We have identified a novel Drosophila gene, DRacGAP, which behaves as a negative regulator of Ρ-family GTPases DRac1 and DCdc42. Reduced function of DRacGAP or increased expression of DRac1 in the wing imaginal disc cause similar effects on vein and sensory organ development and cell proliferation. These effects result from enhanced activity of the EGFR/Ras signalling pathway. We find that in the wing disc, DRac1 enhances EGFR/Ras-dependent activation of MAP Kinase in the prospective veins. Interestingly, DRacGAP expression is negatively regulated by the EGFR/Ras pathway in these regions. During vein formation, local DRacGAP repression would ensure maximal activity of Rac and, in turn, of Ras pathways in vein territories. Additionally, maximal expression of DRacGAP at the vein/intervein boundaries would help to refine the width of the veins. Hence, control of DRacGAP expression by the EGFR/Ras pathway is a previously undescribed feedback mechanism modulating the intensity and/or duration of its signalling during Drosophila development.

REFERENCES

REFERENCES
Agnel
M.
,
Röder
L.
,
Vola
C.
,
Griffin-Shea
R.
(
1992
)
A Drosophila rotund transcript expressed during spermatogenesis and imaginal disc morphogenesis encodes a protein which is similar to human Rac GTPase-activating (racGAP) proteins.
Mol. Cell Biol
12
,
5111
5122
Ahmed
S.
,
Lee
J.
,
Wen
L.P.
,
Zhao
Z.
,
Ho
J.
,
Best
A.
,
Kozma
R.
,
Lim
L.
(
1994
)
Breakpoint cluster region gene product-related domain of n -chimaerin.
J. Biol. Chem
269
,
17642
17648
Aspenström
P.
(
1999
)
Effectors for Rho GTPases.
Curr. Opin. Cell Biol
11
,
95
102
Baker
N. E.
,
Rubin
G. M.
(
1992
)
Ellipse mutations in the Drosophila homologue of the EGF receptor affect pattern formation, cell division, and cell death in eye imaginal discs.
Dev. Biol
150
,
381
396
Barrett
K.
,
Leptin
M.
,
Settleman
J.
(
1997
)
The Rho GTPase and a putative RhoGEF mediate a signaling pathway for the cell shape changes in Drosophila gastrulation.
Cell
91
,
905
915
Blair
S. S.
(
1992
)
engrailed expression in the anterior lineage compartmentof the developing wing blade of Drosophila.
Development
115
,
21
33
Boguski
M. S.
,
McCormick
F.
(
1993
)
Proteins regulating Ras and its relatives.
Nature
366
,
643
654
Bourne
H. R.
,
Sanders
D. A.
,
McCormick
F.
(
1990
)
The GTPase superfamily: a conserved switch for diverse cell functions.
Nature
348
,
125
132
Brand
A. H.
,
Perrimon
N.
(
1993
)
Targeted gene expression as a meansof altering cell fates and generating dominant phenotypes.
Development
118
,
401
415
Brunner
D.
,
Oellers
N.
,
Szabad
J.
,
Biggs
W. H.
III
,
Zipursky
S. L.
,
Hafen
E.
(
1994
)
A gain-of-function mutation in Drosophila MAP kinase activates multiple receptor tyrosine kinase signalling pathways.
Cell
76
,
875
888
Clifford
R. J.
,
Schupbach
T.
(
1989
)
Coordinately and differentially mutable activities of torpedo, the Drosophila melanogaster homolog of the vertebrate EGF receptor gene.
Genetics
123
,
771
787
Conlon
I.
,
Raff
M.
(
1999
)
Size control in animal development.
Cell
96
,
235
244
Cubas
P.
,
de Celis
J. F.
,
Campuzano
S.
,
Modolell
J.
(
1991
)
Proneural clusters of achaete-scute expression and the generation of sensory organs in the Drosophila imaginal wing disc.
Genes Dev
5
,
996
1008
de Celis
J. F.
(
1998
)
Positioning and differentiation of veins in the Drosophila wing.
Int. J. Dev. Biol
42
,
335
343
de Nooij
J. C.
,
Hariharan
I. K.
(
1995
)
Uncoupling cell fate determination from patterned cell division in the Drosophila eye.
Science
270
,
983
985
Devereux
J.
,
Haeverli
P.
,
Smithies
O.
(
1984
)
A comprehensive set of sequence analysis programs for the VAX.
Nuc. Acids Res
12
,
387
395
Díaz-Benjumea
F. J.
,
García-Bellido
A.
(
1990
)
Behaviour of cells mutant for an EGF receptor homologue of Drosophila in genetic mosaics.
