1 Molecular, Cellular and Developmental Biology Program, Center for Molecular
Neurobiology, Comprehensive Cancer Center, The Ohio State University,
Columbus, OH 43210, USA
2 Ohio State Biochemistry Program, Center for Molecular Neurobiology,
Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210,
USA
3 Department of Molecular Genetics, Center for Molecular Neurobiology,
Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210,
USA
Author for correspondence (e-mail:
vaessin.1{at}osu.edu)
Accepted 12 August 2003
![]() |
SUMMARY |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: IgC2 domain, Echinoid, Notch, Neurogenesis, Drosophila
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The neurogenic genes Notch (N), Delta
(Dl), Presenilin (Psn), Suppressor of
Hairless [Su(H)], mastermind (mam) and
Enhancer of split complex [E(spl)C] have been shown to
interact genetically and to function in the process of lateral inhibition
(Campos-Ortega, 1993;
Artavanis-Tsakonas et al.,
1999
). Proneural genes positively regulate the levels of the N
ligand, Dl (Haenlin et al.,
1994
). Upon binding its ligand, N undergoes Psn-dependent
processing which results in the release of the N intracellular domain
(Nicd) from the membrane (De
Strooper et al., 1999
; Struhl
and Adachi, 1998
; Struhl and
Greenwald, 1999
). Nicd translocates to the nucleus
where it forms a complex with the sequence-specific DNA-binding protein, Su
(H) (Fortini and Artavanis-Tsakonas,
1994
; Furukawa et al.,
1992
; Schweisguth and
Posakony, 1992
; Tamura et al.,
1995
) and Mam (Petcherski and
Kimble, 2000
), a transcriptional co-activator, to activate the
expression of multiple genes of the E(spl)C
(Bailey and Posakony, 1995
;
Furukawa et al., 1995
;
Lecourtois and Schweisguth,
1995
). This gene complex [E(spl)m8, E(spl)m7, E(spl)m5,
E(spl)m3, E(spl)m
, E(spl)m
and E(spl)mß]
encodes seven closely related proteins of the bHLH family of transcription
factors (Delidakis and Artavanis-Tsakonas,
1992
; Klämbt et al.,
1989
; Knust et al.,
1992
). E(spl) bHLH proteins act as transcriptional repressors in a
complex with the co-repressor protein Groucho
(Delidakis and Artavanis-Tsakonas,
1992
; Fisher and Caudy,
1998
) and downregulate achaete and scute
expression leading to suppression of neural cell fate in the cell receiving
the signal (Heitzler et al.,
1996a
).
Notch signaling pathway-mediated lateral inhibition is utilized again
during the formation of the adult peripheral nervous system (PNS) during
larval development. In the larval wing discs, proneural clusters composed of
20-30 cells are established (Campuzano and
Modolell, 1992; Modolell,
1997
). The Notch signaling pathway limits sensory organ precursor
(SOP) cell fate to one or two cells within a proneural cluster
(Artavanis-Tsakonas et al.,
1995
). The SOP gives rise to the adult external sensory organ or
bristle, which is composed of four cells (neuron, sheath cell, socket cell and
hair cell) (Bodmer et al.,
1989
; Hartenstein and
Posakony, 1989
). Disruption of the Notch signaling pathway results
in specification of additional SOPs, often resulting in the generation of
extra sensory bristles (Dietrich and
Campos-Ortega, 1984
;
Hartenstein and Posakony,
1990
; Schweisguth et al.,
1996
).
Neurogenic gene function is not limited to neural cell fate suppression.
Requirement for neurogenic gene function has been shown for the development of
other tissues, including eye, segmented appendages such as leg, mesoderm,
muscle, somatogastric nervous system, wing and during oogenesis
(Artavanis-Tsakonas et al.,
1995).
Echinoid (Ed) is a transmembrane (TM) cell adhesion molecule with seven
Immunoglobulin (Ig) C2 domains (Williams
and Barclay, 1988), two Fibronectin type III domains
(Hynes, 1986
) and a TM,
followed by a 315 amino acid intracellular domain with no identifiable
structural or functional domain (Bai et
al., 2001
). Ed has been shown to act as a negative regulator of
the EGFR signaling pathway during photoreceptor development in the larval eye
disc (Bai et al., 2001
).
