The combgap locus, first described by C. B. Bridges in 1925, is a gene required for proper anteroposterior pattern formation in the limbs of Drosophila melanogaster. The development of the anteroposterior axis of fly limbs is initiated by hedgehog signaling from cells of the posterior half to cells of the anterior half of the limb primordium. Hedgehog signaling requires the anterior-specific expression of the gene cubitus interruptus to establish posterior-specific hedgehog secretion and anterior-specific competence to respond to hedgehog. We have cloned combgap and find that it encodes a chromosomal protein with 11 C(2)H(2) zinc fingers. Limb defects found in combgap mutants consist of either loss or duplication of pattern elements in the anteroposterior axis and can be explained through the inappropriate expression of cubitus interruptus and its downstream target genes. In combgap mutants, cubitus interruptus is ectopically expressed in the posterior compartments of wing imaginal discs and is downregulated in the anterior compartment of legs, wings and antennae. We are able to rescue anterior compartment combgap phenotypes by expressing additional cubitus interruptus using the Gal4/UAS system. Dominant alleles of cubitus interruptus, which result in posterior expression, phenocopy combgap posterior compartment phenotypes. Finally, we find that the combgap protein binds to polytene chromosomes at many sites including the cubitus interruptus locus, suggesting that it could be a direct regulator of cubitus interruptus transcription.

REFERENCES

Aza-Blanc
P.
,
Kornberg
T. B.
(
1999
)
Ci: a complex transducer of the hedgehog signal.
Trends Genet
15
,
458
462
Aza-Blanc
P.
,
Ramirez-Weber
F. A.
,
Laget
M. P.
,
Schwartz
C.
,
Kornberg
T. B.
(
1997
)
Proteolysis that is inhibited by hedgehog targets Cubitus interruptus protein to the nucleus and converts it to a repressor.
Cell
89
,
1043
1053
Basler
K.
,
Struhl
G.
(
1994
)
Compartment boundaries and the control of Drosophila limb pattern by hedgehog protein.
Nature
368
,
208
214
Blair
S. S.
(
1995
)
Compartments and appendage development in Drosophila.
BioEssays
17
,
299
309
Brand
A.
,
Perrimon
N.
(
1993
)
Targeted gene expression as a means ofaltering cell fates and generating dominant phenotypes.
Development
118
,
401
415
Brook
W. J.
,
Cohen
S. M.
(
1996
)
Antagonistic interactions between wingless and decapentaplegic responsible for dorsal-ventral pattern in the Drosophila leg.
Science
273
,
1373
1377
Brook
W. J.
,
Diaz-Benjumea
F. J.
,
Cohen
S. M.
(
1996
)
Organizing spatial pattern in limb development.
Annu. Rev. Cell Dev. Biol
12
,
161
180
Busturia
A.
,
Morata
G.
(
1988
)
Ectopic expression of homeotic genes caused by the elimination of the Polycomb gene in Drosophila imaginal epidermis.
Development
104
,
713
720
Coleman
J. E.
(
1992
)
Zinc proteins: enzymes, storage proteins, transcription factors, and replication proteins.
Annu. Rev. Biochem
61
,
897
946
Crozatier
M.
,
Valle
D.
,
Dubois
L.
,
Ibnsouda
S.
,
Vincent
A.
(
1999
)
Head versus trunk patterning in the Drosophila embryo; collier requirement for formation of the intercalary segment.
Development
126
,
4385
4394
Decamillis
M.
,
Cheng
N. S.
,
Pierre
D.
,
Brock
H. W.
(
1992
)
The polyhomeotic gene of Drosophila encodes a chromatin protein that shares polytene chromosome-binding sites with Polycomb.
Genes Dev
6
,
223
232
Diaz-Benjumea
F. J.
,
Cohen
B.
,
Cohen
S. M.
(
1994
)
Cell interaction between compartments establishes the proximal-distal axis of Drosophila legs.
Nature
372
,
175
179
Dominguez
M.
,
Brunner
M.
,
Hafen
E.
,
Basler
K.
(
1996
)
Sending and receiving the hedgehog signal: control by the Drosophila Gli protein Cubitus interruptus.
Science
272
,
1621
1625
Eaton
S.
