Drosophila p120-catenin is crucial for endocytosis of the dynamic E-cadherin-Bazooka complex.

The intracellular functions of classical cadherins are mediated through the direct binding of two catenins: β-catenin and p120-catenin (also known as CTNND1 in vertebrates, and p120ctn in Drosophila). Whereas β-catenin is crucial for cadherin function, the role of p120-catenin is less clear and appears to vary between organisms. We show here that p120-catenin has a conserved role in regulating the endocytosis of cadherins, but that its ancestral role might have been to promote endocytosis, followed by the acquisition of a new inhibitory role in vertebrates. In Drosophila, p120-catenin facilitates endocytosis of the dynamic E-cadherin-Bazooka subcomplex, which is followed by its recycling. The absence of p120-catenin stabilises this subcomplex at the membrane, reducing the ability of cells to exchange neighbours in embryos and expanding cell-cell contacts in imaginal discs.We thank John Overton, the Gurdon Institute Imaging Facility, Maria J. Gomez-Lamarca, and Benjamin Klapholz for their help. Supported by BBSRC grant BB/K00056X/1.This is the final version of the article. It first appeared from The Company of Biologists via http://dx.doi.org/10.1242/jcs.17752

Microtubule organization is determined by the shape of epithelial cells.

Interphase microtubule organization is critical for cell function and tissue architecture. In general, physical mechanisms are sufficient to drive microtubule organization in single cells, whereas cells within tissues are thought to utilize signalling mechanisms. By improving the imaging and quantitation of microtubule alignment within developing Drosophila embryos, here we demonstrate that microtubule alignment underneath the apical surface of epithelial cells follows cell shape. During development, epidermal cell elongation and microtubule alignment occur simultaneously, but by perturbing cell shape, we discover that microtubule organization responds to cell shape, rather than the converse. A simple set of microtubule behaviour rules is sufficient for a computer model to mimic the observed responses to changes in cell surface geometry. Moreover, we show that microtubules colliding with cell boundaries zip-up or depolymerize in an angle-dependent manner, as predicted by the model. Finally, we show microtubule alignment responds to cell shape in diverse epithelia.This work was supported by grant BB/K00056X/1 from the UK Biotechnology, Biological Sciences Research Council. Gurdon Institute core funding was provided by the Wellcome Trust (092096) and Cancer Research UK (C6946/A14492). L.C. was supported by the Royal Society of Edinburgh/Scottish Government

Targeting of Drosophila Rhodopsin Requires Helix 8 but Not the Distal C-Terminus

BACKGROUND: The fundamental role of the light receptor rhodopsin in visual function and photoreceptor cell development has been widely studied. Proper trafficking of rhodopsin to the photoreceptor membrane is of great importance. In human, mutations in rhodopsin involving its intracellular mislocalization, are the most frequent cause of autosomal dominant Retinitis Pigmentosa, a degenerative retinal pathology characterized by progressive blindness. Drosophila is widely used as an animal model in visual and retinal degeneration research. So far, little is known about the requirements for proper rhodopsin targeting in Drosophila. METHODOLOGY/PRINCIPAL FINDINGS: Different truncated fly-rhodopsin Rh1 variants were expressed in the eyes of Drosophila and their localization was analyzed in vivo or by immunofluorescence. A mutant lacking the last 23 amino acids was found to properly localize in the rhabdomeres, the light-sensing organelle of the photoreceptor cells. This constitutes a major difference to trafficking in vertebrates, which involves a conserved QVxPA motif at the very C-terminus. Further truncations of Rh1 indicated that proper localization requires the last amino acid residues of a region called helix 8 following directly the last transmembrane domain. Interestingly, the very C-terminus of invertebrate visual rhodopsins is extremely variable but helix 8 shows conserved amino acid residues that are not conserved in vertebrate homologs. CONCLUSIONS/SIGNIFICANCE: Despite impressive similarities in the folding and photoactivation of vertebrate and invertebrate visual rhodopsins, a striking difference exists between mammalian and fly rhodopsins in their requirements for proper targeting. Most importantly, the distal part of helix 8 plays a central role in invertebrates. Since the last amino acid residues of helix 8 are dispensable for rhodopsin folding and function, we propose that this domain participates in the recognition of targeting factors involved in transport to the rhabdomeres

Typhoid toxin exhausts the RPA response to DNA replication stress driving senescence and Salmonella infection.

Salmonella Typhi activates the host DNA damage response through the typhoid toxin, facilitating typhoid symptoms and chronic infections. Here we reveal a non-canonical DNA damage response, which we call RING (response induced by a genotoxin), characterized by accumulation of phosphorylated histone H2AX (γH2AX) at the nuclear periphery. RING is the result of persistent DNA damage mediated by toxin nuclease activity and is characterized by hyperphosphorylation of RPA, a sensor of single-stranded DNA (ssDNA) and DNA replication stress. The toxin overloads the RPA pathway with ssDNA substrate, causing RPA exhaustion and senescence. Senescence is also induced by canonical γΗ2ΑΧ foci revealing distinct mechanisms. Senescence is transmitted to non-intoxicated bystander cells by an unidentified senescence-associated secreted factor that enhances Salmonella infections. Thus, our work uncovers a mechanism by which genotoxic Salmonella exhausts the RPA response by inducing ssDNA formation, driving host cell senescence and facilitating infection

Dynamic microtubules produce an asymmetric E-cadherin-Bazooka complex to maintain segment boundaries.