Neuroglian has been identified as an activating ligand for the antagonistic
effect of Ed on the EGFR signaling pathway
(Islam et al., 2003
). Here we
report on the neurogenic phenotype of echinoid (ed) mutants.
Analysis of embryonic lethal alleles of ed reveals hyperplasia of the
central nervous system (CNS) at the expense of the epidermal structures.
Furthermore, we show that ed function is required for proper
morphogenesis of wing and leg, as well as for the specification of the proper
number of adult sensory bristles (macrochaetae and microchaetae). ed
phenotypes are suppressed by increasing N pathway activity [by overexpressing
Nact or E(spl)m7] and are enhanced by mutations in Dl or
reduction of E(spl)C activity. Thus ed functions
synergistically with the Notch signaling pathway during the processes of
neural cell fate specification and wing development.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
EMS mutagenesis
EMS mutagenesis was performed as described in Vaessin and Campos-Ortega
(Vaessin and Campos-Ortega,
1987). ed alleles were isolated in a cn bw
background based on lethality in transheterozygosity over
ed2B8 at 29°C.
Molecular biology
The ed cDNA clone LD2669 was sequenced to confirm that it
contains the entire predicted ed ORF. EdExtra was generated
via PCR, using LD2669 as template. EdExtra contains the entire Ed
extracellular region, the entire predicted TM region and an additional 11
amino acids after the predicted TM domain. Thus, EdExtra contains amino acids
1-1028. EdExtra coding region was inserted into the pUAST
transformation vector (Brand and Perrimon,
1993). pUAST-EdExtra construct was sequenced and
transgenic lines were generated by P-element-mediated transformation
(Spradling and Rubin, 1982
).
Thirteen independent UAS-EdExtra fly lines were obtained. Five lines
were further characterized. All five lines produce comparable ectopic
expression phenotypes.
The ORF of the edm1 and edts
alleles were analyzed by direct sequencing of PCR products. Genomic DNA was
isolated as described in Schlag and Wassarman
(Schlag and Wassarman, 1999).
Automated sequencing was performed at the Center for Molecular Neurobiology
DNA Sequencing Facility (Ohio State University).
Immunohistochemistry and histology
In situ hybridization to whole-mount embryos was performed as described
previously (Vaessin et al.,
1991), using digoxigenin-labeled antisense and sense RNA probes.
The following antibodies were used for immunohistochemistry: Rabbit-anti-HRP
(1:3000, Jackson Laboratories), Goat-anti-rabbit (1:3000, Jackson
Laboratories), Rabbit-anti-deadpan (Bier et
al., 1992
) and monoclonal Mouse-anti-beta-Galactosidase (Promega).
Two different anti-Ed sera were generated in this study. Polyclonal antibodies
were raised (AnimalPharm Services, Healdsburg, CA) against a His-tag fusion
protein corresponding to the N-terminal 60 amino acids (in Rabbits) and
against a His-tag fusion protein corresponding to the C-terminal 200 amino
acids (in guinea pigs). Both anti-Ed Extracellular and anti-Ed Intracellular
give a similar embryonic expression pattern for Ed. The specificity of both
anti-Ed sera was verified in homozygous Df(2L)ed1 and
ed2B8 embryos. Anti-Ed intracellular antibody signal was
amplified using biotin-conjugated secondary antibody and Fluorescein Avidin D
(Vectashield). Both light microscopy and confocal microscopy (BioRad MRC 1024)
was employed for immunohistological analysis. Cuticle preparations were
performed as described in Vaessin and Campos-Ortega
(Vaessin and Campos-Ortega,
1987
). Scanning electron micrographs (SEM) as described in Kimmel
et al. (Kimmel et al., 1990
)
as well as standard stereo dissection microscopy were utilized for analysis
and documentation of adult phenotypes.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
Immunostaining of homozygous (ed2B8,
ed3C2 and edm1) or transheterozygous
ed mutant embryos [Df(2L)ed1/ed2B8,
ed2B8/edm1, ed2B8/edts, and
ed2B8/ed3C2] with anti-HRP antibody,
which recognizes all neuronal cells of the CNS and PNS
(Jan and Jan, 1982), reveals
hyperplasia of the CNS. The observed hyperplasia ranges from mild bulges in
the CNS to an increase in the size of the entire CNS.