Proc. R. Soc. Lond
242
,
36
44
Díaz-Benjumea
F. J.
,
Hafen
E.
(
1994
)
The sevenless signalling cassette mediates Drosophila EGF receptor function during epidermal development.
Development
120
,
569
578
Dieckmann
D.
,
Brill
S.
,
Garrett
M. D.
,
Totti
N.
,
Hsuan
J.
,
Monfries
C.
,
Hall
C.
,
Lim
L.
,
Hall
A.
(
1991
)
Bcr encodes a GTPase activating protein for p21Rac.
Nature
351
,
400
402
Downward
J.
(
1997
)
Routine role for Ras.
Curr. Biol
7
,
258
–.
Downward
J.
(
1998
)
Ras signalling and apoptosis.
Curr. Opin. Genet. Dev
8
,
49
54
Eaton
S.
(
1997
)
Planar polarization of Drosophila and vertebrate epithelia.
Curr. Opin. Cell Biol
9
,
860
866
Eaton
S.
,
Wepf
R.
,
Simons
K.
(
1996
)
Roles of Rac1 and Cdc42 in planar polarization and hair outgrowth in the wing of Drosophila.
J. Cell Biol
135
,
1277
1289
Edgar
B. A.
,
O'Farrell
P. H.
(
1990
)
The three postblastoderm cell cycles of Drosophila embryogenesis are regulated in G2 by string.
Cell
62
,
469
480
Fehon
R. G.
,
Oren
T.
,
LaJeunesse
D. R.
,
Melby
T. E.
,
McCartney
B. M.
(
1997
)
Isolation of mutations in the Drosophila homologues of the human Neurofibromatosis 2 and yeast CDC42 genes using a simple and efficient reverse-genetic method.
Genetics
146
,
245
252
Freeman
M.
,
Klämbt
C.
,
Goodman
C. S.
,
Rubin
G. M.
(
1992
)
The argos gene encodes a diffusible factor that regulates cell fate decisions in the Drosophila eye.
Cell
69
,
963
975
Frost
J. A.
,
Steen
H.
,
Shapiro
P.
,
Lewis
T.
,
Ahn
N.
,
Shaw
P. E.
,
Cobb
M. H.
(
1997
)
Cross-cascade activation of ERKs and ternary complex factors by Rho family proteins.
EMBO J
16
,
6426
6438
Gabay
L.
,
Seger
R.
,
Shilo
B. Z.
(
1997
)
In situ activation pattern of Drosophila EGF receptor pathway during development.
Science
277
,
1103
1106
Guichard
A.
,
Bergeret
E.
,
Griffin-Shea
R.
(
1997
)
Overexpression of RnRacGAP in Drosophila melanogaster deregulates cytoskeletal organisation in cellularising embryos and induces discrete imaginal phenotypes.
Mech. Dev
61
,
49
62
Hackel
P. O.
,
Zwick
E.
,
Prenzel
N.
,
Ullrich
A.
(
1999
)
Epidermal growth factor receptors: critical mediators of multiple receptor pathways.
Curr. Opin. Cell Biol
11
,
184
189
Häcker
U.
,
Perrimon
N.
(
1998
)
DRhoGEF2 encodes a member of the Dbl family of oncogenes and controls cell shape changes during gastrulation in Drosophila.
Genes Dev
12
,
274
284
Hall
A.
(
1998
)
Rho GTPases and the actin cytoskeleton.
Science
279
,
509
514
Harden
N.
,
Lee
J.
,
Loh
H. Y.
,
Ong
Y. M.
,
Tan
I.
,
Leung
T.
,
Manser
E.
,
Lim
L.
(
1996
)
A Drosophila homolog of the Rac-and Cdc42-activated serine/threonine kinase PAK is a potential focal adhesion and focal complex protein that colocalizes with dynamic actin structures.
Mol. Cell. Biol
16
,
1896
1908
Hay
B. A.
,
Wolff
T.
,
Rubin
G. M.
(
1994
)
Expression of baculovirus P35 prevents cell death in Drosophila.
Development
120
,
2121
2129
Hemsley
A.
,
Arnheim
N.
,
Toney
M.
,
Cortopassi
G.
,
Galas
D.
(
1989
)
A simple method for site-directed mutagenesis using the polymerase chain reaction.
Nucl. Acid Res
17
,
6545
6551
Hing
H.
,
Xiao
J.
,
Harden
N.
,
Lim
L.
,
Zipursky
S. L.
(
1999
)
Pak functions downstream of Dock to regulate photoreceptor axon guidance in Drosophila.
