Role of Scrib and Dlg in anterior-posterior patterning of the follicular epithelium during Drosophila oogenesis

<p>Abstract</p> <p>Background</p> <p>Proper patterning of the follicle cell epithelium over the egg chamber is essential for the <it>Drosophila </it>egg development. Differentiation of the epithelium into several distinct cell types along the anterior-posterior axis requires coordinated activities of multiple signaling pathways. Previously, we reported that <it>lethal(2)giant larvae </it>(<it>lgl</it>), a <it>Drosophila </it>tumor suppressor gene, is required in the follicle cells for the posterior follicle cell (PFC) fate induction at mid-oogenesis. Here we explore the role of another two tumor suppressor genes, <it>scribble </it>(<it>scrib</it>) and <it>discs large </it>(<it>dlg</it>), in the epithelial patterning.</p> <p>Results</p> <p>We found that removal of <it>scrib </it>or <it>dlg </it>function from the follicle cells at posterior terminal of the egg chamber causes a complete loss of the PFC fate. Aberrant specification and differentiation of the PFCs in the mosaic clones can be ascribed to defects in coordinated activation of the EGFR, JAK and Notch signaling pathways in the multilayered cells. Meanwhile, the clonal analysis revealed that loss-of-function mutations in <it>scrib/dlg </it>at the anterior domains result in a partially penetrant phenotype of defective induction of the stretched and centripetal cell fate, whereas specification of the border cell fate can still occur in the most anterior region of the mutant clones. Further, we showed that <it>scrib </it>genetically interacts with <it>dlg </it>in regulating posterior patterning of the epithelium.</p> <p>Conclusion</p> <p>In this study we provide evidence that <it>scrib </it>and <it>dlg </it>function differentially in anterior and posterior patterning of the follicular epithelium at oogenesis. Further genetic analysis indicates that <it>scrib </it>and <it>dlg </it>act in a common pathway to regulate PFC fate induction. This study may open another window for elucidating role of <it>scrib/dlg </it>in controlling epithelial polarity and cell proliferation during development.</p

GIS-based modelling of rock-ice avalanches from Alpine permafrost areas

Changing permafrost conditions caused by present atmospheric warming are expected to affect the stability of steep rock walls in high mountain areas. The possible increase in periglacial slope instabilities and the especially long potential run-out distances in glacial environments require more awareness about the kind of events as well as robust models to foresee areas affected and distances reached. A geographic information system-based flow-routing model is introduced for modelling rock-ice avalanches on a regional scale. The model application to three major historical events in the European Alps shows the basic use for simulating such events for first-order assessments. By designating the path of steepest descent while allowing lateral spreading from the fall track up to 45°, general flow patterns as well as changes in the direction of progression are well reproduced. The run-out distances are determined using empirically based models and suit well the case studies presented