,
Kornberg
T. B.
(
1990
)
Repression of ci-D in posterior compartments of Drosophila by engrailed.
Genes Dev
4
,
1068
1077
Eberlein
S.
,
Russell
M. A.
(
1983
)
Effects of deficiencies in the engrailed region of Drosophila melanogaster.
Dev. Biol
100
,
227
237
Guillen
I.
,
Mullor
J. L.
,
Capdevila
J.
,
Sanchez-Herrero
E.
,
Morata
G.
,
Guerrero
I.
(
1995
)
The function of engrailed and the specification of Drosophila wing pattern.
Development
121
,
3447
3456
Hepker
J.
,
Wang
Q. T.
,
Motzny
C. K.
,
Holmgren
R.
,
Orenic
T. V.
(
1997
)
Drosophila cubitus interruptus forms a negative feedback loop with patched and regulates expression of Hedgehog target genes.
Development
124
,
549
558
Jiang
J.
,
Struhl
G.
(
1995
)
Protein kinase A and hedgehog signaling in Drosophila limb development.
Cell
80
,
563
572
Jiang
J.
,
Struhl
G.
(
1998
)
Regulation of the Hedgehog and Wingless signalling pathways by the F-box/WD40-repeat protein Slimb.
Nature
391
,
493
496
Kornberg
T.
(
1981
)
engrailed: a gene controlling compartment and segment formation in Drosophila.
Proc. Nat. Acad. Sci. USA
78
,
1095
1099
Lawrence
P. A.
,
Struhl
G.
(
1996
)
Morphogens, compartments, and pattern: lessons from drosophila?.
Cell
85
,
951
961
Lee
J. J.
,
von Kessler
D. P.
,
Parks
S.
,
Beachy
P. A.
(
1992
)
Secretion and localized transcription suggest a role in positional signaling for products of the segmentation gene hedgehog.
Cell
71
,
33
50
Lepage
T.
,
Cohen
S. M.
,
Diaz-Benjumea
F. J.
,
Parkhurst
S. M.
(
1995
)
Signal transduction by cAMP-dependent protein kinase A in Drosophila limb patterning.
Nature
373
,
711
715
Li
W.
,
Ohlmeyer
J. T.
,
Lane
M. E.
,
Kalderon
D.
(
1995
)
Function of protein kinase A in hedgehog signal transduction and Drosophila imaginal disc development.
Cell
80
,
553
562
Locke
J.
,
Tartof
K. D.
(
1994
)
Molecular analysis of cubitus interruptus (ci) mutations suggests an explanation for the unusual ci position effects.
Mol. Gen. Genet
243
,
234
243
Maschat
F.
,
Serrano
N.
,
Randsholt
N. B.
,
Geraud
G.
(
1998
)
engrailed and polyhomeotic interactions are required to maintain the A/P boundary of the Drosophila developing wing.
Development
125
,
2771
2780
Methot
N.
,
Basler
K.
(
1999
)
Hedgehog controls limb development by regulating the activities of distinct transcriptional activator and repressor forms of Cubitus interruptus.
Cell
96
,
819
831
Mlodzik
M.
,
Hiromi
Y.
,
Weber
U.
,
Goodman
C. S.
,
Rubin
G. M.
(
1990
)
The Drosophila seven-up gene, a member of the steroid receptor gene superfamily, controls photoreceptor cell fates.
Cell
60
,
211
224
Mohler
J.
,
Seecoomar
M.
,
Agarwal
S.
,
Bier
E.
,
Hsai
J.
(
2000
)
Activation of knot (kn) specifies the 3–4 intervein region in the Drosophila wing.
Development
127
,
55
63
Motzny
C. K.
,
Holmgren
R.
(
1995
)
The Drosophila cubitus interruptus protein and its role in the wingless and hedgehog signal transduction pathways.
Mech. Dev
52
,
137
150
Ng
M.
,
Diaz-Benjumea
F. J.
,
Cohen
S. M.
(
1995
)
Nubbin encodes aPOU-domain protein required for proximal-distal patterning in the Drosophila wing.
Development
121
,
589
599
Ohlmeyer
J. T.
,
Kalderon
D.
(
1998
)
Hedgehog stimulates maturation of Cubitus interruptus into a labile transcriptional activator.
