In the developing Drosophila eye, individual cell fates are specified when general signaling mechanisms are interpreted in the context of cell-specific transcription factors. Lozenge, a Runt/AML1/CBFA1-like transcription factor, determines the fates of a number of neuronal and non-neuronal cells by regulating the expression of multiple fate-determining transcription factors. The Lozenge protein is expressed in the nuclei of the cells that it patterns and also in their undifferentiated precursors. An enhancer element located within the second intron of the lozenge gene is responsible for its eye-specific expression. Lozenge is not itself a cell-specific transcription factor, rather it prepatterns the eye disc by positioning cell-specific factors in their appropriate locations.

REFERENCES

Batterham
P.
,
Crew
J. R.
,
Sokac
A. M.
,
Andrews
J. R.
,
Pasquini
G. M. F.
,
Davies
A. G.
,
Stocker
R. F.
,
Pollock
J. A.
(
1996
)
Genetic analysis of the lozenge gene complex in Drosophila melanogaster: Adult visual system phenotypes.
J. Neurogen
10
,
193
220
Brunner
D.
,
Ducker
K.
,
Oellers
N.
,
Hafen
E.
,
Scholz
H.
,
Klambt
C.
(
1994
)
The ETS domain protein Pointed-P2 is a target of MAP kinase in the Sevenless signal transduction pathway.
Nature
370
,
386
389
Daga
A.
,
Karlovich
C. A.
,
Dumstrei
K.
,
Banerjee
U.
(
1996
)
Patterning of cells in the Drosophila eye by Lozenge, which shares homologous domains with AML1.
Genes Dev
10
,
1194
1205
de Nooij
J. C.
,
Hariharan
I. K.
(
1995
)
Uncoupling cell fate determination from patterned cell division in the Drosophila eye.
Science
270
,
983
985
Dokucu
M. E.
,
Zipursky
S. L.
,
Cagan
R. L.
(
1996
)
Atonal, Rough and the resolution of proneural clusters in the developing Drosophila retina.
Development
122
,
4139
4147
Freeman
M.
(
1996
)
Reiterative use of the EGF receptor triggers differentiation of all cell types in the Drosophila eye.
Cell
87
,
651
660
Fu
W.
,
Noll
M.
(
1997
)
The Pax2 homolog sparkling is required for development of cone and pigment cells in the Drosophila eye.
Genes Dev
11
,
2066
2078
Geyer
P. K.
,
Green
M. M.
,
Corces
V. G.
(
1990
)
Tissue-specific transcriptional enhancers may act in trans on the gene located in the homologous chromosome: the molecular basis of transvection in Drosophila.
EMBO J
9
,
2247
2256
Giese
K.
,
Kingsley
C.
,
Kirshner
J. R.
,
Grosschedl
R.
(
1995
)
Assembly and function of a TCR alpha enhancer complex is dependent on LEF-1-induced DNA bending and multiple protein-protein interactions.
Genes Dev
9
,
995
1008
Green
M. M.
,
Green
K. C.
(
1949
)
Crossing-over between alleles at the lozenge locus in Drosophila melanogaster.
Proc. Natl. Acad. Sci. USA
35
,
586
591
Higashijima
S.
,
Kojima
T.
,
Michiue
T.
,
Ishimaru
S.
,
Emori
T.
,
Saigo
K.
(
1992
)
Dual Bar homeo box genes of Drosophila required in two photoreceptor cells, R1 and R6, and primary pigment cells for normal eye development.
Genes Dev
6
,
50
60
Hou
X. S.
,
Goldstein
E. S.
,
Perrimon
N.
(
1997
)
Drosophila Jun relays the Jun amino-terminal kinase signal transduction pathway to the Decapentaplegic signal transduction pathway in regulating epithelial cell sheet movement.
Genes Dev
11
,
1728
1737
Ito
Y.
(
1997
)
The Runt protein and its companion PEBP2: a close link between this transcription factor and AML.
Leukemia
3
,
279
280
Jarman
A. P.
,
Sun
Y.
,
Jan
L. Y.
,
Jan
Y. N.
(
1995
)
Role of the proneural gene, atonal, in formation of the Drosophila chordotonal organs and photoreceptors.
Development
121
,
2019
2030
Kauffman
R. C.
,
Li
S.
,
Gallagher
P. A.
,
Zhang
J.
,
Carthew
R. W.
(
1996
)
Ras1 signaling and transcriptional competence in the R7 cell of Drosophila.
Genes Dev
10
,
2167
2178
Kockel
L.
,
Zeitlinger
J.
,
Staszewski
L. M.
,
Mlodzik
M.
,
Bohmann
D.
(
1997
)
Jun in Drosophila development: redundant and nonredundant functions and regulation by two MAPK signal transduction pathways.
