Duong_H_2008b

Transformation of eye to antenna by misexpression of a single
gene
Hao A. Duonga,1
, Cheng Wei Wangb,c,1
, Y. Henry Sunb,c,*, Albert J. Coureya,*
a
Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive, East, Los Angeles,
CA 90095-1569, USA
b
Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan, ROC
c
Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei, Taiwan, ROC
A R T I C L E I N F O
Article history:
Received 28 June 2007
Received in revised form
26 September 2007
Accepted 27 September 2007
Available online 4 October 2007
Keywords:
Dip3
Transformation
Duplication
Cell cycle
Pattern formation
Eye development
Antennal development
Cell fate determination
A B S T R A C T
In Drosophila, the eye and antenna originate from a single epithelium termed the eye-
antennal imaginal disc. Illumination of the mechanisms that subdivide this epithelium
into eye and antenna would enhance our understanding of the mechanisms that restrict
stem cell fate. We show here that Dip3, a transcription factor required for eye development,
alters fate determination when misexpressed in the early eye-antennal disc, and have
taken advantage of this observation to gain new insight into the mechanisms controlling
the eye-antennal switch. Dip3 misexpression yields extra antennae by two distinct mech-
anisms: the splitting of the antennal field into multiple antennal domains (antennal dupli-
cation), and the transformation of the eye disc to an antennal fate. Antennal duplication
requires Dip3-induced under proliferation of the eye disc and concurrent over proliferation
of the antennal disc. While previous studies have shown that overgrowth of the antennal
disc can lead to antennal duplication, our results show that overgrowth is not sufficient
for antennal duplication, which may require additional signals perhaps from the eye disc.
Eye-to-antennal transformation appears to result from the combination of antennal selec-
tor gene activation, eye determination gene repression, and cell cycle perturbation in the
eye disc. Both antennal duplication and eye-to-antennal transformation are suppressed
by the expression of genes that drive the cell cycle providing support for tight coupling
of cell fate determination and cell cycle control. The finding that this transformation occurs
only in the eye disc, and not in other imaginal discs, suggests a close developmental and
therefore evolutionary relationship between eyes and antennae.
Ó 2007 Elsevier Ireland Ltd. All rights reserved.
1. Introduction
In Drosophila melanogaster, the eye and antenna originate
from a cluster of 23 cells set aside during embryonic devel-
opment. During the three larval instars, this cell cluster pro-
liferates continuously and organizes into an epithelial sac
termed the eye-antennal imaginal disc. During late larval
and pupal development, the anterior lobe of this epithelium
(the antennal disc) gives rise to the antenna, while the pos-
terior lobe (the eye disc) gives rise to the eye. The eye or
antennal identity of these domains is not determined until
mid or late second larval instar with the restricted expres-
sion of genes such as eyeless (ey) in the eye disc and cut (ct)
in the antennal disc (Garcia-Bellido and Merriam, 1969;
0925-4773/$ - see front matter Ó 2007 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.mod.2007.09.012
* Corresponding authors. Tel.: +886 2 2788 3605; fax: +886 2 2782 6085 (Y.H. Sun); Tel.: +1 310 825 2530; fax: +1 310 206 4038 (A.J. Courey).
E-mail addresses: mbyhsun@gate.sinica.edu.tw (Y.H. Sun), courey@chem.ucla.edu (A.J. Courey).
1
These authors contributed equally to this paper.
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Kenyon et al., 2003; Kumar and Moses, 2001; Postlethwait
and Schneiderman, 1971).
During the mid to late second larval instar, the compo-
nents of the retinal determination gene network (RDGN),
including eyeless (ey), twin of eyeless (toy), eyes absent (eya), sine
oculis (so), and dachshund (dac), are first co-expressed in the eye
field (Kenyon et al., 2003; Kumar and Moses, 2001). Each RDGN
gene encodes a conserved transcription factor that is required
for normal retinal development (Bonini et al., 1993; Cheyette
et al., 1994; Mardon et al., 1994; Quiring et al., 1994). Over-
expression of these genes individually or in combination in
other imaginal discs including the antennal, leg, wing, geni-
tal, and haltere discs can induce ectopic eye development,
but only in the presence of the products of all the other RDGN
genes. The mechanisms that control RDGN expression are
complex. While toy appears to act first, a myriad of cross-reg-
ulatory and feedback interactions allow these factors to en-
hance each other’s ability to induce ectopic eyes (Bonini
et al., 1997; Chen et al., 1997; Halder et al., 1995; Pappu and
Mardon, 2002; Pignoni et al., 1997; Shen and Mardon, 1997).
Antennal determination is thought to require homothorax
(hth), extradenticle (exd), and Distal-less (Dll). Loss-of-function
mutations in any one of these genes leads to antenna-to-leg
transformation (Casares and Mann, 1998; Cohen et al., 1989;
Pai et al., 1998; Sunkel and Whittle, 1987), while ectopic
expression of either hth or Dll produces ectopic antennae in
the head, leg, wing, or genitals, but only in the presence of
the product of the other gene (Casares and Mann, 1998; Dong
et al., 2000; Gorfinkiel et al., 1997). Analysis of the interactions
among these genes and their products reveals that Hth is re-
quired for nuclear localization of Exd, and only in the pres-
ence of Hth can nuclear Exd produce ectopic antennae. Dll
and Hth, on the other hand, function cooperatively and in
parallel to regulate normal antennal development.
Transdetermination, a process whereby already deter-
mined imaginal disc cells change fate to that of another disc,
has been observed in many Drosophila imaginal discs, giving
rise, for example, to eye-to-wing, wing-to-leg, leg-to-antenna,
and antenna-to-wing transformations (Maves and Schubiger,
2003). A hallmark of transdetermination is the ‘‘transdeter-
mination weak point’’, a small cell cluster in each imaginal
disc that has a high probability of changing fate in response
to fragmentation of the disc through the weakpoint or misex-
pression of the Wnt-family signaling protein Wingless (Wg) in
the weakpoint. Cell proliferation has an essential role in this
process and cells about to undergo transdetermination exhi-
bit a distinct cell cycle profile that is not seen in normal devel-
opment (Sustar and Schubiger, 2005).
Since the eye and antenna originate from the same cell
population and are specified relatively late in development,
it is perhaps not surprising that an antenna can be regener-
ated from in vivo culture of an eye disc (Gehring and Schubi-
ger, 1975; Schubiger and Alpert, 1975). However, neither
mechanical disc fragmentation followed by regeneration nor
over-expression of wg, the two treatments that induce other
forms of transdetermination, induce eye-to-antenna transde-
termination (Maves and Schubiger, 2003). Furthermore, the
conversion of the eye disc to an antennal fate by misexpres-
sion of antennal determination genes such as exd, Dll, or hth
has not been previously demonstrated.
