signaling pathway in DLD1 and Ls174T colorectal cancer cell lines, which remarkably led to a shift in the preferred TSS for both <it>OSBPL1A </it>and <it>TRAK1</it>. This indicated a regulatory role of the Wnt pathway in selecting TSS, possibly also involving TP53 and SOX9, as their transcription binding sites were enriched in the promoters of the tumor preferred isoforms together with their mRNA levels being increased in tumor samples.</p> <p>Finally, to evaluate the prognostic impact of the altered TSS usage, immunohistochemistry was used to show deregulation of the total protein levels of both TCF12 and OSBPL1A, corresponding to the mRNA levels observed. Furthermore, the level of nuclear TCF12 had a significant correlation to progression free survival in a cohort of 248 stage II colorectal cancer samples.</p> <p>Conclusions</p> <p>Alternative TSS usage in colorectal adenoma and cancer samples has been shown for nine genes, and <it>OSBPL1A </it>and <it>TRAK1 </it>were found to be regulated <it>in vitro </it>by Wnt signaling. TCF12 protein expression was upregulated in cancer samples and correlated with progression free survival.</p

Heterogeneity and plasticity of epidermal stem cells

The epidermis is an integral part of our largest organ, the skin, and protects us against the hostile environment. It is a highly dynamic tissue that, during normal steady-state conditions, undergoes constant turnover. Multiple stem cell populations residing in autonomously maintained compartments facilitate this task. In this Review, we discuss stem cell behaviour during normal tissue homeostasis, regeneration and disease within the pilosebaceous unit, an integral structure of the epidermis that is responsible for hair growth and lubrication of the epithelium. We provide an up-to-date view of the pilosebaceous unit, encompassing the heterogeneity and plasticity of multiple discrete stem cell populations that are strongly influenced by external cues to maintain their identity and function

Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling-6

<p><b>Copyright information:</b></p><p>Taken from "Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling"</p><p>http://www.jmolecularsignaling.com/content/2/1/6</p><p>Journal of Molecular Signaling 2007;2():6-6.</p><p>Published online 16 Jul 2007</p><p>PMCID:PMC1976611.</p><p></p>after induction of dnTCFs in LS174T derived cell lines. Expression levels were normalized to the Ubiquitin C (UBC) transcript. The CLU34 mRNA variant is specifically up-regulated in response to dnTCF1 over-expression in LS174T cells. Data are presented as the mean ± standard deviation from 2 separate experiments with each experiment consisting of the mean value of 3 independent determinations. c-MYC mRNA levels decrease, whereas p21mRNA levels increase after induction of both dnTCFs

Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling-0

<p><b>Copyright information:</b></p><p>Taken from "Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling"</p><p>http://www.jmolecularsignaling.com/content/2/1/6</p><p>Journal of Molecular Signaling 2007;2():6-6.</p><p>Published online 16 Jul 2007</p><p>PMCID:PMC1976611.</p><p></p>f GFP tagged E-cadherin and GFP as control. Immunofluorescence was used to show the effects of transient over-expression of GFP tagged E-cadherin, which binds β-catenin, in LS174T and HCT116 colon carcinoma cell lines. In the left panel it is shown that the GFP-cyt-E-cadherin fusion protein efficiently sequesters β-catenin from the nucleus whereupon Wnt signaling is abrogated. In transfected cells (white arrow heads) β-catenin has a perinuclear localization contrasting untransfected cells (white arrows) where it is uniformly distributed. Shown in the right panel is the up-regulation of cytoplasmic CLU protein which follows the abrogation of Wnt signaling induced by the GFP-cyt-E-cadherin fusion protein. CLU is up-regulated in GFP-cyt-E-cadherin transfected cells (yellow arrow heads) but not in untransfected cells nor in cells transfected with GFP alone. Western blot with cell lysates from LS174T cells 24 hr after transient transfection with GFP-cyt-E-cadherin and GFP as a control. β-actin was used as a loading control. CLU protein levels are up-regulated and c-MYC protein levels are down-regulated as a consequence of over-expressing GFP-cyt-E-cadherin but not GFP alone. WB: western blot, ab: Antibody

Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling-5

<p><b>Copyright information:</b></p><p>Taken from "Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling"</p><p>http://www.jmolecularsignaling.com/content/2/1/6</p><p>Journal of Molecular Signaling 2007;2():6-6.</p><p>Published online 16 Jul 2007</p><p>PMCID:PMC1976611.</p><p></p>ial TCF-binding sites (red arrows) predicted by the MatInspector software. Exonic structure of CLU mRNA variants

Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling-1

<p><b>Copyright information:</b></p><p>Taken from "Clusterin expression can be modulated by changes in TCF1-mediated Wnt signaling"</p><p>http://www.jmolecularsignaling.com/content/2/1/6</p><p>Journal of Molecular Signaling 2007;2():6-6.</p><p>Published online 16 Jul 2007</p><p>PMCID:PMC1976611.</p><p></p>the effectors of the Wnt pathway, were over-expressed in stably transfected LS174T derived cell lines. Proliferation was halted in LS174T derived cell lines after induction of both dnTCFs. This was visualised by methyl violet staining of cell cultures after 5 days of induction. Similar results were obtained by manually counting cells in a haemocytometer after cells had been cultured in the presence (+) or absence (-) of induction for 4 days. Data are presented as the mean ± standard deviation from 3 separate experiments. Induction of exogenous gene products, dnTCFs, was detected by western blot with cell lysates from LS174T derived cell lines 0, 12, and 24 hr after induction. Control cells are LS174T cells without any dnTCF expression vector. Both dnTCF1 and dnTCF4 abrogate β-catenin/TCF driven transcription of the Wnt-target gene, c-MYC, as analyzed by western blot with cell lysates from LS174T derived cell lines 0 and 12 hr after induction