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Hedgehog (Hh) pathway inhibitors are clinically effective in treatment of basal cell carcinoma and medulloblastoma, but fail therapeutically or accelerate progression in treatment of endodermally derived colon and pancreatic cancers. In bladder, another organ of endodermal origin, we find that despite its initial presence in the cancer cell of origin Sonic hedgehog (Shh) expression is invariably lost during progression to invasive urothelial carcinoma. Genetic blockade of stromal response to Shh furthermore dramatically accelerates progression and decreases survival time. This cancer-restraining effect of Hh pathway activity is associated with stromal expression of BMP signals, which stimulate urothelial differentiation. Progression is dramatically reduced by pharmacological activation of BMP pathway activity with low-dose FK506, suggesting an approach to management of human bladder cancer.

Epithelial integrity in metazoan organs is maintained through the regulated proliferation and differentiation of organ-specific stem and progenitor cells. Although the epithelia of organs such as the intestine regenerate constantly and thus remain continuously proliferative (1), other organs, such as the mammalian urinary bladder, shift from near-quiescence to a highly proliferative state in response to epithelial injury (2-4). The cellular and molecular mechanisms underlying this injury-induced mode of regenerative response are poorly defined. Here we show in mice that the proliferative response to bacterial infection or chemical injury within the bladder is regulated by signal feedback between basal cells of the urothelium and the stromal cells that underlie them. We demonstrate that these basal cells include stem cells capable of regenerating all cell types within the urothelium, and are marked by expression of the secreted protein signal Sonic hedgehog (Shh). On injury, Shh expression in these basal cells increases and elicits increased stromal expression of Wnt protein signals, which in turn stimulate the proliferation of both urothelial and stromal cells. The heightened activity of this signal feedback circuit and the associated increase in cell proliferation appear to be required for restoration of urothelial function and, in the case of bacterial injury, may help clear and prevent further spread of infection. Our findings provide a conceptual framework for injury-induced epithelial regeneration in endodermal organs, and may provide a basis for understanding the roles of signalling pathways in cancer growth and metastasis., The multi-layered bladder epithelium consists of a lumenal layer of fully differentiated, usually binucleate umbrella cells (5), which overlie intermediate cells with limited proliferative potential, and long-term label-retaining basal cells [...]

Membrane-associated guanylate kinase (Maguk) proteins are scaffold proteins that contain PSD-95-Discs Large-zona occludens-1 (PDZ), Src homology 3, and guanylate kinase domains. A subset of Maguk proteins, such as mLin-2 and protein associated with Lin-7 (Pals)1, also contain two L27 domains: an L27C domain that binds mLin-7 and an L27N domain of unknown function. Here, we demonstrate that the L27N domain targets Pals1 to tight junctions by binding to a PDZ domain protein, Pals1-associated tight junction (PATJ) protein, via a unique Maguk recruitment domain. PATJ is a homologue of Drosophila Discs Lost, a protein that is crucial for epithelial polarity and that exists in a complex with the apical polarity determinant, Crumbs. PATJ and a human Crumbs homologue, CRB1, colocalize with Pals1 to tight junctions, and CRB1 interacts with PATJ albeit indirectly via binding the Pals1 PDZ domain. In agreement, we find that a Drosophila homologue of Pals1 participates in identical interactions with Drosophila Crumbs and Discs Lost. This Drosophila Pals1 homologue has been demonstrated recently to represent Stardust, a crucial polarity gene in Drosophila. Thus, our data identifies a new multiprotein complex that appears to be evolutionarily conserved and likely plays an important role in protein targeting and cell polarity.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2006.08.005 Byline: Kunyoo Shin (1), Ben Margolis (1) Abstract: The tight junction is an intricate seal between adjoining epithelial cells that also separates the apical and basolateral membranes within these cells. A paper in this issue of Cell by demonstrates that loss of the ZO scaffolding proteins prevents the formation of tight junctions but surprisingly does not perturb apico-basal polarity. Author Affiliation: (1) Department of Internal Medicine and Biological Chemistry, University of Michigan Medical School, Ann Arbor, MI 48109, USA

Recent advancements in organoid technology have led to a vigorous movement towards utilizing it as a substitute for animal experiments. Organoid technology offers versatile applications, particularly in toxicity testing of pharmaceuticals or chemical substances. However, for the practical use in toxicity testing, minimal guidance is required to ensure reliability and relevance. This paper aims to provide minimal guidelines for practical uses of kidney organoids derived from human pluripotent stem cells as a toxicity evaluation model in vitro .

Latent transforming growth factor (TGF)-beta-binding protein (LTBP) is required for the assembly, secretion, matrix association, and activation of latent TGF-beta complex. To elucidate the cell specific expression of the genes of LTBP-1 and their splice variants and the factors that regulate the gene expression, we cultured primary human glomerular endothelial cells (HGEC) under different conditions. Basal expression of LTBP-1 mRNA was suppressed in HGEC compared to WI-38 human embryonic lung fibroblasts. High glucose, H(2)O(2), and TGF-beta1 upregulated and vascular endothelial growth factor (VEGF) further downregulated LTBP-1 mRNA in HGEC. RT-PCR with a primer set for LTBP-1S produced many clones but no clone was gained with a primer set for LTBP-1L. Of 12 clones selected randomly, Sca I mapping and DNA sequencing revealed that only one was LTBP-1S and all the others were LTBP-1Sdelta53. TGF-beta1, but not high glucose, H(2)O(2) or VEGF, tended to increase LTBP-1Sdelta53 mRNA. In conclusion, HGEC express LTBP-1 mRNA which is suppressed at basal state but upregulated by high glucose, H(2)O(2), and TGF-beta1 and downregulated by VEGF. Major splice variant of LTBP-1 in HGEC was LTBP-1S 53. Modification of LTBP-1S 53 gene in HGEC may abrogate fibrotic action of TGF-beta1 but this requires confirmation.

Although the genes that encode the glutamyl-tRNA(Gln) (Glu-tRNA(Gln)) specific amidotransferase (Glu-AdTase) from various bacteria and eukaryotic organelles are known, the precise mechanism of the enzyme is still unclear. One of the reasons is that there is no information on the three-dimensional structure of the complex, the Glu-AdTase:Glu-tRNA(Gln):ATP:amino group donor. To obtain the crystals of Glu-AdTase, the Glu-AdTase of Bacillus stearothermophilus was overexpressed and purified after cloning of the gene that encodes the enzyme. The cloned DNA contained the full-length gene cluster that represented the Glu-AdTase of B. stearothermophilus, and was organized as an operon that consisted of three open-reading frames (ORFs). The order of the genes was gatCAB, as shown in Bacillus subtilis. The ORFs showed a high amino-acid homology to those of B. subtilis (A subunit, 73.2%; B subunit, 81.6%; C subunit, 69.5%) and Staphylococcus aureus (A subunit, 61.9%; B subunit, 71.8%; C subunit, 45.9%). The ORFs were re-cloned on the overexpression vector, pTrc99a, and a recombinant pTrcgatCABBST was obtained. The Glu-AdTase that was overexpressed with pTrcgatCABBST in Escherichia coli retained transamidation activity on the mischarged glutamic acid on the tRNA(Gln). It also produced correctly-charged Gln-tRNA(Gln) at 37, 42, and 50 degrees C. Although Glu-AdTases from both B. subtilis and B. stearothermophilus were subjected to crystallization, the micro-crystals were only obtained from the B. stearothermophilus enzyme.