In this study we show that misexpression of Dip3, which
encodes a MADF/BESS domain family transcription factor re-
quired for cell type specification during late eye development
(Bhaskar and Courey, 2002; unpublished data), perturbs the
eye-antennal decision. By pursuing this observation, we have
gained new insight into the mechanisms that control this
switch. Expression of Dip3 in the early eye-antennal disc leads
to both eye-to-antenna transformation, in which the eye disc
gives rise to one or more partial or complete antennae, as well
as antennal duplication, in which the antennal disc gives rise
to two or more antennae. Both of the phenotypes may result
in part from perturbation of the cell cycle, since expression of
cell cycle genes prevents their appearance. Antennal duplica-
tion occurs when cell cycle perturbation leads to under-prolif-
eration of the eye disc and concurrent over-proliferation and
splitting of the antennal disc, while eye-to-antenna transfor-
mation results from cell cycle perturbation along with down-
regulation of retinal determination genes and concurrent up-
regulation of antennal determination genes in the eye disc.
These findings provide support for the idea that cell fate
determination is intimately coupled to the cell cycle. Further-
more, the ability of Dip3 to reprogram the eye disc, but not
other discs, to an antennal fate implies a close relationship
between these two sense organs.
2. Results
2.1. Dip3 misexpression results in antennal duplication
and eye-to-antenna transformation
In a screen for genes that perturb eye development when mis-
expressed, we randomly integrated a UAS/promoter-contain-
ing P-element (Brand and Perrimon, 1993; Rorth, 1996) into
the genome. An insertion immediately upstream of the Dip3
coding region was found to result in the appearance of extra
antennae when combined with the ey-Gal4 driver (Fig. 1). Sev-
eral lines of evidence (see below) lead us to conclude that
these extra antennae are of two distinct origins: some result
from antennal duplication, while others result from eye-to-
antenna transformation. In antennal duplication (Fig. 1B),
the extra antennae arise from over-proliferation and splitting
of the antennal disc into multiple domains, each of which
gives rise to an antenna. In this case the extra antennae are
located anterior to the antennal foramen (dashed line), where
antennae are normally found. In eye-to-antenna transforma-
tion, the extra antennae arise from the transformed eye disc
and are therefore located posterior to the antennal foramen
(Fig. 1C), where eyes are normally found.
In previous cases where extra antennae were initially
thought to arise from eye-to-antenna transformation, subse-
quent analysis showed that they were more likely to be the re-
sult of antennal duplication (Kenyon et al., 2003). Evidence that
the extra antennae observed in eyDip3 flies do, in some cases,
result from the transformation of eye tissue to an antennal fate
comesfromourobservation of partial eye-to-antenna transfor-
mations. In mild to moderate partial transformations, the eye
consists exclusively of ommatidial units, but bulges out or
forms a rod-shaped structure (Fig. 1D and E), suggesting that
although eye tissue identity is intact, the eye is assuming a
M E C H A N I S M S O F D E V E L O P M E N T 1 2 5 ( 2 0 0 8 ) 1 3 0 –1 4 1 131

shape similar to that of an antenna. In strong partial transfor-
mations, the eye domain contains the proximal portion of an
antenna tipped with ommatidia (Fig. 1F). Finally, in complete
transformations, ommatidia are absent and are replaced with
a complete antenna posterior to the antennal foramen (Fig. 1C).
The phenotypes described above are only observed when
flies are raised at 18 °C, resulting in low levels of Dip3 expres-
sion. At higher temperatures (25–29 °C) we observe complete
lethality due to deletion of most or all of the head. As will
be discussed below, this is likely due to inhibition of cell pro-
liferation by misexpressed Dip3.
To confirm that the extra antennae are due to Dip3 mis-
expression, we utilized a completely independent insertion
of the EP element generated by the Drosophila genome pro-
ject that maps 21 base pairs upstream of the Dip3 transcrip-
tional start site. This insert was also found to generate
extra antennae when combined with the ey-Gal4 driver
(data not shown). In addition, we created germ-line trans-
formants of a UAS-Dip3 construct and found that driving
expression of this construct with the ey-Gal4 driver also
resulted in extra antennae. This phenotype apparently
requires both the MADF and BESS domains of Dip3 since
Fig. 1 – Dip3 misexpression produces antennal duplication as well as eye-to-antenna transformation phenotypes. Scanning
electron micrographs of a wildtype fly head (A) or of heads from flies in which Dip3 was misexpressed using the ey-Gal4
driver (B–F). (B) An antenna duplication fly head. This fly exhibits two reduced eyes (e), and three antennae (a), all located
anterior to the antennal foreman (dashed line). (C) A complete eye-to-antenna transformation fly head. This fly has one eye
(e), two normal antennae (a), and one extra antenna (arrow) located posterior to the antennal foreman where the missing eye
should be. (D–F) Partial eye-to-antenna transformation fly heads of increasing severity. In mild or moderate partial
transformations, the eye consists exclusively of ommatidia but bulges out (arrow in D) or forms a rode shape structure (arrow
in E). In a nearly complete transformation, the eye is replaced with a structure consisting of the proximal portion of an
antenna, tipped with ommatidia (arrow in F).
132 M E C H A N I S M S O F D E V E L O P M E N T 1 2 5 ( 2 0 0 8 ) 1 3 0 –1 4 1

deletion constructs lacking either domain did not yield ex-
tra antennae (data not shown).
The use of other Gal4 drivers (e.g., dpp-Gal4, C765-Gal4,
GMR-Gal4) to direct Dip3 expression in other tissues or at
other times during eye development does not result in ectopic
antennae (data not shown). Thus Dip3 appears to have a spe-
cific ability to produce extra antennae in the eye-antennal
disc. This ability is highly sensitive to Dip3 expression level
and restricted to a narrow developmental time window. At-
tempts to separate the two phenotypes using the temporal
and regional gene expression targeting system (TARGET)
(McGuire et al., 2003) were not fruitful due to the narrow
developmental time window separating the two phenotypes.
2.2. Molecular evidence for antennal duplication
An examination of the dac expression pattern in the eyDip3
eye-antennal discs reveals two different patterns, one most
likely corresponding to antennal duplication and the other
to eye-to-antenna transformation. In wild-type third instar
larvae, dac is expressed in a broad stripe around the morpho-
genetic furrow in the eye disc, and in a single circular domain
in the antennal disc that constitutes the future A3 antennal
segment (Dong et al., 2002) (Fig. 2A and A0
). However, a large
proportion of Dip3 misexpressing discs display multiple circu-
lar dac expression domains and no stripe. Some of these discs
consist of a single large sac of epithelium, and show expres-
sion of Dll, the product of which normally marks the antennal
primordium (Cohen et al., 1989; Dong et al., 2000; Gorfinkiel
et al., 1997), in domains overlapping the extra circular dac
Fig. 2 – Antennal duplication results from over-proliferation
and duplication of the antennal disc at the expense of the
eye disc. Third instar larval eye-antennal imaginal discs
were stained with the indicated antibodies. (A,A0
,B,B0
) Wild-
type discs. At this stage, the eye-antennal disc consists of
two distinct epithelial lobes, the anterior antennal disc and
the posterior eye disc. (A,A0
) Double staining with
antibodies against Dac and Dll shows that dac is expressed
in a circular domain in the antennal disc and in a stripe
along the morphogenetic furrow in the eye disc, while Dll is
only expressed in the antennal disc. (B,B0
) Double staining
with Dac and Elav antibodies shows that Elav is expressed
only posterior to the morphogenetic furrow of the eye disc.
