Sharp boundaries of Dpp signalling trigger local cell death required for Drosophila leg morphogenesis

Article available at http://dx.doi.org/10.1038/ncb1518Morphogens are secreted signalling molecules that govern many developmental processes1. In the Drosophila wing disc, the transforming growth factor (TGF) homologue Decapentaplegic (Dpp) forms a smooth gradient and specifies cell fate by conferring a defined value of morphogen activity. Thus, neighbouring cells have similar amounts of Dpp protein, and if a sharp discontinuity in Dpp activity is generated between these cells, Jun kinase (JNK)-dependent apoptosis is triggered to restore graded positional information2, 3. To date, it has been assumed that this apoptotic process is only activated when normal signalling is distorted. However, we now show that a similar process occurs during normal development: rupture in Dpp activity occurs during normal segmentation of the distal legs of Drosophila. This sharp boundary of Dpp signalling, independently of the absolute level of Dpp activity, induces a JNK—reaper-dependent apoptosis required for the morphogenesis of a particular structure of the leg, the joint. Our results show that Dpp could induce a developmental programme not only in a concentration dependent manner, but also by the creation of a sharp boundary of Dpp activity. Furthermore, the same process could be used either to restore a normal pattern in response to artificial disturbance or to direct a morphogenetic process.This work has been supported by grants from the Dirección General de Investigación Científica y Técnica (BMC 2002-00300), the Comunidad Autónoma de Madrid (08.1/0031/2001.1 and GR/SAL/0147/2004) and an Institutional Grant from the Fundación Ramón Areces. C.M. is a recipient of a Formación del Personal Universitario (F.P.U.) fellowship from the Ministerio de Educación y Ciencia.Peer reviewe

Comparative analysis of somitogenesis related genes of the hairy/Enhancer of split class in Fugu and zebrafish

BACKGROUND: Members of a class of bHLH transcription factors, namely the hairy (h), Enhancer of split (E(spl)) and hairy-related with YRPW motif (hey) (h/E(spl)/hey) genes are involved in vertebrate somitogenesis and some of them show cycling expression. By sequence comparison, identified orthologues of cycling somitogenesis genes from higher vertebrates do not show an appropriate expression pattern in zebrafish. The zebrafish genomic sequence is not available yet but the genome of Fugu rubripes was recently published. To allow comparative analysis, the currently known Her proteins from zebrafish were used to screen the genomic sequence database of Fugu rubripes. RESULTS: 20 h/E(spl)/hey-related genes were identified in Fugu, which is twice the number of corresponding zebrafish genes known so far. A novel class of c-Hairy proteins was identified in the genomes of Fugu and Tetraodon. A screen of the human genome database with the Fugu proteins yielded 10 h/E(spl)/hey-related genes. By analysing the upstream sequences of the c-hairy class genes in zebrafish, Fugu and Tetraodon highly similar sequence stretches were identified that harbour Suppressor of hairless paired binding sites (SPS). This motif was also discovered in the upstream sequences of the her1 gene in the examined fish species. Here, the Su(h) sites are separated by longer intervening sequences. CONCLUSIONS: Our study indicates that not all her homologues in zebrafish have been isolated. Comparison to the human genome suggests a selective duplication of h/E(spl) genes in pufferfish or loss of members of these genes during evolution to the human lineage

Presenilin Controls CBP Levels in the Adult Drosophila Central Nervous System

Background: Dominant mutations in both human Presenilin (Psn) genes have been correlated with the formation of amyloid plaques and development of familial early-onset Alzheimer’s disease (AD). However, a definitive mechanism whereby plaque formation causes the pathology of familial and sporadic forms of AD has remained elusive. Recent discoveries of several substrates for Psn protease activity have sparked alternative hypotheses for the pathophysiology underlying AD. CBP (CREB-binding protein) is a haplo-insufficient transcriptional co-activator with histone acetly-transferase (HAT) activity that has been proposed to be a downstream target of Psn signaling. Individuals with altered CBP have cognitive deficits that have been linked to several neurological disorders. Methodology/Principal Findings: Using a transgenic RNA-interference strategy to selectively silence CBP, Psn, and Notch in adult Drosophila, we provide evidence for the first time that Psn is required for normal CBP levels and for maintaining specific global acetylations at lysine 8 of histone 4 (H4K8ac) in the central nervous system (CNS). In addition, flies conditionally compromised for the adult-expression of CBP display an altered geotaxis behavior that may reflect a neurological defect. Conclusions/Significance: Our data support a model in which Psn regulates CBP levels in the adult fly brain in a manner that is independent of Notch signaling. Although we do not understand the molecular mechanism underlying th

The Gene Regulatory Cascade Linking Proneural Specification with Differentiation in Drosophila Sensory Neurons

Temporal expression profiling of sensory precursor cells reveals how the atonal proneural transcription factor regulates a specialized neuronal differentiation pathway

Robust Target Gene Discovery through Transcriptome Perturbations and Genome-Wide Enhancer Predictions in Drosophila Uncovers a Regulatory Basis for Sensory Specification

CisTarget X is a novel computational method that accurately predicts Atonal governed regulatory networks in the retina of the fruit fly

Biological lattices in fast self-repair mechanisms in plants and the development of bio-inspired self-healing polymers

Polymers are often used in fields of application with high mechanical loads. Thereby, micro-cracks, which can exist in every component, may grow up to overcritical lengths. Thus, components may fail even far below the maximum critical load. Equipping these components with self-healing capabilities is a smart way of preventing them from failure, as healing the micro-cracks may inhibit or at least decelerate crack expansion. The ability of self-healing is common in many plant species. For example, the initial tensile strength of uninjured bark of Ficus benjamina is partly restored after injury by self-repair due to the secretion and coagulation of latex. Several tests such as infrared spectroscopy and analyses of the duration and pressure dependency of latex coagulation were conducted, as shown in a case study for F. benjamina. These tests will also be used in a standardized way for a comparison of the coagulation mechanisms of different latex-bearing plants. The biological self-healing mechanisms will serve as role models for a transfer into bio-inspired technical self-healing materials

Analysis of stress gradients in physical vapour deposition multilayers by X-ray diffraction at fixed depth intervals

The objective of this article is to develop and apply a model for the design and evaluation of X-ray diffraction experiments to measure phase-specific residual stress profiles in multilayer systems. Using synchrotron radiation and angle-dispersive diffraction, the stress measurements are performed on the basis of the sin2[psi] method. Instead of the traditional [Omega] or [chi] mode, the experiments are carried out by a simultaneous variation of the goniometer angles [chi], [Omega] and [varphi]G to ensure that the penetration and information depth and the measuring direction [varphi] remain unchanged when the polar angle [psi] is varied. The applicability of this measuring and evaluation strategy is demonstrated by the example of a multilayer system consisting of Ti and TiAlN layers, alternately deposited on a steel substrate by means of physical vapour deposition