Fig. 2 shows an intermediate
phenotype (Fig. 2A,B). Analysis
of ed mutant embryos with antibodies against a neural precursor
marker, Deadpan (Bier et al.,
1992
), shows that the increase in the number of neurons is
preceded by an increase in the number of neural precursors
(Fig. 2E,F). The enlargement of
the CNS is accompanied by a parallel loss of epithelium, manifested as loss of
cuticle, from the ventral and procephalic regions of the embryo. The cuticular
defects range from a fusion of denticle belts to a complete absence of ventral
and ventrolateral cuticle, as well as procephalic cuticle
(Fig. 2C,D and data not shown).
The ed mutant phenotype is reminiscent of the phenotypes displayed by
loss of function mutations of neurogenic genes that are part of the Notch
signaling pathway (Lehmann et al.,
1983
).
|
|
|
Activation of the Notch signaling pathway results in suppression of
neuronal cell fate (Bray,
1998; Greenwald,
1998
). Overexpression of the intracellular region of N
(Nact) results in a dominant activated phenotype
(Fortini et al., 1993
;
Rebay et al., 1993
).
Accordingly, when Nact is expressed in embryos using the
Kr-GAL4 driver, an almost complete loss of neurons in parasegments
4-6 (Kr expression domain) is detected
(Lieber et al., 1993
)
(Fig. 5C,G). In contrast,
edts/ed2B8 transheterozygous embryos, grown at
the restrictive temperature of 29°C, show a phenotype opposite to that
caused by ectopic Nact expression. Here, hyperplasia of the CNS
with local bulging of the ventral nerve cord is evident
(Fig. 5B,F). Reduced
ed activity results in a strong suppression of the Nact
overexpression phenotype, as is evident in the CNS of UASNact:
edts/ed2B8; Kr-GAL4/+ embryos
(Fig. 5D,H). Hence, reduction
of ed activity can compensate for ectopic Notch signaling pathway
activity.
|
We also analyzed the ability of the dominant-negative EdExt protein to
functionally interact with Notch signaling pathway genes. In these experiments
EdExt was ectopically expressed using the Eq-GAL4 driver.
Eq-GAL4 mediates expression in the anterior region of the presumptive
notum in the wing disc, with a stronger expression in the anterior midline
region (Pi et al., 2001).
UAS-EdExt/+; Eq-GAL4/+ flies exhibit a slight increase in the number
of microchaetae (Fig. 6B).
Overexpression of full-length Dl has been shown to cause an increase in the
number of sensory organs (Doherty et al.,
1997
) (Fig. 6C). It
has been argued that this is because of the ability of Dl to autonomously
inhibit N signal reception in Dl-expressing cells. Hence, when all cells of
the proneural clusters express high levels of Dl, N signal reception would be
inhibited, causing an increase in the number of sensory organs
(Doherty et al., 1996
;
Doherty et al., 1997
).
Simultaneous overexpression of Dl and EdExt using the Eq-GAL4 driver
resulted in a dramatic increase in the number of microchaetae that exceeds the
additive combination of the respective phenotypes
(Fig. 6D). Hence,
dominant-negative EdExt causes increased reduction in Notch signaling
pathway-mediated lateral inhibition caused by ectopic expression of Dl.
Accordingly, an increase in the activity of the Notch signaling pathway should
suppresses the phenotype caused by EdExt overexpression. Flies overexpressing
EdExt in the pnr expression domain (UASEdExt/+; pnr-GAL4/+)
show extra sensory organs (Fig.
4F, Fig. 6F).
Ectopic expression of E(spl)m7, a downstream target of an activated Notch
signaling pathway, suppresses sensory organ specification resulting in the
absence of bristles (Ligoxygakis et al.,
1999
). Flies expressing ectopic EdExt and E(spl)m7 simultaneously
are indistinguishable from those expressing only E(spl)m7 ectopically
(Fig. 6H), implying that
increasing the activity of Notch signaling pathway can compensate for reduced
Ed activity.
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
ed RNA and protein expression during early neurogenesis indicates that ed gene products become restricted to the neuroectodermal cell layer, whereas no ed products are detectable in the delaminated neuroblasts. The dynamics of ed RNA and protein distribution during neuroblast delamination implies that ed function might be required in cells that remain in the ectodermal cell layer. In such a scenario, similar to N, ed function would be required in the cells receiving the lateral inhibitory signal. However, it should be noted that at the time when the differential distribution of ed RNA and protein becomes detectable, the neuroblast segregation has already been initiated.