(E,E0
,F,F0
) Discs from larvae in which Dip3 was misexpressed
using the ey-Gal4 driver. (E,E0
) Double staining of an
antennal duplication disc with Dac and Dll antibodies
shows that dac and Dll are expressed in two circular
domains contained within a single epithelial lobe. (F,F0
)
Double staining of an antennal duplication disc with Dac
and Elav antibodies shows the presence of a reduced eye
domain. This disc contains a small posterior lobe (arrow), in
addition to a large anterior duplicated antennal disc.
Expression of Elav in the small lobe indicates that it is a
reduced eye domain. (G) Disc from a larva in which Notch
was over-expressed using the antennal disc-specific OK384-
Gal4 driver. This yields two to threefold overgrowth of the
antennal disc (compare to wild-type disc (C) shown at the
same magnification), but no apparent antennal duplication
as revealed by staining with Dll antibody. (D,H) Triple
staining for Wg, Dll and dpp-lacZ showed the formation of
an extra proximal-distal axis, where ectopic wg and dpp
expression domains intersect, in antennal duplication discs
(compare Fig. 2H to 2D).
c

expression domains (Fig. 2E and E0
). Similar discs have previ-
ously been observed in response to inhibition of Notch signal-
ing, interference with cell cycle exit, activation of GTPases
(Rac1/Cdc42), or activation of EGFR (Go, 2005; Kenyon et al.,
2003; Kumar and Moses, 2001; Pimentel and Venkatesh,
2005). In agreement with the conclusion from a previous anal-
ysis (Kenyon et al., 2003), we suggest that these discs repre-
sent antennal duplication. In other words, the multiple
circular dac/Dll expression domains in these discs all derive
from the antennal region of the eye-antennal imaginal disc.
In support of the idea that supernumerary circular dac/Dll
expression domains in these discs result from splitting of the
antennal domain and not from transformation of the eye
disc, these discs often contain a small posterior lobe (Fig. 2F,
arrow) in addition to the large anterior lobe. When such discs
are stained with antibodies to Elav (Fig. 2F0
), which marks dif-
ferentiated photoreceptors, we observe Elav in the small pos-
terior lobe. Thus, the posterior lobe represents a reduced eye
disc, while the anterior region containing the multiple circu-
lar dac/Dll expression domains represents an enlarged and
split antennal field. This conclusion is consistent with the
observation that the antennal duplication heads often con-
tain reduced eyes (Fig. 1B). Thus, antennal duplication ap-
pears to result, at least in part, from reduction of the eye
field, leading to compensatory over-proliferation and splitting
of the antennal field.
To determine if overgrowth of the antennal disc is sufficient
for antennal duplication, we took advantage of the ability of
activatedNotch (Nact
) to stimulate cell proliferation.While mis-
expression of Nact
in the antennal disc (using the antennal disc-
specific OK384-Gal4 driver) induced 2- to 3-fold overgrowth of
the antennal disc, we observed neither duplication of the Dll
expression domain in larval discs nor extra adult antennae
(compare Fig. 2G to 2C). This suggests that generation of dupli-
cated antennae requires not only overgrowth of the antennal
disc, but also the reduction of the eye disc. Thus, active com-
munication between the eye and antennal discs may contrib-
ute to fate determination in the antennal disc.
The formation of the duplicated antenna suggests the
existence of an extra proximal-distal (PD) axis in the dupli-
cated antennal disc. Previous studies have shown that the for-
mation of the PD axis requires the intersection of domains
with high levels of wg and dpp expression (Brook and Cohen,
1996; Campbell et al., 1993; Diaz-Benjumea et al., 1994; Jiang
and Struhl, 1996; Lecuit and Cohen, 1997; Penton and Hoff-
mann, 1996). Accordingly, the antennal duplication discs ex-
hibit ectopic wg and dpp expression domains that intersect
at the center of the duplicated Dll expression domain (com-
pare Fig. 2H to 2D).
2.3. Molecular evidence for eye-to-antenna transformation
In contrast to the antennal duplication discs described above,
in which the extra circular dac expression domains are lo-
cated within the anterior antennal disc, some of the eyDip3
eye-antennal discs contain multiple circular dac expression
domains distributed between the anterior antennal field and
the posterior eye field. In these discs, Dll is co-expressed with
dac only in the antennal field and not in the eye field (Fig. 3A).
We suggest that these discs represent eye-to-antenna trans-
formations. This interpretation is supported by the following
lines of evidence. First, ct, which encodes a marker of the 2nd
instar antennal disc that can suppress ey expression and
transform an eye to a partial antenna (see the subsequent
section for details), is ectopically expressed in the eye field
in these discs (compare Fig. 3C and 3D). This observation sug-
gested that the eye disc has been re-programmed to an anten-
Fig. 3 – Eye-to-antenna transformation discs. Eye-antennal
imaginal discs were stained with antibodies against the
indicated markers. (A,B,D,F) Discs from larvae in which Dip3
was misexpressed using the ey-Gal4 driver. (C,E) Wild-type
discs. (A) An eye-to-antennal transformation third instar
disc double stained with Dac and Dll antibodies. The
anterior antennal disc contains a normal single circular dac/
Dll expressing domain, while the transformed posterior eye
disc has split into two antennal domains as revealed by the
two circular dac expression domains. Dll is not expressed in
the transformed eye disc (compare to Fig. 2A and 2A0
). (B) A
third instar larval eye-antennal disc stained with antibodies
against Dac and Elav. In this partial eye-to-antenna
transformation disc, the Elav expression domain in the eye
disc is surrounded by a dac expression domain, implying
that the outer region of the eye disc has assumed an
antennal identity (compare to Fig. 2B and 2B0
). (C,D) Discs
from second instar larval eye-antennal discs stained with
anti-Ct antibody. In the wildtype disc (C), Ct is only
expressed in the antennal field , while in an eyDip3 disc (D),
Ct is ectopically expressed in the eye field suggesting an
eye-to-antenna transformation. (E,F) Third instar larval eye-
antennal discs stained with Dll and Hth antibodies. In the
eyDip3 disc (F), the hth expression pattern in the eye
domain is transformed to an antenna-like pattern, while the
Dll expression pattern is unchanged relative to the wild-
type disc (E).