Cell
97
,
853
863
Karim
F. D.
,
Rubin
G. M.
(
1998
)
Ectopic expression of activated Ras 1 induces hyperplastic growth and increased cell death in Drosophila imaginal tissues.
Development
125
,
1
9
King
A. J.
,
Sun
H.
,
Diaz
B.
,
Barnard
D.
,
Miao
W.
,
Bagrodia
S.
,
Marshall
M. S.
(
1998
)
The protein kinase Pak3 positively regulates Raf-1 activity through phosphorylation of serine 338.
Nature
396
,
180
183
Knoblich
J. A.
,
Sauer
K.
,
Jones
L.
,
Richardson
H.
,
Saint
R.
,
Lehner
C. F.
(
1994
)
Cyclin E controls S phase progression and its down-regulation during Drosophila embryogenesis is required for the arrest of cell proliferation.
Cell
77
,
107
120
Lamarche
N.
,
Hall
A.
(
1994
)
Gaps for Rho-related GTPases.
Trends Genet
10
,
436
440
Lu
Y.
,
Settleman
J.
(
1999
)
The Drosophila Pkn kinase is a Rho/Rac effector target required for dorsal closure during embryogenesis.
Genes Dev
13
,
1168
1180
Luo
L.
,
Jan
L. Y.
,
Jan
Y. N.
(
1997
)
Rho family small GTP-binding proteins in growth cone signalling.
Curr. Opin. Neurobiol
7
,
81
86
Luo
L.
,
Liao
Y. J.
,
Jan
L. Y.
,
Jan
Y. N.
(
1994
)
Distinct morphogenetic functions of similar small GTPases: Drosophila Drac1 is involved in axonal outgrowth and myoblast fusion.
Genes Dev
8
,
1787
1802
Magie
C. R.
,
Meyer
M. R.
,
Gorsuch
M. S.
,
Parkhurst
S. M.
(
1999
)
Mutations in the Rho1 small GTPase disrupt morphogenesis and segmentation during early Drosophila development.
Development
126
,
5353
5364
Marshall
C. J.
(
1995
)
Specificity of receptor tyrosine kinase signaling: Transient versus sustained extracellular signal-regulated kinase activation.
Cell
80
,
179
185
Martín-Blanco
E.
(
1998
)
Regulatory control of signal transduction during morphogenesis in Drosophila.
Int. J. Dev. Biol
42
,
363
368
Martín-Blanco
E.
,
Roch
F. E. N.
,
Baonza
A.
,
Duffy
J. B.
,
Perrimon
N.
(
1999
)
A temporal switch in DER signaling controls the specification and differentiation of veins and interveins in the Drosophila wing.
Development
126
,
5739
5747
Milán
M.
,
Campuzano
S.
,
García-Bellido
A.
(
1997
)
Developmental parameters of cell death in the wing disc of Drosophila.
Proc. Natl. Acad. Sci. USA
94
,
5691
5696
Montell
D. J.
(
1999
)
The genetics of cell migration in Drosophila melanogaster and Caenorhabditis elegans development.
Development
126
,
3035
3046
Neufeld
T. P.
,
de la Cruz
A. F. A.
,
Johnston
L. A.
,
Edgar
B. A.
(
1998
)
Coordination of growth and cell division in the Drosophila wing.
Cell
93
,
1183
1193
Noselli
S.
,
Agnes
F.
(
1999
)
Roles of the JNK signaling pathway in Drosophila morphogenesis.
Curr. Opin. Genet. Dev
9
,
466
472
Olson
M. F.
,
Paterson
H. F.
,
Marshall
C. J.
(
1998
)
Signals from Ras and Rho GTPases interact to regulate expression of p21Waf1/Cip1.
Nature
394
,
295
299
Perrimon
N.
,
McMahon
A. P.
(
1999
)
Negative feedback mechanisms and their roles during pattern formation.
Cell
97
,
13
16
Prokopenko
S. N.
,
Brumby
A.
,
O'Keefe
L.
,
Prior
L.
,
He
Y.
,
Saint
R.
,
Bellen
H. J.
(
1999
)
A putative exchange factor for Rho1 GTPase is required for the initiation of cytokinesis in Drosophila.
Genes Dev
13
,
2301
2314
Rommel
C.
,
Hafen
E.
(
1998
)
Ras—a versatile cellular switch.
Curr. Opin. Genet. Dev
8
,
412
418
Scheffzek
K.
,
Ahmadian
M. R.
,
Wittinghofer
A.
(
1998
)
GTPase-activating proteins: helping hands to complement an active site.
