An RNA interference phenotypic screen identifies a role for FGF signals in colon cancer progression

In tumor cells, stepwise oncogenic deregulation of signaling cascades induces alterations of cellular morphology and promotes the acquisition of malignant traits. Here, we identified a set of 21 genes, including FGF9, as determinants of tumor cell morphology by an RNA interference phenotypic screen in SW480 colon cancer cells. Using a panel of small molecular inhibitors, we subsequently established phenotypic effects, downstream signaling cascades, and associated gene expression signatures of FGF receptor signals. We found that inhibition of FGF signals induces epithelial cell adhesion and loss of motility in colon cancer cells. These effects are mediated via the mitogen-activated protein kinase (MAPK) and Rho GTPase cascades. In agreement with these findings, inhibition of the MEK1/2 or JNK cascades, but not of the PI3K-AKT signaling axis also induced epithelial cell morphology. Finally, we found that expression of FGF9 was strong in a subset of advanced colon cancers, and overexpression negatively correlated with patients' survival. Our functional and expression analyses suggest that FGF receptor signals can contribute to colon cancer progression.     

IL-22 is produced by innate lymphoid cells and limits inflammation in allergic airway disease

Interleukin (IL)-22 is an effector cytokine, which acts primarily on epithelial cells in the skin, gut, liver and lung. Both pro- and anti-inflammatory properties have been reported for IL-22 depending on the tissue and disease model. In a murine model of allergic airway inflammation, we found that IL-22 is predominantly produced by innate lymphoid cells in the inflamed lungs, rather than TH cells. To determine the impact of IL-22 on airway inflammation, we used allergen-sensitized IL-22-deficient mice and found that they suffer from significantly higher airway hyperreactivity upon airway challenge. IL-22-deficiency led to increased eosinophil infiltration lymphocyte invasion and production of CCL17 (TARC), IL-5 and IL-13 in the lung. Mice treated with IL-22 before antigen challenge displayed reduced expression of CCL17 and IL-13 and significant amelioration of airway constriction and inflammation. We conclude that innate IL-22 limits airway inflammation, tissue damage and clinical decline in allergic lung disease.     

Differential in vivo binding dynamics of somatic and oocyte-specific linker histones in oocytes and during ES cell nuclear transfer

The embryonic genome is formed by fusion of a maternal and a paternal genome. To accommodate the resulting diploid genome in the fertilized oocyte dramatic global genome reorganizations must occur. The higher order structure of chromatin in vivo is critically dependent on architectural chromatin proteins, with the family of linker histone proteins among the most critical structural determinants. Although somatic cells contain numerous linker histone variants, only one, H1FOO, is present in mouse oocytes. Upon fertilization H1FOO rapidly populates the introduced paternal genome and replaces sperm-specific histone-like proteins. The same dynamic replacement occurs upon introduction of a nucleus during somatic cell nuclear transfer. To understand the molecular basis of this dynamic histone replacement process, we compared the localization and binding dynamics of somatic H1 and oocyte-specific H1FOO and identified the molecular determinants of binding to either oocyte or somatic chromatin in living cells. We find that although both histones associate readily with chromatin in nuclei of somatic cells, only H1FOO is capable of correct chromatin association in the germinal vesicle stage oocyte nuclei. This specificity is generated by the N-terminal and globular domains of H1FOO. Measurement of in vivo binding properties of the H1 variants suggest that H1FOO binds chromatin more tightly than somatic linker histones. We provide evidence that both the binding properties of linker histones as well as additional, active processes contribute to the replacement of somatic histones with H1FOO during nuclear transfer. These results provide the first mechanistic insights into the crucial step of linker histone replacement as it occurs during fertilization and somatic cell nuclear transfer.     

Scaling of mammalian ethmoid bones can predict olfactory organ size and performance

The relation between size and performance is central for understanding the evolution of sensory systems, and much interest has been focused on mammalian eyes and ears. However, we know very little about olfactory organ size (OOS), as data for a representative set of mammals are lacking. Here, we present a cranial endocast method for estimating OOS by measuring an easily accessible part of the system, the perforated part of the ethmoid bone, through which the primary olfactory axons reach the olfactory bulb. In 16 species, for which relevant data are available, the area of the perforated ethmoid bone is directly proportional to the area of the olfactory epithelium. Thus, the ethmoid bone is a useful indicator enabling us to analyse 150 species, and describe the distribution of OOS within the class Mammalia. In the future, a method using skull material may be applied to fossil skulls. In relation to skull size, humans, apes and monkeys have small olfactory organs, while prosimians have OOSs typical for mammals of their size. Large ungulates have impressive olfactory organs. Relating anatomy to published thresholds, we find that sensitivity increases with increasing absolute organ size.     

Normal mode-based fitting of atomic structure into electron density maps: application to sarcoplasmic reticulum Ca-ATPase

A method for the flexible docking of high-resolution atomic structures into lower resolution densities derived from electron microscopy is presented. The atomic structure is deformed by an iterative process using combinations of normal modes to obtain the best fit of the electron microscopical density. The quality of the computed structures has been evaluated by several techniques borrowed from crystallography. Two atomic structures of the SERCA1 Ca-ATPase corresponding to different conformations were used as a starting point to fit the electron density corresponding to a different conformation. The fitted models have been compared to published models obtained by rigid domain docking, and their relation to the known crystallographic structures are explored by normal mode analysis. We find that only a few number of modes contribute significantly to the transition. The associated motions involve almost exclusively rotation and translation of the cytoplasmic domains as well as displacement of cytoplasmic loops. We suggest that the movements of the cytoplasmic domains are driven by the conformational change that occurs between nonphosphorylated and phosphorylated intermediate, the latter being mimicked by the presence of vanadate at the phosphorylation site in the electron microscopy structure.     

Histidine 129 in the 75-kDa subunit of mitochondrial complex I from Yarrowia lipolytica is not a ligand for [Fe4S4] cluster N5 but is required for catalytic activity

Respiratory chain complex I contains 8-9 iron-sulfur clusters. In several cases, the assignment of these clusters to subunits and binding motifs is still ambiguous. To test the proposed ligation of the tetranuclear iron-sulfur cluster N5 of respiratory chain complex I, we replaced the conserved histidine 129 in the 75-kDa subunit from Yarrowia lipolytica with alanine. In the mutant strain, reduced amounts of fully assembled but destabilized complex I could be detected. Deamino-NADH: ubiquinone oxidoreductase activity was abolished completely by the mutation. However, EPR spectroscopic analysis of mutant complex I exhibited an unchanged cluster N5 signal, excluding histidine 129 as a cluster N5 ligand.