nal identity. Furthermore, while Dll is not expressed in the eye
field in these discs, the expression pattern of the antennal
determination gene hth (Casares and Mann, 1998; Pai et al.,
1998) in the eye field is altered to resemble its expression pat-
tern in the antennal field (compare Fig. 3E and 3F). Lastly, in
discs likely to represent partial eye-to-antenna transforma-
tions, elav is expressed in the eye field. However, the expres-
sion domain is localized to the center rather than the
posterior part of the field and is surrounded by a circular do-
main of dac expression (Fig. 3B). This expression pattern im-
plies that the outer part of the eye field has been
transformed to an antennal identity while the center of the
field still retains eye tissue identity.
While previous studies have demonstrated a critical role for
Dll in the normal antennal development program (Casares and
Mann, 1998; Cohen et al., 1989; Dong et al., 2000), the absence of
Dll expression in eye discs transformed by Dip3 to an antennal
fate (Fig. 3B0
and3F) suggests the existence of a Dll-independent
mechanism of antennal development in the eye disc. Support
for this interpretation is provided by the observation that re-
moval of one copy of Dll does not alter the eyDip3 phenotype,
whereas removal of one copy of hth almost completely sup-
presses the extra antenna phenotype (data not shown).
Thus, antennal duplication and eye-to-antenna transfor-
mation discs display distinct molecular signatures suggesting
that these phenotypes are governed by distinct mechanisms.
2.4. Non-cell-autonomous inhibition of retinal
determination genes and activation of antennal selector
genes by Dip3
Transformation of eyes to antennae by Dip3 is likely to require
repression of members of the RDGN such as ey and dac as well
as activation of antenna-specific genes such as ct and hth. To
explore this possibility, we examined third instar eye discs
containing clones of Dip3-over-expressing cells. In the wild-
type fly, ey is expressed in the second and third instar eye disc
prior to being shut off starting from the posterior of the disc
following passage of the morphogenetic furrow. As men-
tioned previously, dac is expressed in a broad stripe straddling
the morphogenetic furrow.
Misexpression of Dip3 in clones was found to result in
down-regulation of ey and dac expression. Surprisingly, this
Fig. 4 – Dip3 inhibits expression of the retinal determination
gene network and activates antennal selector genes.
(A,A0
,A00
) A third instar larval eye disc containing two Dip3
misexpressing clones marked with GFP. The disc was
double stained with antibodies against Ey and Dac. ey and
dac expression are inhibited in and around the clone
positioned along the dorsoventral (D–V) midline (arrow), but
not in the clone located outside of that region (arrowhead).
MF: morphogenetic furrow. (B,C) Bright field images of adult
eyes showing the inhibition of photoreceptor development
along the D–V midline (compare B to C, arrow) when Dip3 is
misexpressed in that region with the eyg-Gal4 driver. This
inhibition is strongest at the anterior edge of the eye. (D–I)
Third instar larval eye discs in which GFP expression or the
expression of both GFP and Dip3 were driven using the eyg-
Gal4 driver. The expression domain of GFP in each disc is
indicated by a dotted line. Discs were stained with
antibodies against Hth (D,E), Ey and Ct (F–G00
), or Wg (H,I).
Arrowheads in E, G, G0
, G00
, and I indicate ectopic activation
of hth, ct, and wg, and ectopic repression of ey.
c

effect is non-cell-autonomous as the zone of RDGN down-reg-
ulation extends beyond the borders of the Dip3-over-express-
ing clone. The ability of Dip3-over-expressing clones to
repress RDGN expression depends on the location of the
clone. In particular, only clones located near the dorsoventral
(DV) midline (Fig. 4A, A0
, A00
, arrow) lead to decreased RDGN
expression. Thus, Dip3 may co-operate with one or more DV
midline-localized factors to inhibit RDGN expression.
To examine this position-dependence further, we selec-
tively over-expressed Dip3 along the D–V midline using
the eyg-Gal4 driver. In eygDip3 flies, photoreceptor devel-
opment is inhibited along the D–V midline, with the stron-
gest inhibition at the anterior of the eye (compare Fig. 4C
to 4B). Consistent with the idea that retinal cells are being
reprogrammed to antenna, we observe non-cell-autono-
mous activation of antennal selector genes such as hth
(Fig. 4D and E) and ct (Fig. 4F, F0
, G, G0
) and repression of
retinal determination genes such as ey (Fig. 4F, F00
, G, G00
).
Therefore, Dip3 appears to elicit one or more signals that
both inhibit RDGN expression and promote antennal selec-
tor gene expression. In addition, eygDip3 also led to the
non-cell-autonomous induction of wg expression (Fig. 4H–
I). The induction of wg at a position near the dpp-express-
ing morphogenetic furrow may create an intersection of
high Wg and Dpp signaling, thereby inducing formation
of a proximodistal axis.
2.5. ct over-expression can inhibit ey expression and
transform eyes to partial antennae
While ey is expressed ubiquitously throughout the first instar
eye-antennal disc, it is shut off in the antennal primordium in
early to mid second instar larvae at approximately the same
time that ct is switched on in this region (Fig. 5A and B; Ken-
yon et al., 2003; Kumar and Moses, 2001). To determine if Ct is
sufficient for ey down regulation in the eye disc, we generated
ct over-expressing clones in the eye. Over-expression of ct
inhibited ey expression cell-autonomously, suggesting that
the reduced expression of ey in the 2nd instar antennal disc
results from up-regulation of ct (Fig. 5C–C0
).
If the ability of Dip3 to transform eyes to antennae results
from its ability to induce antennal markers such as ct and pre-
vent the expression of retinal determination genes such as ey,
then ct over-expression might be sufficient for eye-to-antenna
transformation. Indeed, ey-Gal4-driven expression of ct leads
to partial eye-to-antenna transformation resembling the par-
tial transformations observed in eyDip3 flies (Fig. 5D).
2.6. The role of eye disc proliferation in antennal
duplication and eye-to-antenna transformation
The reduced size of the eye field that often results from Dip3
misexpression suggests that Dip3 either inhibits cell prolifer-
ation or induces cell death. To distinguish these two possibil-
ities, we looked at DNA synthesis and apoptosis in eyDip3
discs by observing the levels of BrdU labeling and activated
Drice, respectively. The reduced discs show a significant
reduction in BrdU labeling (Fig. 6A), but no induction of acti-
vated Drice (data not shown). Co-expression with the anti-
apoptotic protein p35 did not rescue the eye defect (data not
shown), further confirming the absence of a role for apoptosis
in producing the eyDip3 phenotypes.
