Characterization of rho GTPase family homologues in Drosophila melanogaster: overexpressing Rho1 in retinal cells causes a late developmental defect.

Abstract

The rho family of GTPases has been implicated in regulating changes in cell morphology in response to extracellular signals. We have cloned three widely expressed members of this family from Drosophila melanogaster; a rho homologue (Rho1) and two rac homologues (Rac1 and Rac2). Flies harbouring a Rho1 transgene that is specifically expressed in the eye exhibit a dramatic dose dependent disruption of normal eye development. Flies bearing at least two copies of the transgene display a severe rough eye phenotype characterized by missing secondary and tertiary pigment cells, a substantial reduction in the number of photoreceptor cells and a grossly abnormal morphology of the rhabdomeres. Cell fate determination in the imaginal disc occurs normally and abnormalities become manifest late in pupariation, coincident with the phase when the cells undergo major morphological changes. This phenotype is modified by mutations at several other loci that have been implicated in signal transduction, but not by mutations in ras pathway components.

Roles of Type I Myosins in Drosophila Handedness

“…Rho1 and Rac1, small GTPases encoded by Drosophila RhoA and Rac1, respectively, are known to control the organization of actin filament. 18,19 The overexpression of a dominant-negative form of Rho1 or Rac1 in the hindgut epithelium caused LR defects in the hindgut (Table 1), as did the overexpression of Moe-GFP, an actin-binding domain of Moesin fused with GFP (Table 1). For reviews on the roles of the actin cytoskeleton in LR asymmetric development in Drosophila, see references.…”

Ectopic expression of constitutively activated Ral GTPase inhibits cell shape changes during Drosophila eye development

“…Immunohistochemistry was carried out essentially as described (Tomlinson and Ready, 1987). Phalloidin staining was performed using the method of Hariharan et al (1995).…”

“…The fruit¯y, Drosophila melanogaster, provides a unique system to investigate the roles of the small GTP-binding proteins in development. The Drosophila homologues of RhoA, Rac1, Rac2 and CDC42 have been identi®ed and implicated in several developmental processes including eye morphogenesis, axonal outgrowth, dorsal closure and hair development (Luo et al, 1994;Hariharan et al, 1995;Harden et al, 1995;Eaton et al, 1996;Barret et al, 1997;Strutt et al, 1997).…”

Cleavage and nuclear translocation of the caspase 3 substrate Rho GDP-dissociation inhibitor, D4-GDI, during apoptosis

“…This protein functions to keep the Rho protein in its GDP-bound inactive state. The Rho family of small GTPases including Rho, Rac, and Cdc42, have been shown to regulate many cellular processes such as the assembly of the actin cytoskeleton and focal adhesions, 14 oxidant production in leukocytes, and the stress response through activation of cJun N-terminal kinase and p38 mpk2 . 15 Previously D4-GDI has been reported to be cleaved at aspartate 19 by caspase 3 during apoptosis in Jurkat Tcells induced with anti-Fas antibody, overexpression of Bax, and staurosporine, 16,17 and in BL60 Burkitt lymphoma cells induced with anti-IgM.…”