Two transcripts from the rotund region of Drosophila show similar positional specificities in imaginal disc tissues.

Abstract

The rotund (rn) mutation in Drosophila is unique in that its phenotype is limited to the deletion of specific distal parts, though not the extremities, of all adult appendages. We have cloned the rn gene, located at cytogenetic position 84D3,4, by chromosomal walking. The functional rn unit, defined genetically by the localization of 13 noncomplementing rn alleles, covers -50 kb of DNA. Despite different developmental profiles, two transcript size classes (1.7 and 5.3 kb) from this region show an indistinguishable pattern of spatial expression in the imaginal discs at the white pupa stage. There is a high correlation between the specificity of the mutant phenotype and the accumulation of transcripts in the presumptive distal regions of the cuticleforming epithelial cells of the affected discs; it is, in fact, the first gene reported whose expression is localized with respect to the proximo distal-forming axis. For both transcripts, we have also found, uniquely in the wing disc, expression limited to the anterior region of the mesodermally derived adepithelial cells, which contribute to the muscles of the thorax. The imaginal discs of Drosophila melanogaster are the primordia of the adult cuticular structures of the head, thorax, genitalia, and analia. The discs form as invaginations of the ectoderm from cells set aside at the blastoderm stage. They grow during the larval stages and then evaginate and differentiate during pupation. Each disc gives rise to a specific part of the adult. Of the 19 imaginal discs, 14 give rise to structures that we consider appendages on the basis of their morphology: the wings, legs, halteres, antennae, and the proboscis. Several lines of evidence suggest that the mechanisms of pattern formation in these discs are similar. Their fate maps at the third-instar larval stage show that they are organized according to a concentric plan, the center of the disc giving rise to the distal tip of the appendage and the more peripheral parts to progressively more proximal structures. (For a review of disc development, see Bryant 1978). Finally, the combined results from studies of cell sorting {Garcia-Bellido 1966; Tobler 1966), disc regeneration (Haynie 19821, and several homeotic mutants (Postlethwait and Schneiderman 19711 suggest that the same signals are used in all these discs to specify a cell's relative position, a conclusion consistent with Wolpert's theory of positional information (1969, 1971).The segmentation of the embryo of Drosophila is established by a stepwise process that subdivides the anteroposterior axis into segmental units within which ~Corresponding author. pattem is subsequently formed (Scott and O'Farrell 1986}. In the discs, both the polar coordinate [French et al. 19761 and secondary embryonic field (Meinhardt 1983} models propose that pattern is ultimately elaborated along the proximo-distal axis. Genetic evidence supporting this hypothesis is provided by the decapentaplegic (dpp} (Spencer et al. 19821 and wingless (wg) (Baker 19881 hypomorphic mutations. Mutati...

A screen for modifiers of RacGAP(84C) gain-of-function in theDrosophilaeye revealed the LIM kinase Cdi/TESK1 as a downstream effector of Rac1 during spermatogenesis

“…The EP lines presenting a strong eye phenotype with GMRGal4 were discarded whereas those presenting a moderate eye phenotype with GMRGal4, and a strong enhancement or lethality with GG17, were crossed to a GMRGal4; rn 20 /TM3,Sb strain. The deficiency rn 20 maps to 84C and deletes the entire RacGAP(84C) transcription unit and overlapping genes including roe and rn (Agnel et al, 1989;St Pierre et al, 2002).…”

RotundRacGAP Functions with Ras during Spermatogenesis and Retinal Differentiation in Drosophila melanogaster

“…Data in this paper are shown for the rn 20 mutation, which was chosen as representative for extended analyses in transgenic rescue experiments. The original rn 20 mutation is described in Agnel et al (1): the proximal breakpoint lies between Antennapedia (27) and the glucose dehydrogenase gene (10); the distal breakpoint does not include the cluster of four male-sterile genes, Mst84Da, Mst84Db, Mst84Dc, and Mst84Dd, described previously (31). To control for possible effects of genetic background on the sterility of flies carrying the original rn 20 red e chromosome, the mutant strain was outcrossed over seven generations to a Pinsertion line, e(Pc)84DE, obtained from a w 1118 isogenic strain carrying an insertion close to rn (16).…”

“…The GTPase-activating proteins (GAPs) have been defined in biochemical and cell culture studies as negative regulators of these proteins (30), stimulating their intrinsic GTPase activity, thereby leading to GDP binding and downregulation (7). We previously isolated a GAP gene, rotundRacGAP (rnRacGAP), from Drosophila melanogaster (1). The protein product, RotundRacGAP (RnRacGAP), shows high sequence similarity in C-terminal regions (3) to the RacGAP protein Bcr (13), the N-chimaerins (24), and a remarkable overall similarity (60%) with MgcRacGAP, the product of the human gene male germ cell RacGAP (52).…”

Bowl is required downstream of Notch for elaboration of distal limb patterning

“…Subsequent patterning involves interactions between the factors expressed in these early territories. For example, several genes are required for the development of the tarsus, including rotund and bric-a-brac (Kerridge and Thomas-Cavallin, 1988;Agnel et al, 1989;Godt et al, 1993;Chu et al, 2002;Couderc et al, 2002;Galindo et al, 2002;St Pierre et al, 2002). Expression of these genes is promoted by Dll and restricted by the combined activities of Dac proximally and a gradient of epidermalgrowth-factor-receptor signalling distally (Campbell and Tomlinson, 1998;Campbell, 2002;Galindo et al, 2002).…”