To explore the role of the cell proliferation defect in gener-
ating Dip3 misexpression phenotypes, we co-expressed Dip3
with activated Notch (Nact
), which is known to stimulate cell
proliferation (Reynolds-Kenneally and Mlodzik, 2005; Tsai
and Sun, 2004). When Dip3 was expressed alone, 17% of the
resulting flies had normal eyes and antennae, 5% had normal
antennae but small eyes, 40% had extra antennae, and 38%
were headless. In flies coexpressing Nact
and Dip3, the average
severity of the defect was significantly reduced—54% had nor-
mal eyes, 19% had normal antennae but small eyes, 25% had
extra antennae, and 2% were headless. In eye disc develop-
ment, N promotes global growth through eyg and upd (Chao
et al., 2004). Accordingly, coexpression of eyg or upd with
Dip3 also greatly reduces the severity of the Dip3 misexpres-
sion phenotype (Fig. 6C). Finally, coexpression of Dip3 with
CycE, which drives cell proliferation, also results in suppres-
sion of the Dip3 misexpression phenotype (Fig. 6B and C). In
contrast, coexpression of twin of eyeless does not leads to res-
cue, showing that rescue is not the consequence of reduced
Dip3 expression, which could theoretically result from the
presence of an extra UAS. In conclusion, these findings indi-
cate that both antennal duplication and eye-to-antennae
transformation are due, in part, to the ability of Dip3 to inter-
fere with cell proliferation in the eye disc.
3. Discussion
We have discovered that ectopic expression of a single gene in
the early eye-antennal disc can lead to both antennal duplica-
tion and eye-to-antennal transformation. Both of these pheno-
types appear to result, in part, from inhibition of cell cycle
progression since suppression of the growth defect in these
discs by coexpression of genes that drive cell-cycle progression
prevents both phenotypes. Although previous studies also sug-
gested a link between growth and developmental fate in the
eye-antennal disc, the current study adds a number of new in-
sights: (1) Previous studies showedthat inhibiting growth of the
eyedisc leads to overproliferation and duplication of the anten-
nal disc. The current study supports this idea, but also shows
that antennal disc overproliferation is not sufficient for dupli-
cation, which may also involve communication between the
eye and antennal discs. (2) This is first study to suggest a con-
nection between the cell-cycle progression and the eye-anten-
nal decision.
We have recently created loss-of-function alleles of Dip3
(Unpublished data). While these demonstrate a role for Dip3
in late eye development, they do not show a role in early fate
determination in the eye-antennal field. This may be due to
redundancy as there are 14 other homologous MADF/BESS do-
main transcription factors encoded in the Drosophila
genome.
3.1. Dip3 induces antennal duplication and eye-to-
antenna transformation
Antagonism between the N and EGFR signaling pathways
influences developmental fate in the eye-antennal disc lead-

ing to a loss of eye tissue and the appearance of extra anten-
nae (Kumar and Moses, 2001). Although this phenotype was
originally suspected to represent eye-to-antennal transfor-
mation, subsequent analysis suggests that it most likely rep-
resents antennal duplication. Specifically, the absence of the
N signal leads to a failure in eye disc proliferation resulting
in compensatory over-proliferation of the antennal disc and
its subdivision into multiple antennae (Kenyon et al., 2003).
Consistent with the idea that the extra antennae result from
under-proliferation of the eye field, it was found that the phe-
notype was largely suppressed by over-expression of CycE to
drive the cell cycle.
In this study, we also find that inhibition of eye disc growth
leads to antennal duplication. But in addition, we show that
the same treatment that leads to antennal duplication can
also direct the transformation of eyes to antennae. These
two phenotypes are anatomically distinct. This anatomical
distinction is evident in adults: antennae resulting from
Fig. 5 – ct over-expression leads to partial eye to antenna transformation. (A) Wildtype first instar larval eye-antennal disc
stained with Ey antibody showing that Ey is expressed throughout the disc. (B) Second instar larval eye-antennal discs
double stained with Ct and Ey antibodies showing that, by this stage, ct is coming on while ey is being shut off in the antennal
disc. (C,C0
) A second instar disc containing ct over-expressing clones marked with GFP. Staining of the disc with Ey antibodies
shows Ey downregulation in the ct-expressing clones suggesting that Ct can block Ey expression. (D) Lateral view of an adult
fly head in which UAS-ct was misexpressed using the ey-Gal4 driver (anterior to the left) showing the transformation of an
eye to the first and second antennal segments (arrow).
Fig. 6 – Driving cell proliferation prevents antennal duplication and eye-to-antenna transformation. (A) Eye-antennal disc
from early third instar larva in which Dip3 was misexpressed using the ey-Gal4 driver. The disc was double stained with
antibodies against BrdU to reveal cell proliferation and the antennal disc marker Ct (A). Lack of BrdU incorporation in the eye
disc indicates that the undergrowth of the eye disc is due to a failure of cell proliferation rather than increased apoptosis.
(B) Eye-antennal disc from early third instar larva in which Dip3 and CycE were expressed using the ey-Gal4 driver. The disc
was double stained with antibodies against BrdU and Dac. CycE over-expression prevents the cell proliferation defect that
normally results from Dip3 misexpression. (C) Phenotypes of flies expressing Dip3 and coexpressing CycE, eyg, upd, or Nact
.
These factors, which all drive cell proliferation in the eye disc, significantly reduce the severity of the Dip3 misexpression
defect. n is the number of flies examined.

antennal duplication are found anterior to the antennal fora-
men, while the antennae resulting from eye-to-antenna
transformation are found posterior to the antennal foramen.
It is also apparent in larval eye-antennal imaginal discs:
antennal duplication discs exhibit multiple circular dac
expression domains within a single sac of epithelium (the
antennal disc), while eye-to-antennal transformation discs
exhibit two or more circular dac expression domains spread
over both the eye and antennal discs. The two types of discs
display distinct molecular signatures as well: the antennal
duplication discs exhibit duplicated Dll expression domains,
while the eye discs undergoing transformation to antennae
lack Dll expression.
Perhaps the most persuasive evidence that Dip3 can di-
rect eye-to-antennal transformation is provided by the
observation of eyes that are only partially transformed to
antennae since is very difficult to reconcile these partial
transformations with the idea of antennal duplication. In
some cases, we observe proximal antennal segments tipped
with eye tissue. In accord with this phenotype, some third
instar larval eye discs display a central domain of Elav-posi-
tive differentiating photoreceptors surrounded by a circular
dac domain.
The arguments presented above support the idea that
antennal duplication and eye-to-antennal transformation
are mechanistically distinct phenomena, and the remainder
of the discussion assumes this to be the case. However, we
cannot exclude the possibility that these two phenotypes
are two manifestations of a single mechanism. For example,
the discs exhibiting duplicated Dll domains may represent
complete transformations, while the discs lacking duplicated
Dll domains, but containing Elav may represent partial
transformations.
3.2. Antennal disc overgrowth is required but not
sufficient for antennal duplication
Our data show that discs undergoing antennal duplication as
a result of Dip3 expression are comprised of a severely dimin-
ished eye region and an enlarged antennal region. As shown
by BrdU labeling experiments, these antennal duplication
discs most likely result from suppression by Dip3 of cell pro-
liferation in the eye field leading to overproliferation of the
antennal disc. This conclusion is supported by the ability of
factors that drive cell proliferation (e.g., Cyclin E) to alleviate
the Dip3 misexpression defect.
