ABSTRACT
Left-Right (LR) asymmetry of the nervous system is widespread across animals and is thought to be important for cognition and behaviour. But in contrast to visceral organ asymmetry, the genetic basis and function of brain laterality remain only poorly characterized. In this study, we performed RNAi screening to identify genes controlling brain asymmetry in Drosophila. We found that the conserved NetrinB (NetB) pathway is required for a small group of bilateral neurons to project asymmetrically into a pair of neuropils (Asymmetrical Bodies, AB) in the central brain in both sexes. While neurons project unilaterally into the right AB in wild-type flies, netB mutants show a bilateral projection phenotype and hence lose asymmetry. Developmental time course analysis reveals an initially bilateral connectivity, eventually resolving into a right asymmetrical circuit during metamorphosis, with the NetB pathway being required just prior symmetry breaking. We show using unilateral clonal analysis that netB activity is required specifically on the right side for neurons to innervate the right AB. We finally show that loss of NetB pathway activity leads to specific alteration of long-term memory, providing a functional link between asymmetrical circuitry determined by NetB and animal cognitive functions.
Subject(s)
Drosophila Proteins , Drosophila , Animals , Male , Female , Drosophila/metabolism , Brain/metabolism , Drosophila Proteins/metabolism , Neuropil/metabolism , Body Patterning/genetics , Functional Laterality/physiology , Nerve Growth Factors/metabolismABSTRACT
The emergence of asymmetry from an initially symmetrical state is a universal transition in nature. Living organisms show asymmetries at the molecular, cellular, tissular, and organismal level. However, whether and how multilevel asymmetries are related remains unclear. In this study, we show that Drosophila myosin 1D (Myo1D) and myosin 1C (Myo1C) are sufficient to generate de novo directional twisting of cells, single organs, or the whole body in opposite directions. Directionality lies in the myosins' motor domain and is swappable between Myo1D and Myo1C. In addition, Myo1D drives gliding of actin filaments in circular, counterclockwise paths in vitro. Altogether, our results reveal the molecular motor Myo1D as a chiral determinant that is sufficient to break symmetry at all biological scales through chiral interaction with the actin cytoskeleton.
Subject(s)
Actin Cytoskeleton/chemistry , Drosophila Proteins/chemistry , Models, Molecular , Myosin Type I/chemistry , Animals , Drosophila Proteins/antagonists & inhibitors , Drosophila melanogaster/growth & development , Isomerism , Larva , Myosin Type I/antagonists & inhibitors , Myosin Type V/chemistry , Protein DomainsABSTRACT
Border Cells in the Drosophila ovaries are a useful genetic model for understanding the molecular events underlying epithelial cell motility. During stage 9 of egg chamber development they detach from neighboring stretched cells and migrate between the nurse cells to reach the oocyte. RNAi screening allowed us to identify the dapc1 gene as being critical in this process. Clonal and live analysis showed a requirement of dapc1 in both outer border cells and contacting stretched cells for delamination. This mutant phenotype was rescued by dapc1 or dapc2 expression. Loss of dapc1 function was associated with an abnormal lasting accumulation of ß-catenin/Armadillo and E-cadherin at the boundary between migrating border and stretched cells. Moreover, ß-catenin/armadillo or E-cadherin downregulation rescued the dapc1 loss of function phenotype. Altogether these results indicate that Drosophila Apc1 is required for dynamic remodeling of ß-catenin/Armadillo and E-cadherin adhesive complexes between outer border cells and stretched cells regulating proper delamination and invasion of migrating epithelial clusters.
Subject(s)
Drosophila Proteins/metabolism , Drosophila melanogaster/metabolism , Epithelial Cells/metabolism , Ovary/metabolism , Tumor Suppressor Proteins/metabolism , Animals , Animals, Genetically Modified , Armadillo Domain Proteins/genetics , Armadillo Domain Proteins/metabolism , Cadherins/genetics , Cadherins/metabolism , Cell Adhesion , Cell Movement , Cytoskeletal Proteins , Drosophila Proteins/genetics , Drosophila melanogaster/cytology , Drosophila melanogaster/genetics , Epithelial Cells/cytology , Female , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , Immunohistochemistry , Microscopy, Confocal , Mutation , Oocytes/cytology , Oocytes/metabolism , Ovary/cytology , RNA Interference , Tumor Suppressor Proteins/genetics , beta Catenin/genetics , beta Catenin/metabolismABSTRACT
A method for the preconcentration and speciation of chromium was developed. After formation of an anionic compound with ethylenediaminetetraacetic acid (CrY(-)), Cr (VI) and Cr (III) are retained on a strong anionic phase (SAX) and controlled elution with 0.5 M NaCl permits their speciation. The retention and elution conditions were optimised, and interferences due to the presence of other ions such as Mg(II), Mn(II), Sn(II), Fe(III), Ba(II), Al(III), Ca(II), chloride, iodine, bromide, fluoride, sulphate, phosphate, bicarbonate and nitrate were studied. The detection limits were 0.4 mug l(-1) and 1.1 mug l(-1) for Cr(III) and Cr(VI), respectively, and reproducibility was 9%. The results obtained for speciation of chromium by the proposed method in wastewaters are in agreement with the values obtained by a reference method for a 95% confidence level.