Ed expression during embryogenesis is dynamic and seen in many developing
organ systems. The widespread expression of ed indicates that
ed might be required for the development of multiple organs. Indeed,
analysis of the trachea and muscles in ed mutant embryos reveals
defects in the proper formation of these organ systems (data not shown). The
requirement of ed for normal development of multiple tissues is not
limited to embryogenesis. Adult flies with reduced ed activity show
defects in leg, wing and eye development
(Bai et al., 2001;
Islam et al., 2003
). A similar
widespread expression and requirement in multiple organs has also been
observed for the Notch signaling pathway during Drosophila
development (Artavanis-Tsakonas et al.,
1999
).
The ectopically expressed extracellular domain of Ed has
dominant-negative activity
Ed protein missing its intracellular region interferes with the process of
lateral inhibition, as overexpression of EdExt in the developing wing disc
results in an increase in the number of macrochaetae and microchaetae.
Additional phenotypes include the irregular thickening of wing vein II and
infrequent notching of the wing margin. These phenotypes are similar to those
seen upon reduced ed function. Thus, ectopic expression of EdExt
interferes with the function of endogenous Ed. A dominant-negative activity of
the extracellular portion is not unusual for receptors that bind to ligands
and then transduce a signal intracellularly
(Rebay et al., 1993). Thus, it
is possible that the EdExt competes with the WT Ed for a limited amount of
ligand. Because EdExt is missing its intracellular region, its binding to the
ligand may have no functional consequence other than limiting the amount of
available ligand. The ability of the extracellular domain to act as a
dominant-negative molecule and the observation that the temperature-sensitive
allele of ed has a mutation associated with Ig C2 domain V implies
that the interaction of the extracellular domain with a putative ligand is an
essential component of Ed function. Two isoforms of Neuroglian (Nrg) have
recently been identified as activating ligands for the antagonistic effect of
Ed on the EGFR pathway in the eye disc
(Islam et al., 2003
). Both
isoforms (Nrg180 and Nrg167) are expressed in the wing
disc (Hortsch et al., 1990
)
and thus overlap in their expression with Ed. It has yet to be determined
whether Nrg also functions as a ligand for Ed during sensory organ
development. Ed has been shown to act as a homophilic cell adhesion molecule
(Islam et al., 2003
) (A.A.,
S.C. and H.V., unpublished). In the eye disc, it has been shown that the
Nrg-mediated heterophilic activity of Ed in repressing the EGFR signaling
pathway is redundant with the homophilic activity of Ed
(Islam et al., 2003
). Thus, it
is possible that the dominant-negative construct interferes with Ed activity
by competing for homophilic binding.
Ed interacts synergistically with the Notch signaling pathway
Ectopic expression of an activated form of N results in suppression of
neuronal specification (Lieber et al.,
1993; Rebay et al.,
1993
; Struhl et al.,
1993
). In contrast, reduced ed gene activity results in
increased specification of neurons. Ectopic expression of Nact in
ed2B8/edts embryos results in a near WT nervous
system. The observation of compensating, as opposed to an epistatic phenotype,
does not support the formulation of a straightforward epistatic relationship
between ed and N gene function. Rather, although both WT
N and ed have a similar antineurogenic function during
neurogenesis, they might be acting in functionally synergistic, yet possibly
parallel regulatory pathways.
The observation of dosage-sensitive interactions between mutations in two genes can also be indicative of closely related roles. We have observed dosage-sensitive interactions between ed and Dl and ed and E(spl). The mild wing phenotype exhibited by edm1/edts flies raised at 25°C is enhanced by loss of one copy of Dl. Similarly, the wing phenotype of E(spl)8D06/+ flies is enhanced by reduction of Ed activity. These observations imply that, in the wing disc also, the Notch signaling pathway and ed are acting synergistically.
Genetic interaction between ed and the Notch signaling pathway is
also observed during the development of the adult PNS. Ectopic expression of
EdExt results in specification of extra macrochaetae and microchaetae.
Overexpression of Dl results in an increase in the number of sensory bristles
(Doherty et al., 1997).