Many experimental manipulations that reduce the size of
the eye disc (e.g., surgical excision, induction of cell death,
or suppression of cell proliferation) lead to enlargement and
duplication of the antennal primordium (Arking, 1975; Geh-
ring and Nothiger, 1973; Martin et al., 1977; Russell, 1974;
Schubiger and Alpert, 1975). How might reduction of the eye
field lead to antennal field over-growth? One possibility is that
the eye field produces a growth inhibitory signal. Alterna-
tively, the eye field and the antennal field may compete with
each other for limited nutrients or growth factors. In support
of this latter possibility, recent studies of the role of dMyc in
wing development have demonstrated growth competition
between groups of imaginal disc cells (de la Cova et al.,
2004; Moreno and Basler, 2004).
While our results imply that antennal disc overgrowth is
required for antennal duplication, we do not believe that over-
growth is sufficient for duplication. This conclusion derives
from experiments in which we used an antennal disc specific
driver to direct over-expression of CycE or Nact
(Fig. 2F and
data not shown). This resulted in antennal overgrowth with-
out concurrent reduction in the eye disc. In this case, anten-
nal duplication was not observed. Thus, in addition to
antennal overgrowth, antennal duplication also appears to re-
quire reduction or elimination of the eye disc. Regulatory sig-
nals from the eye disc may act to prevent antennal
duplication.
3.3. Multiple requirements for eye-to-antenna
transformation
The eye and antenna discs differ in several respects: (1) Spe-
cific expression of the organ-specification genes. The eye disc
expresses the RDGN genes, while the antennal disc expresses
Dll and hth. hth is also expressed in the eye disc but in a dis-
tinct pattern from that seen in the antennal disc. In the sec-
ond instar eye disc, hth is expressed throughout the eye
disc, and collaborates with ey and teashirt (tsh) to promote cell
proliferation (Bessa et al., 2002). The hth expression domain
later retracts to only the anterior-most region of the eye disc
(Bessa et al., 2002; Casares and Mann, 1998; Pai et al., 1998).
This pattern is different from the circular expression pattern
observed in the antennal disc. (2) In the antennal disc, dpp is
expressed in a dorsal anterior wedge and wg is expressed in a
ventral anterior wedge. The intersection of Dpp and Wg sig-
naling is required to specify the proximodistal axis in the
leg and antenna (Diaz-Benjumea et al., 1994). In the early
eye disc, Wg and Dpp signaling may overlap. But as the disc
grows in size, the wg and dpp expression domain are sepa-
rated, so that there is probably no intersection between high
levels of Wg and Dpp signaling (see review by Dominguez
and Casares, 2005). (3) Whereas the partial overlap of Dll
and hth expression domains in the antennal disc is important
for proximodistal axis specification (Dong et al., 2000, 2002),
there is no Dll expression in the eye disc. Dll expression in
the center of the antennal and leg discs is induced by the
combination of high levels of Dpp and Wg signaling (Diaz-
Benjumea et al., 1994). Because there is no overlap of Dpp
and Wg signaling in the eye disc, Dll is not induced.
Therefore, efficient transformation of the eye disc into an
antennal disc requires at least three things: (1) repression of
the eye fate pathway; (2) Activation the antennal fate path-
way; and (3) the intersection of Dpp and Wg signaling, mim-
icking the situation in the antenna and leg disc that induces
proximodistal axis formation. Any one of these three condi-
tions by itself is not sufficient: (1) Loss of the RDGN genes
leads only to the loss of the eye. However, if apoptosis is
blocked, or cell proliferation is induced, in the ey2
mutant
(eyp35 or eyNact
in ey2
), then Dll can be induced in the eye
disc and extra antenna are formed (Kurata et al., 2000; Punzo
et al., 2004). The induction of Dll is not ubiquitous in the eye
disc, suggesting that the loss of ey does not autonomously
lead to the expression of Dll and the transformation to the
antennal fate. (2) Simply expressing the antennal determining
genes Dll or hth in the eye disc does not change the eye fate

into antennal fate. We found that uniform expression of Dll in
the eye disc (eyDll) resulted in mild eye reduction (data not
shown), whereas eyhth completely abolished eye develop-
ment. E132Dll caused the formation of small antenna in
the eye in about 46% of flies, whereas ptcDll and C68aDll in-
duced extra antenna but not within the eye field (Gorfinkiel
et al., 1997). Therefore, although Dll and hth are important
determinants for antennal identity, it is their specific spatial
expression patterns that determine antennal development.
(3) Creating the intersection of Wg and Dpp signaling does
not change the eye into antenna. Such manipulation in the
leg disc turned on vg and transdetermined the leg disc into
wing disc (Maves and Schubiger, 2003). Therefore, the specific
genes induced by Dpp and Wg signaling may depend on disc-
specific factors. In the eye disc, turning on Wg signaling in the
dpp expressing morphogenetic furrow only blocked furrow
progression (Treisman and Rubin, 1995).
In this study, we found that the ectopic expression of a sin-
gle gene, Dip3, can cause eye-to-antenna transformation. Dip3
apparently satisfied all three requirements. (1) Overexpres-
sion of Dip3 repressed (non-cell-autonomously) ey and dac.
The repression of ey may be due to the induction of ct. The
ability of Dip3 to simultaneously repress multiple retinal
determination genes is completely consistent with the many
known cross-regulatory interactions between these genes
(Pappu and Mardon, 2002). (2) eyDip3 turned on ct and hth.
(3) By blocking cell proliferation, eydip3 reduced the eye field
size and allowed the intersection of Dpp and Wg signaling.
Furthermore, eyDip3 induced en, which probably created an
ectopic A/P border and induced ectopic dpp/wg expression
(data not shown).
Interference with cell cycle progression appears to be a
common link between the two phenotypes described in this
study. In the case of antennal duplication, interference with
eye disc growth leads to antennal disc overgrowth, which is
a prerequisite for duplication. In the case of eye-to-antenna
transformation, eye disc undergrowth allows the required
intersection between Dpp and Wg signaling.
3.4. Possible close evolutionary relationship between eye
and antenna
The observation that Dip3 misexpression can transform the
eye field, but not other tissues, to an antennal fate suggests
a close evolutionary relationship between the eye and the an-
tenna. Previous studies have emphasized the homology be-
tween antennae and legs (Casares and Mann, 1998; Cohen
et al., 1989; Pai et al., 1998). The findings presented here that
misexpression of a single transcription factor, namely Dip3,
can transform eyes to antennae provides support for the no-
tion that the eye and antenna may also, in some sense, be
homologous to one another. Previous evidence in support of
this idea comes from the observation that similar spatial
arrangements of Wg and Dpp signaling along with a temporal
cue provided by the ecdysone signal are required for the for-
mation of the eye and the mechanosensory auditory organ
(Johnston’s organ) associated with the antenna (Niwa et al.,
2004). Small mechanosensory sensilla, such as Johnston’s or-
gan and the chordotonal organs (stretch receptors) are
thought to represent the earliest evolving sense organs. Per-
haps the eye resulted from a duplication and specialization
of such a sensillum.