Trends Biochem. Sci
23
,
257
262
Schnepp
B.
,
Grumbling
G.
,
Donaldson
T.
,
Simcox
A.
(
1996
)
Vein is a novel component in the Drosophila epidermal growth factor receptor pathway with similarity to the neuregulins.
Genes Dev
10
,
2302
2313
Schwartz
M. A.
,
Baron
V.
(
1999
)
Interactions between mitogenic stimuli, or, a thousand and one connections.
Curr. Opin. Cell Biol
11
,
197
202
Schweitzer
R.
,
Howes
R.
,
Smith
R.
,
Shilo
B. Z.
,
Freeman
M.
(
1995
)
Inhibition of Drosophila EGF receptor activation by the secreted protein Argos.
Nature
376
,
699
702
Sewing
A.
,
Wiseman
B.
,
Lloyd
A. C.
,
Land
H.
(
1997
)
High-intensity Raf signal causes cell cycle arrest mediated by p21Cip1.
Mol. Cell. Biol
17
,
5588
5597
Simcox
A.
(
1997
)
Differential requirement for EGF-like ligands in Drosophila wing development.
Mech. Dev
62
,
41
50
Simcox
A. A.
,
Grumbling
G.
,
Schnepp
B.
,
Bennington-Mathias
C.
,
Hersperger
E.
,
Shearn
A.
(
1996
)
Molecular, phenotypic, and expression analysis of vein, a gene required for growth of the Drosophila wing disc.
Dev. Biol
177
,
475
489
Simpson
P.
(
1979
)
Parameters of cell competition in the compartments of the wing disc of Drosophila.
Dev. Biol
69
,
182
193
Sone
M.
,
Hoshino
M.
,
Suzuki
E.
,
Kuroda
S.
,
Kaibuchi
K.
,
Nakagoshi
H.
,
Saigo
K.
,
Nabeshima
Y.
,
Hama
C.
(
1997
)
Still life, a protein in synaptic terminals of Drosophila homologous to GDP-GTP exchangers.
Science
275
,
543
547
Sotillos
S.
,
Roch
F.
,
Campuzano
S.
(
1997
)
The metalloprotease-disintegrin Kuzbanian participates in Notch activation during growth andpatterning of the Drosophila imaginal discs.
Development
124
,
4769
4779
Sternberg
P. W.
,
Alberola-Ila
J.
(
1998
)
Conspiracy theory: RAS and RAF do not act alone.
Cell
95
,
447
450
Struhl
G.
,
Basler
K.
(
1993
)
Organizing activity of wingless protein in Drosophila.
Cell
72
,
527
540
Strutt
D. I.
,
Weber
U.
,
Mlodzik
M.
(
1997
)
The role of RhoA in tissue polarity and Frizzled signaling.
Nature
387
,
292
295
Sturtevant
M. A.
,
Roark
M.
,
Bier
E.
(
1993
)
The Drosophila rhomboid gene mediates the localized formation of wing veins and interacts genetically with components of the EGF-R signaling pathway.
Genes Dev
7
,
961
973
Van Aelst
L.
,
D'Souza-Schorey
C.
(
1997
)
Rho GTPases and signaling networks.
Genes Dev
11
,
2295
2322
Wasserman
J. D.
,
Freeman
M.
(
1998
)
An autoregulatory cascade of EGF receptor signaling patterns the Drosophila egg.
Cell
95
,
355
364
Weigmann
K.
,
Cohen
S. M.
,
Lehner
C. F.
(
1997
)
Cell cycle progression, growth and patterning in imaginal discs despite inhibition of cell division after inactivation of Drosophila Cdc2 kinase.
Development
124
,
3555
3563
Woods
D.
,
Parry
D.
,
Cherwinski
H.
,
Bosch
E.
,
Lees
R.
,
McMahon
M.
(
1997
)
Raf-induced proliferation or cell cycle arrest is determined by the level of Raf activity with arrest mediated by p21Cip1.
Mol. Cell. Biol
17
,
5598
5611
Wooltorton
E. J.
,
Haliotis
T.
,
Mueller
C. R.
(
1999
)
Identification and characterization of a transcript for a novel Rac GTPase-activating protein in terminally differentiating 3T3-L1 adipocytes.
DNA Cell Biol
18
,
265
273
Yuan
S.
,
MIller
D. W.
,
Barnett
G. H.
,
Hahn
J. F.
,
Williams
B. R.
(
1995
)
Identification and characterization of human beta 2-chimaerin: association with malignant transformation in astrocytoma.
Cancer Res
55
,
3456
3461
This content is only available via PDF.