Simultaneous ectopic expression of EdExt and Dl has a phenotype much stronger
than what would be the result of additive combination of the individual
phenotypes. The EdExt protein interferes with the activity of endogenous Ed
and the decrease in Ed activity increases the neurogenic phenotype caused by
Dl overexpression. These observations imply that Ed acts in concert with Dl.
An epistatic interaction was also observed with E(spl)m7. Ectopic expression
of E(spl)m7 completely suppressed the extra bristles phenotype obtained upon
EdExt expression. The complete suppression of the dominant-negative phenotype
would imply that E(spl)m7 functions downstream to the ed. However, it
is possible that this suppression is a result of the strong antineurogenic
activity of E(spl)m7. Although it is presently not clear whether ed
and the genes of the Notch signaling pathway function in the same or parallel
pathway, our observations establish that ed and the Notch signaling
pathway genes act synergistically in both embryonic and postembryonic
development.
Ed, Fred and the N and EGFR signaling pathway
Ed has previously been shown to be a negative regulator of the EGFR
pathway. ed mutations enhance the rough eye phenotype of
ElpB1, a gain-of-function EGFR allele, and
ed genetically interacts with several components of the EGFR pathway
during eye development. As a consequence, ed mutant phenotypes
include the generation of extra photoreceptor and cone cells
(Bai et al., 2001;
Rawlins et al., 2003
;
Spencer and Cagan, 2003
). We
have shown that ed mutations result in neural hyperplasia in the
embryo and the formation of extra sensory organs on the notum of adult flies,
and that ed, in these processes, interacts synergistically with the
Notch signaling pathway. We have recently described an Ed paralog, Fred, and
have shown that Fred is required to suppress SOP specification and is required
for proper eye development (Chandra et
al., 2003
). Similar to ed, fred interacts synergistically
with the Notch signaling pathway during SOP specification and also during eye
development. fred also interacts with the EGFR pathway. Furthermore,
ed and fred show a dosage-sensitive interaction during eye
development, indicating that the two genes function in close concert
(Chandra et al., 2003
). Hence,
ed and fred define a subgroup of two closely related
IgC2-type TM proteins that interact synergistically with the Notch signaling
pathway and antagonistically with the EGFR pathway.
Putative roles of a cell adhesion protein in neuronal precursor
specification
Our data point to a role of Ed in the cell-cell communication processes
that lead to the selection of the future neural precursor from the proneural
cluster. In this process, Ed functions synergistically with the Notch
signaling pathway. In this role Ed might be part of the cell-cell
communication process itself. However, keeping in mind its cell-cell adhesion
function, it could be argued that Ed may also be involved in the execution of
the developmental decisions that result from cell-cell communication. In this
scenario downregulation of ed expression in the future neuroblast may
contribute to neuroblast delamination, whereas continued ed
expression in the future epidermal precursors maintains cell adhesion and
stabilizes their fate. Thus, Ed might be functioning at the level of cell-cell
communication and at the level of coordinating cell-cell signaling with
morphogenesis.
Note added in proof
A paper by Escudero et al. (Escudero et
al., 2003) with similar conclusions appears in this issue.
![]() |
ACKNOWLEDGMENTS |
---|
![]() |
Footnotes |
---|
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Artavanis-Tsakonas, S., Matsuno, K. and Fortini, M. E. (1995). Notch signaling. Science 268,225 -232.[Medline]
Artavanis-Tsakonas, S., Rand, M. D. and Lake, R. J.
(1999). Notch signaling: cell fate control and signal integration
in development. Science
284,770
-776.
Bai, J., Chiu, W., Wang, J., Tzeng, T., Perrimon, N. and Hsu,
J. (2001). The cell adhesion molecule Echinoid defines a new
pathway that antagonizes the Drosophila EGF receptor signaling
pathway. Development
128,591
-601.