4. Experimental procedures
4.1. Misexpression screening
704 EP lines (Rorth, 1996) (generated and generously provided by
Dr. Cheng-ting Chien, Institute of Molecular Biology, Academia
Sinica, Taiwan) were crossed to the ey-Gal4 driver line (Quiring
et al., 1994). In the F1 progeny from such crosses, one line (C00-
008) with an EP insertion 198 bp upstream of the Dip3 translation
start site, displayed the antenna duplication, eye-to-antenna
transformation, and eye reduction phenotypes.
4.2. Mitotic clones
Positively labeled flip-out clones expressing Dip3 were generated
by crossing EP-Dip3 flies to hs-FLP22; Act5Cy+GAL4 UAS-GFPS65T
(Ito et al., 1997). Heat-shock induction of hs-FLP22 was at 37 °C for
30 min at 24–48 h after egg laying.
4.3. Immunohistochemistry
Antibody staining was performed as described previously (Wolff,
2000). Rabbit anti-Dll antibody (Dong et al., 2000) was provided
by G. Panganiban. Guinea pig anti-Hth antibody (Casares and
Mann, 1998) was provided by R.S. Mann. Rat anti-BrdU antibody
was provided by U. Banerjee. Rabbit anti-Ey antibody (Halder
et al., 1998) was provided by U. Walldorf. Rabbit anti-activated
Drice antibody (Yoo et al., 2002) was provided by B.A. Hay. Rat
anti-Elav, mouse anti-Eya, mouse anti-Dac and mouse anti-Cut
antibodies were provided by the Developmental Studies Hybrid-
oma Bank (DSHB).
Acknowledgments
We thank Gerold Schubiger, Raghavendra Nagaraj, and Girish
Ratnaparkhi for valuable discussion; Preeta Guptan, Sudip
Mandal and Laurent Bentolila for technical assistance; and
Justin P. Kumar, Francesca Pignoni, Richard S. Mann, Grace
Panganiban, Ulrich Walldorf, Bruce A. Hay and the Develop-
mental Studies Hybridoma Bank for reagents. We thank the
anonymous reviewers for their very helpful comments and
suggestions. Confocal images were obtained in the UCLA
CNSI Advanced Light Microscopy/Spectroscopy Shared Facil-
ity and the Confocal Facility in IMB, Academia Sinica. This
work was supported by an NIH Grant (GM44522) to A.J.C.,
and by an NSC Grant (NSC 93-2312-B-001-016) to Y.H.S.
R E F E R E N C E S
Arking, R., 1975. Temperature-sensitive cell-lethal mutants of
drosophila: isolation and characterization. Genetics, 519–537.
Bessa, J., Gebelein, B., Pichaud, F., Casares, F., Mann, R.S., 2002.
Combinatorial control of Drosophila eye development by
eyeless, homothorax, and teashirt. Genes Dev. 16, 2415–2427.
Bhaskar, V., Courey, A.J., 2002. The MADF-BESS domain factor
Dip3 potentiates synergistic activation by Dorsal and Twist.
Gene 299, 173–184.

Bonini, N.M., Bui, Q.T., Gray-Board, G.L., Warrick, J.M., 1997. The
Drosophila eyes absent gene directs ectopic eye formation in a
pathway conserved between flies and vertebrates.
Development 124, 4819–4826.
Bonini, N.M., Leiserson, W.M., Benzer, S., 1993. The eyes absent
gene: genetic control of cell survival and differentiation in the
developing Drosophila eye. Cell 72, 379–395.
Brand, A.H., Perrimon, N., 1993. Targeted gene expression as a
means of altering 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.
Campbell, G., Weaver, T., Tomlinson, A., 1993. Axis specification in
the developing Drosophila appendage: the role of wingless,
decapentaplegic, and the homeobox gene aristaless. Cell 74,
1113–1123.
Casares, F., Mann, R.S., 1998. Control of antennal versus leg
development in Drosophila. Nature 392, 723–726.
Chao, J.L., Tsai, Y.C., Chiu, S.J., Sun, Y.H., 2004. Localized Notch
signal acts through eyg and upd to promote global growth in
Drosophila eye. Development 131, 3839–3847.
Chen, R., Amoui, M., Zhang, Z., Mardon, G., 1997. Dachshund and
eyes absent proteins form a complex and function
synergistically to induce ectopic eye development in
Drosophila. Cell 91, 893–903.
Cheyette, B.N., Green, P.J., Martin, K., Garren, H., Hartenstein, V.,
Zipursky, S.L., 1994. The Drosophila sine oculis locus encodes
a homeodomain-containing protein required for the
development of the entire visual system. Neuron 12, 977–996.
Cohen, S.M., Bronner, G., Kuttner, F., Jurgens, G., Jackle, H., 1989.
Distal-less encodes a homoeodomain protein required for
limb development in Drosophila. Nature 338, 432–434.
de la Cova, C., Abril, M., Bellosta, P., Gallant, P., Johnston, L.A.,
2004. Drosophila myc regulates organ size by inducing cell
competition. Cell 117, 107–116.
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., Casares, F., 2005. Organ specification-growth
control connection: new in-sights from the Drosophila eye-
antennal disc. Dev. Dyn. 232, 673–684.
Dong, P.D., Chu, J., Panganiban, G., 2000. Coexpression of the
homeobox genes Distal-less and homothorax determines
Drosophila antennal identity. Development 127, 209–216.
Dong, P.D., Dicks, J.S., Panganiban, G., 2002. Distal-less and
homothorax regulate multiple targets to pattern the
Drosophila antenna. Development 129, 1967–1974.
Garcia-Bellido, A., Merriam, J.R., 1969. Cell lineage of the
imaginal discs in Drosophila gynandromorphs. J. Exp. Zool.
170, 61–75.
Gehring, W.J., Nothiger, R., 1973. The imaginal discs of Drosophila.
In: Counce, S., Waddingtion, C. (Eds.), Developmental Systems:
Insects. Academic Press, London, pp. 211–290.
Gehring, W.J., Schubiger, G., 1975. Expression of homeotic
mutations in duplicated and regenerated antennae of
Drosophila melanogaster. J Embryol. Exp. Morphol. 33,
459–469.
Go, M.J., 2005. Activation of Rac1 or Cdc42 during early
morphogenesis of eye discs induces ectopic antennae in
Drosophila. Dev. Growth Differ. 47, 225–231.
Gorfinkiel, N., Morata, G., Guerrero, I., 1997. The homeobox gene
Distal-less induces ventral appendage development in
Drosophila. Genes Dev. 11, 2259–2271.