Distributing junctional components around the cell periphery is key for epithelial tissue morphogenesis and homeostasis. We discovered that positioning of dynamic microtubules controls the asymmetric accumulation of E-cadherin. Microtubules are oriented preferentially along the dorso-ventral axis in Drosophila melanogaster embryonic epidermal cells, and thus more frequently contact E-cadherin at dorso-ventral cell-cell borders. This inhibits RhoGEF2, reducing membrane recruitment of Rho-kinase, and increasing a specific E-cadherin pool that is mobile when assayed by fluorescence recovery after photobleaching. This mobile E-cadherin is complexed with Bazooka/Par-3, which in turn is required for normal levels of mobile E-cadherin. Mobile E-cadherin-Bazooka prevents formation of multicellular rosette structures and cell motility across the segment border in Drosophila embryos. Altogether, the combined action of dynamic microtubules and Rho signaling determines the level and asymmetric distribution of a mobile E-cadherin-Bazooka complex, which regulates cell behavior during the generation of a patterned epithelium

Harbiye bakanının tamimi!

Taha Toros Arşivi, Dosya Adı: Milli Mücadele İstiklal Harbi GazetesiUnutma İstanbul projesi İstanbul Kalkınma Ajansı'nın 2016 yılı "Yenilikçi ve Yaratıcı İstanbul Mali Destek Programı" kapsamında desteklenmiştir. Proje No: TR10/16/YNY/010

Unraveling the Genetic Complexity of Drosophila stardust During Photoreceptor Morphogenesis and Prevention of Light-Induced Degeneration

Drosophila Stardust, a membrane-associated guanylate kinase (MAGUK), recruits the transmembrane protein Crumbs and the cytoplasmic proteins DPATJ and DLin-7 into an apically localized protein scaffold. This evolutionarily conserved complex is required for epithelial cell polarity in Drosophila embryos and mammalian cells in culture. In addition, mutations in Drosophila crumbs and DPATJ impair morphogenesis of photoreceptor cells (PRCs) and result in light-dependent retinal degeneration. Here we show that stardust is a genetically complex locus. While all alleles tested perturb epithelial cell polarity in the embryo, only a subset of them affects morphogenesis of PRCs or induces light-dependent retinal degeneration. Alleles retaining particular postembryonic functions still express some Stardust protein in pupal and/or adult eyes. The phenotypic complexity is reflected by the expression of distinct splice variants at different developmental stages. All proteins expressed in the retina contain the PSD95, Discs Large, ZO-1 (PDZ), Src homology 3 (SH3), and guanylate kinase (GUK) domain, but lack a large region in the N terminus encoded by one exon. These results suggest that Stardust-based protein scaffolds are dynamic, which is not only mediated by multiple interaction partners, but in addition by various forms of the Stardust protein itself

Data file for the submitted publication "Robustness of the microtubule network self-organization in epithelia"

Combining mathematical modelling with genetic manipulations in Drosophila, we show that the microtubule self-organization indeed does not depend on dynamics of individual microtubules, and thus is robust on the tissue level.Bulgakova, Natalia A; Ramírez Moreno, Miguel.(2019). Data file for the submitted publication "Robustness of the microtubule network self-organization in epithelia", [dataset]. University of Edinburgh. School of Mathematics. https://doi.org/10.7488/ds/2642

Body Height of Children with Bronchial Asthma of Various Severities

Influence of bronchial asthma (BA) severity on physical development in children patients was evaluated in comparison with healthy population. Materials and Methods. 1042 children and adolescents (768 boys) with atopic BA were evaluated. All children underwent standard examination in a clinical setting, including anthropometry. The control group included 875 healthy children of a comparable age (423 boys). Results. The fraction of patients with the normal, lower, and increased height among the whole group of patients with BA is close to the corresponding values in the healthy population (χ2=3.32, p=0.65). The fraction of BA patients with the reduced physical development is increased monotonically and significantly when the BA severity increases: healthy group, 8.2% (72/875), BA intermittent, 4.2% (6/144), BA mild persistent 9% (47/520), BA moderate persistent, 11.7% (36/308), and BA severe persistent, 24.3% (17/70) (χ2=45.6, p=0,0009). Conclusion. The fraction of the children with the reduced height is increased monotonically and significantly in the groups of increasing BA severities. At the same time, the fraction of such children in groups of intermittent and mild persistent BA practically does not differ from the conditionally healthy peers

Hematologic Features of Children and Adolescent Patients with Acute Hypersensitivity Reactions on Drugs and Food

Hematological parameters and blood biochemical markers were measured in 131 children and adolescent patients (70 boys) aged 2 to 17 years with acute hypersensitivity reactions induced by food (59 patients) and medicines (72 patients) in order to establish differences in clinical manifestations and hematological parameters in children with food and drug hypersensitivity and to elaborate the hematological criteria for differentiating the possible pathophysiological mechanisms of various types of hypersensitivity. Both groups of patients had comparable clinical symptoms with a predominance of skin lesions. The significant differences between the groups with drug- and food-induced hypersensitivity reactions were found in their red blood characteristics. In patients with hypersensitive reactions to drugs, significantly lower levels of erythrocytes and hemoglobin were found, while the median values of these parameters did not exceed the limits of reference values. These differences persisted also in the analysis of hemoglobin values, analyzed with accounting for the age and sex of patients. The reduction of hemoglobin was not accompanied by an increase in bilirubin in these patients. Thus, this fact does not support the assumption about the drug-induced hemolysis as a main effect influencing the hematological parameters. Hemogram evaluation performed during 7–10 days after admission demonstrated a higher level of hemoglobin in both groups. The biochemical markers were not significantly distinguished except bilirubin and alkaline phosphatase which were higher in patients with food-induced hypersensitivity