Bailey, A. M. and Posakony, J. W. (1995). Suppressor of hairless directly activates transcription of enhancer of split complex genes in response to Notch receptor activity. Genes Dev. 9,2609 -2622.[Abstract]
Bertrand, N., Castro, D. S. and Guillemot, F. (2002). Proneural genes and the specification of neural cell types. Nat. Rev. Neurosci. 3, 517-530.[CrossRef][Medline]
Bier, E., Vaessin, H., Shepherd, S., Lee, K., McCall, K., Barbel, S., Ackerman, L., Carretto, R., Uemura, T. and Grell, E. (1989). Searching for pattern and mutation in the Drosophila genome with a P-lacZ vector. Genes Dev. 3,1273 -1287.[Abstract]
Bier, E., Vaessin, H., Younger-Shepherd, S., Jan, L. Y. and Jan, Y. N. (1992). deadpan, an essential pan-neural gene in Drosophila, encodes a helix-loop-helix protein similar to the hairy gene product. Genes Dev. 6,2137 -2151.[Abstract]
Bodmer, R., Carretto, R. and Jan, Y. N. (1989). Neurogenesis of the peripheral nervous system in Drosophila embryos: DNA replication patterns and cell lineages. Neuron 3, 21-32.[Medline]
Brand, A. H. and Perrimon, N. (1993). Targeted
gene expression as a means of altering cell fates and generating dominant
phenotypes. Development
118,401
-415.
Bray, S. (1998). Notch signalling in Drosophila: three ways to use a pathway. Semin. Cell Dev. Biol. 9,591 -597.[CrossRef][Medline]
Campos-Ortega, J. A. (1993). Early neurogenesis in Drosophila melanogaster. In The Development of Drosophila melanogaster. Vol. 2 (ed. M. Bate and A. Martinez Arias), pp. 1091-1129. Cold Spring Harbor, NY, USA: Cold Spring Harbor Laboratory Press.
Campuzano, S. and Modolell, J. (1992). Patterning of the Drosophila nervous system: the achaete-scute gene complex. Trends Genet. 8, 202-208.[Medline]
Chandra, S., Ahmed, A. and Vaessin, H. (2003). The Drosophila IgC2 domain protein Friend-of-Echinoid, a paralogue of Echinoid, limits the number of sensory organ precursors in the wing disc and interacts with the Notch signaling pathway. Dev. Biol. 256,302 -316.[CrossRef][Medline]
De Strooper, B., Annaert, W., Cupers, P., Saftig, P., Craessaerts, K., Mumm, J. S., Schroeter, E. H., Schrijvers, V., Wolfe, M. S. and Ray, W. J. et al. (1999). A presenilin-1-dependent gamma-secretase-like protease mediates release of Notch intracellular domain. Nature 398,518 -522.[CrossRef][Medline]
Delidakis, C. and Artavanis-Tsakonas, S. (1992). The Enhancer of split [E(spl)] locus of Drosophila encodes seven independent helix-loop-helix proteins. Proc. Natl. Acad. Sci. USA 89,8731 -8735.[Abstract]
Dietrich, U. and Campos-Ortega, J. A. (1984). The expression of neurogenic loci in imaginal epidermal cells of Drosophila melanogaster. J. Neurogenet. 1, 315-332.[Medline]
Doherty, D., Feger, G., Younger-Shepherd, S., Jan, L. Y. and Jan, Y. N. (1996). Delta is a ventral to dorsal signal complementary to Serrate, another Notch ligand, in Drosophila wing formation. Genes Dev. 10,421 -434.[Abstract]
Doherty, D., Jan, L. Y. and Jan, Y. N. (1997).
The Drosophila neurogenic gene big brain, which encodes a
membrane-associated protein, acts cell autonomously and can act
synergistically with Notch and Delta. Development
124,3881
-3893.
Escudero, L. M., Wei, S.-Y., Chin, W.-H., Modolell, J. and Hsu,
J.-C. (2003). Echinoid synergizes with the Notch signaling
pathway in Drosophila mesothorax bristle patterning.
Development 130,6305
-6316.
Fisher, A. L. and Caudy, M. (1998). Groucho
proteins: transcriptional corepressors for specific subsets of DNA-binding
transcription factors in vertebrates and invertebrates. Genes
Dev. 12,1931
-1940.
Fortini, M. E. and Artavanis-Tsakonas, S. (1994). The suppressor of hairless protein participates in notch receptor signaling. Cell 79,273 -282.[Medline]
Fortini, M. E., Rebay, I., Caron, L. A. and Artavanis-Tsakonas, S. (1993). An activated Notch receptor blocks cell-fate commitment in the developing Drosophila eye. Nature 365,555 -557.[CrossRef][Medline]
Furukawa, T., Maruyama, S., Kawaichi, M. and Honjo, T. (1992). The Drosophila homolog of the immunoglobulin recombination signal-binding protein regulates peripheral nervous system development. Cell 69,1191 -1197.[Medline]
Furukawa, T., Kobayakawa, Y., Tamura, K., Kimura, K., Kawaichi, M., Tanimura, T. and Honjo, T. (1995). Suppressor of hairless, the Drosophila homologue of RBP-J kappa, transactivates the neurogenic gene E(spl)m8. Jpn. J. Genet. 70,505 -524.[Medline]
Greenwald, I. (1998). LIN-12/Notch signaling:
lessons from worms and flies. Genes Dev.