Halder, G., Callaerts, P., Flister, S., Walldorf, U., Kloter, U., Gehring,
W.J., 1998. Eyeless initiates the expression of both sine oculis
and eyes absent during Drosophila compound eye
development. Development 125, 2181–2191.
Halder, G., Callaerts, P., Gehring, W.J., 1995. Induction of ectopic
eyes by targeted expression of the eyeless gene in Drosophila.
Science 267, 1788–1792.
Jiang, J., Struhl, G., 1996. Complementary and mutually exclusive
activities of decapentaplegic and wingless organize axial
patterning during Drosophila leg development. Cell 86,
401–409.
Kenyon, K.L., Ranade, S.S., Curtiss, J., Mlodzik, M., Pignoni, F.,
2003. Coordinating proliferation and tissue specification to
promote regional identity in the Drosophila head. Dev. Cell 5,
403–414.
Kumar, J.P., Moses, K., 2001. EGF receptor and Notch signaling act
upstream of Eyeless/Pax6 to control eye specification. Cell 104,
687–697.
Kurata, S., Go, M.J., Artavanis-Tsakonas, S., Gehring, W.J., 2000.
Notch signaling and the determination of appendage identity.
Proc. Natl. Acad. Sci. USA 97, 2117–2122.
Lecuit, T., Cohen, S.M., 1997. Proximal-distal axis formation in the
Drosophila leg. Nature 388, 139–145.
Mardon, G., Solomon, N.M., Rubin, G.M., 1994. dachshund
encodes a nuclear protein required for normal eye and leg
development in Drosophila. Development 120, 3473–3486.
Martin, P., Martin, A., Shearn, A., 1977. Studies of l(3)c43hs1 a
polyphasic, temperature-sensitive mutant of Drosophila
melanogaster with a variety of imaginal disc defects. Dev. Biol.
55, 213–232.
Maves, L., Schubiger, G., 2003. Transdetermination in Drosophila
imaginal discs: a model for understanding pluripotency and
selector gene maintenance. Curr. Opin. Genet. Dev. 13, 472–479.
McGuire, S.E., Le, P.T., Osborn, A.J., Matsumoto, K., Davis, R.L.,
2003. Spatiotemporal rescue of memory dysfunction in
Drosophila. Science 302, 1765–1768.
Moreno, E., Basler, K., 2004. dMyc transforms cells into super-
competitors. Cell 117, 117–129.
Niwa, N., Hiromi, Y., Okabe, M., 2004. A conserved developmental
program for sensory organ formation in Drosophila
melanogaster. Nat. Genet. 36, 293–297.
Pai, C.Y., Kuo, T.S., Jaw, T.J., Kurant, E., Chen, C.T., Bessarab, D.A.,
Salzberg, A., Sun, Y.H., 1998. The Homothorax homeoprotein
activates the nuclear localization of another homeoprotein,
extradenticle, and suppresses eye development in Drosophila.
Genes Dev. 12, 435–446.
Pappu, K., Mardon, G., 2002. Retinal specification and
determination in Drosophila. In: Moses, K. (Ed.), Results and
Problems in Cell Differentiation, vol. 37. Springer, Berlin,
pp. 5–20.
Penton, A., Hoffmann, F.M., 1996. Decapentaplegic restricts the
domain of wingless during Drosophila limb patterning. Nature
382, 162–164.
Pignoni, F., Hu, B., Zavitz, K.H., Xiao, J., Garrity, P.A., Zipursky, S.L.,
1997. The eye-specification proteins So and Eya form a
complex and regulate multiple steps in Drosophila eye
development. Cell 91, 881–891.
Pimentel, A.C., Venkatesh, T.R., 2005. rap gene encodes Fizzy-
related protein and regulates cell proliferation (Fzr) and
pattern formation in the developing Drosophila eye-antennal
disc. Dev. Biol. 235, 436–446.
Postlethwait, J.H., Schneiderman, H.A., 1971. A clonal analysis of
development in Drosophila melanogaster: morphogenesis,
determination, and growth in the wild-type antenna. Dev. Biol.
24, 477–519.
Punzo, C., Plaza, S., Seimiya, M., Schnupf, P., Kurata, S., Jaeger, J.,
Gehring, W.J., 2004. Functional divergence between eyeless
and twin of eyeless in Drosophila melanogaster. Development
131, 3943–3953.
Quiring, R., Walldorf, U., Kloter, U., Gehring, W.J., 1994. Homology
of the eyeless gene of Drosophila to the Small eye gene in mice
and Aniridia in humans. Science 265, 785–789.

Reynolds-Kenneally, J., Mlodzik, M., 2005. Notch signaling
controls proliferation through cell-autonomous and non-
autonomous mechanisms in the Drosophila eye. Dev. Biol. 285,
38–48.
Rorth, P., 1996. A modular misexpression screen in Drosophila
detecting tissue-speciﬁc phenotypes. Proc. Natl. Acad. Sci.
USA 93, 12418–12422.
Russell, M.A., 1974. Pattern formation in the imaginal discs of a
temperature-sensitive cell-lethal mutant of Drosophila
melanogaster. Dev. Biol. 40, 24–39.
Schubiger, G., Alpert, G.D., 1975. Regeneration and
duplication in a temperature sensitive homeotic mutant
of Drosophila melanogaster. Dev. Biol. 42,
292–304.
Shen, W., Mardon, G., 1997. Ectopic eye development in
Drosophila induced by directed dachshund expression.
Development 124, 45–52.
Sunkel, C., Whittle, J., 1987. Brista: A gene involved in the
speciﬁcation and differentiation of distal cephalic and
thoracic structures in Drosophila melanogaster. Rouxs Arch.
Dev. Biol., 124–132.
Sustar, A., Schubiger, G., 2005. A transient cell cycle shift in
Drosophila imaginal disc cells precedes multipotency. Cell 120,
383–393.
Treisman, J.E., Rubin, G.M., 1995. wingless inhibits morphogenetic
furrow movement in the Drosophila eye disc. Development
121, 3519–3527.
Tsai, Y.C., Sun, Y.H., 2004. Long-range effect of upd, a ligand for
Jak/STAT pathway, on cell cycle in Drosophila eye
development. Genesis 39, 141–153.
Wolff, T., 2000. Histological Techniques for the Drosophila Eye. In:
Sullivan, W. Ashburner, M.; Hawley, R.S. (Eds.), Drosophila
Protocols. Cold Spring Harbor Laboratory Press, Cold Spring
Harbor, NY.
Yoo, S.J., Huh, J.R., Muro, I., Yu, H., Wang, L., Wang, S.L., Feldman,
R.M., Clem, R.J., Muller, H.A., Hay, B.A., 2002. Hid, Rpr and Grim
negatively regulate DIAP1 levels through distinct mechanisms.
Nat. Cell Biol. 4, 416–424.

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