Nature
396
,
749
753
Orenic
T. V.
,
Slusarski
D. C.
,
Kroll
K. L.
,
Holmgren
R. A.
(
1990
)
Cloning and characterization of the segment polarity gene cubitus interruptus Dominant of Drosophila.
Genes Dev
4
,
1053
1067
Pan
D.
,
Rubin
G. M.
(
1995
)
cAMP-dependent protein kinase and hedgehog act antagonistically in regulating decapentaplegic transcription in Drosophila imaginal discs.
Cell
80
,
543
552
Patel
N. H.
,
Martin-Blanco
E.
,
Coleman
K. G.
,
Poole
S. J.
,
Ellis
M. C.
,
Kornberg
T. B.
,
Goodman
C. S.
(
1989
)
Expression of engrailed proteins in arthropods, annelids, and chordates.
Cell
58
,
955
968
Phillips
R. G.
,
Roberts
I. J.
,
Ingham
P. W.
,
Whittle
J. R.
(
1990
)
The Drosophila segment polarity gene patched is involved in a position-signalling mechanism in imaginal discs.
Development
110
,
105
114
Sanicola
M.
,
Sekelsky
J.
,
Elson
S.
,
Gelbart
W. M.
(
1995
)
Drawing a stripe in Drosophila imaginal disks: negative regulation of decapentaplegic and patched expression by engrailed.
Genetics
139
,
745
756
Schwartz
C.
,
Locke
J.
,
Nishida
C.
,
Kornberg
T. B.
(
1995
)
Analysis of cubitus interruptus regulation in Drosophila embryos and imaginal disks.
Development
121
,
1625
1635
Simmonds
A. J.
,
Brook
W. J.
,
Cohen
S. M.
,
Bell
J. B.
(
1995
)
Distinguishable functions for engrailed and invected in anterior-posterior patterning in the Drosophila wing.
Nature
376
,
424
427
Simpson
P.
,
Grau
Y.
(
1987
)
The segment polarity gene costal-2 inDrosophila. II. The origin of imaginal pattern duplications.
Dev. Biol
122
,
201
209
Slusarski
D. C.
,
Motzny
C. K.
,
Holmgren
R.
(
1995
)
Mutations that alter the timing and pattern of cubitus interruptus gene expression in Drosophila melanogaster.
Genetics
139
,
229
240
Speicher
S. A.
,
Thomas
U.
,
Hinz
U.
,
Knust
E.
(
1994
)
The Serrate locus of Drosophila and its role in morphogenesis of the wing imaginal discs: control of cell proliferation.
Development
120
,
535
544
Tabata
T.
,
Kornberg
T. B.
(
1994
)
Hedgehog is a signaling protein with a key role in patterning Drosophila imaginal discs.
Cell
76
,
89
102
Tabata
T.
,
Schwartz
C.
,
Gustavson
E.
,
Ali
Z.
,
Kornberg
T. B.
(
1995
)
Creating a Drosophila wing de novo, the role of engrailed, and the compartment border hypothesis.
Development
121
,
3359
3369
Theodosiou
N. A.
,
Zhang
S.
,
Wang
W. Y.
,
Xu
T.
(
1998
)
slimb coordinates wg and dpp expression in the dorsal-ventral and anterior-posterior axes during limb development.
Development
125
,
3411
3416
Thummel
C.
,
Pirrotta
V.
(
1991
)
Technical notes: new CaSpeR P-element vectors.
Drosophila Information Service
71
,
150
–.
Vervoort
M.
,
Crozatier
M.
,
Valle
D.
,
Vincent
A.
(
1999
)
The COE transcription factor Collier is a mediator of short-range Hedgehog-induced patterning of the Drosophila wing.
Curr. Biol
9
,
632
639
Wessells
R. J.
,
Grumbling
G.
,
Donaldson
T.
,
Wang
S. H.
,
Simcox
A.
(
1999
)
Tissue-specific regulation of vein/EGF receptor signaling in Drosophila.
Dev. Biol
216
,
243
259
Zecca
M.
,
Basler
K.
,
Struhl
G.
(
1995
)
Sequential organizing activities of engrailed, hedgehog and decapentaplegic in the Drosophila wing.
Development
121
,
2265
2278
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