12,1751
-1762.
Haenlin, M., Kunisch, M., Kramatschek, B. and Campos-Ortega, J. A. (1994). Genomic regions regulating early embryonic expression of the Drosophila neurogenic gene Delta. Mech. Dev. 47,99 -110.[CrossRef][Medline]
Hartenstein, V. and Posakony, J. W. (1989). Development of adult sensilla on the wing and notum of Drosophila melanogaster. Development 107,389 -405.[Abstract]
Hartenstein, V. and Posakony, J. W. (1990). A dual function of the Notch gene in Drosophila sensillum development. Dev. Biol. 142,13 -30.[Medline]
Heitzler, P., Bourouis, M., Ruel, L., Carteret, C. and Simpson,
P. (1996a). Genes of the Enhancer of split and achaete-scute
complexes are required for a regulatory loop between Notch and Delta during
lateral signalling in Drosophila. Development (Suppl.)
122,161
-171.
Heitzler, P., Haenlin, M., Ramain, P., Calleja, M. and Simpson,
P. (1996b). A genetic analysis of pannier, a gene necessary
for viability of dorsal tissues and bristle positioning in Drosophila.Genetics 143,1271
-1286.
Hortsch, M., Bieber, A. J., Patel, N. H. and Goodman, C. S. (1990). Differential splicing generates a nervous system-specific form of Drosophila neuroglian. Neuron 4, 697-709.[Medline]
Hynes, R. O. (1986). Fibronectins. Sci. Am. 254,42 -51.[Medline]
Islam, R., Wei, S. Y., Chiu, H., Hortsch, M. and Hsu, J. C.
(2003). Neuroglian activates Echinoid to antagonize the
Drosophila EGF receptor signaling pathway.
Development 130,2051
-2059.
Jan, L. Y. and Jan, Y. N. (1982). Antibodies to horseradish peroxidase as specific neuronal markers in Drosophila and in grasshopper embryos. Proc. Natl. Acad. Sci. USA 79,2700 -2704.[Abstract]
Jan, Y. N. and Jan, L. Y. (1993). The peripheral nervous system. In The Development of Drosophila melanogaster. Vol. 2 (ed. M. Bate and A. Martinez Arias), pp. 1207-1244. Cold Spring Harbor, NY, USA: Cold Spring Harbor Laboratory Press.
Kimmel, B. E., Heberlein, U. and Rubin, G. M. (1990). The homeo domain protein rough is expressed in a subset of cells in the developing Drosophila eye where it can specify photoreceptor cell subtype. Genes Dev. 4, 712-727.[Abstract]
Klämbt, C., Knust, E., Tietze, K. and Campos-Ortega, J. A. (1989). Closely related transcripts encoded by the neurogenic gene complex enhancer of split of Drosophila melanogaster.EMBO J. 8,203 -210.[Abstract]
Knust, E., Bremer, K. A., Vassin, H., Ziemer, A., Tepass, U. and Campos-Ortega, J. A. (1987). The enhancer of split locus and neurogenesis in Drosophila melanogaster. Dev. Biol. 122,262 -273.[Medline]
Knust, E., Schrons, H., Grawe, F. and Campos-Ortega, J. A.
(1992). Seven genes of the Enhancer of split complex of
Drosophila melanogaster encode helix-loop-helix proteins.
Genetics 132,505
-518.
Lecourtois, M. and Schweisguth, F. (1995). The neurogenic suppressor of hairless DNA-binding protein mediates the transcriptional activation of the enhancer of split complex genes triggered by Notch signaling. Genes Dev. 9,2598 -2608.[Abstract]
Lehmann, R., Jimenez, F., Dietrich, U. and Campos-Ortega, J. A. (1983). On the phenotype and development of mutants of early neurogenesis in Drosophila melanogaster. Wilhelm Roux's Arch. Dev. Biol. 190,226 -229.
Lieber, T., Kidd, S., Alcamo, E., Corbin, V. and Young, M. W. (1993). Antineurogenic phenotypes induced by truncated Notch proteins indicate a role in signal transduction and may point to a novel function for Notch in nuclei. Genes Dev. 7,1949 -1965.[Abstract]
Ligoxygakis, P., Bray, S. J., Apidianakis, Y. and Delidakis,
C. (1999). Ectopic expression of individual E(spl) genes has
differential effects on different cell fate decisions and underscores the
biphasic requirement for notch activity in wing margin establishment in
Drosophila. Development
126,2205
-2214.
Modolell, J. (1997). Patterning of the adult peripheral nervous system of Drosophila. Perspect. Dev. Neurobiol. 4,285 -296.[Medline]
Modolell, J. and Campuzano, S. (1998). The achaete-scute complex as an integrating device. Int. J. Dev. Biol. 42,275 -282.[Medline]
Petcherski, A. G. and Kimble, J. (2000). Mastermind is a putative activator for Notch. Curr. Biol. 10,R471 -473.[CrossRef][Medline]
Pi, H., Wu, H. J. and Chien, C. T. (2001). A dual function of phyllopod in Drosophila external sensory organ development: cell fate specification of sensory organ precursor and its progeny. Development 128,2699 -2710.[Medline]
Rawlins, E. L., White, N. M. and Jarman, A. P.
(2003). Echinoid limits R8 photoreceptor specification by
inhibiting inappropriate EGF receptor signalling within R8 equivalence groups.
Development 130,3715
-3724.
Rebay, I., Fehon, R. G. and Artavanis-Tsakonas, S. (1993). Specific truncations of Drosophila Notch define dominant activated and dominant negative forms of the receptor. Cell 74,319 -329.[Medline]
Schlag, E. M. and Wassarman, D. A. (1999). Identifying mutations in Drosophila genes by direct sequencing of PCR products. BioTechniques 27,262 -264.[Medline]
Schweisguth, F., Gho, M. and Lecourtois, M. (1996). Control of cell fate choices by lateral signaling in the adult peripheral nervous system of Drosophila melanogaster. Dev. Genet. 18,28 -39.[CrossRef][Medline]
Schweisguth, F. and Posakony, J. W. (1992). Suppressor of Hairless, the Drosophila homolog of the mouse recombination signal-binding protein gene, controls sensory organ cell fates. Cell 69,1199 -1212.[Medline]
Spencer, S. A. and Cagan, R. L. (2003).
Echinoid is essential for regulation of Egfr signaling and R8 formation during
Drosophila eye development. Development
130,3725
-3733.
Spradling, A. C. and Rubin, G. M. (1982). Transposition of cloned P elements into Drosophila germ line chromosomes. Science 218,341 -347.[Medline]
Struhl, G. and Adachi, A. (1998). Nuclear access and action of notch in vivo. Cell 93,649 -660.[Medline]
Struhl, G. and Greenwald, I. (1999). Presenilin is required for activity and nuclear access of Notch in Drosophila.Nature 398,522 -525.[CrossRef][Medline]
Struhl, G., Fitzgerald, K. and Greenwald, I. (1993). Intrinsic activity of the Lin-12 and Notch intracellular domains in vivo. Cell 74,331 -345.[Medline]
Tamura, K., Taniguchi, Y., Minoguchi, S., Sakai, T., Tun, T., Furukawa, T. and Honjo, T. (1995). Physical interaction between a novel domain of the receptor Notch and the transcription factor RBP-J kappa/Su(H). Curr. Biol. 5,1416 -1423.[Medline]
Vaessin, H. and Campos-Ortega, J. A. (1987).
Genetic analysis of Delta, a neurogenic gene of Drosophila
melanogater. Genetics 116,433
-445.
Vaessin, H., Grell, E., Wolff, E., Bier, E., Jan, L. Y. and Jan, Y. N. (1991). prospero is expressed in neuronal precursors and encodes a nuclear protein that is involved in the control of axonal outgrowth in Drosophila. Cell 67,941 -953.[Medline]
Williams, A. F. and Barclay, A. N. (1988). The immunoglobulin superfamily - domains for cell surface recognition. Annu. Rev. Immunol. 6,381 -405.[CrossRef][Medline]