Genes Dev
11
,
1748
1758
Kumar
J.
,
Moses
K.
(
1997
)
Transcription factors in eye development: a gorgeous mosaic?.
Genes Dev
11
,
2023
2028
Leiserson
W. M.
,
Bonini
N. M.
,
Benzer
S.
(
1994
)
Transvection at the eyes absent gene of Drosophila.
Genetics
138
,
1171
1179
Li
S.
,
Li
Y.
,
Carthew
R. W.
,
Lai
Z.-. C.
(
1997
)
Photoreceptor cell differentiation requires regulated proteolysis of the transcriptional repressor Tramtrack.
Cell
90
,
469
478
Martínez-Laborda
A.
,
González-Reyes
A.
,
Morata
G.
(
1992
)
Trans regulation in the Ultrabithorax gene of Drosophila: alterations in the promoter enhance transvection.
EMBO J
11
,
3645
3652
Mlodzik
M.
,
Hiromi
Y.
,
Weber
U.
,
Goodman
C. S.
,
Rubin
G. M.
(
1990
)
The Drosophilaseven-up gene, a member of the steroid receptor gene superfamily, controls photoreceptor cell fates.
Cell
60
,
211
224
Muller
H. P.
,
Schaffner
W.
(
1990
)
Transcriptional enhancers can act in trans.
Trends Genet
6
,
300
304
Okuda
T.
,
van Deursen
J.
,
Hiebert
S. W.
,
Grosveld
G.
,
Downing
J. R.
(
1996
)
AML1, the target of multiple chromosomal translocations in human leukemia is essential for normal fetal liver hematopoiesis.
Cell
84
,
321
330
O'Neill
E. M.
,
Rebay
I.
,
Tjian
R.
,
Rubin
G. M.
(
1994
)
The activities of two Ets-related transcription factors required for Drosophila eye development are modulated by the Ras/MAPK pathway.
Cell
78
,
137
147
Quandt
K.
,
Frech
K.
,
Karas
H.
,
Wingender
E.
,
Werner
T.
(
1995
)
MatInd and MatInspector—New fast and versatile tools for detection of consensus matches in nucleotide sequence data.
Nucl. Acids Res
23
,
4878
4884
Ray
K.
,
Rodrigues
V.
(
1995
)
Cellular events during development of the olfactory sense organs in Drosophila melanogaster.
Dev. Biol
167
,
426
438
Ready
D. F.
,
Hanson
T. E.
,
Benzer
S.
(
1976
)
Development of the Drosophila retina, a neurocrystalline lattice.
Dev. Biol
53
,
217
240
Rebay
I.
,
Rubin
G. M.
(
1995
)
Yan functions as a general inhibitor of differentiation and is negatively regulated by activation of the Ras1/MAPK pathway.
Cell
81
,
857
866
Riesgo-Escovar
J. R.
,
Hafen
E.
(
1997
)
Common and distince roles of Dfos and Djun during Drosophila develoment.
Science
278
,
669
672
Riesgo-Escovar
J. R.
,
Jenni
M.
,
Fritz
A.
,
Hafen
E.
(
1996
)
The Drosophila Jun-N-terminal kinase is required for cell morphogenesis but not for DJun-dependent cell fate specification in the eye.
GenesDev
10
,
2759
2768
Rodan
G. A.
,
Harada
S.-i.
(
1997
)
The missing bone.
Cell
89
,
677
680
Rogge
R.
,
Green
P. J.
,
Urano
J.
,
Horn-Saban
S.
,
Mlodzik
M.
,
Shilo
B.
,
Hartenstein
V.
,
Banerjee
U.
(
1995
)
The role of yan in mediating the choice between cell division and differentiation.
Development
121
,
3947
3958
Stocker
F. R.
,
Gendre
N.
(
1988
)
Peripheral and central nervous system effects of lz3, a Drosophila mutant lacking basiconic antennal sensilla.
Dev. Biol
127
,
12
27
Tang
A. H.
,
Neufeld
T. P.
,
Kwan
E.
,
Rubin
G. M.
(
1997
)
PHYL acts to down-regulate TTK88, a transcriptional repressor of neuronal cell fates, by a SINA-dependent mechanism.
Cell
90
,
459
467
Tio
M.
,
Moses
K.
(
1997
)
The Drosophila TGFhomolog Spitz acts in photoreceptor recruitment in the developing retina.
Development
124
,
343
351
Tomlinson
A.
,
Ready
D. F.
(
1987
)
Neuronal differentiation in the Drosophila ommatidium.
Dev. Biol
120
,
366
376
Tsai
C.
,
Gergen
J. P.
(
1994
)
Gap gene properties of the pair-rule gene runt during Drosophila segmentation.
Development
120
,
1671
1683
Xiong
W. C.
,
Montell
C.
(
1993
)
tramtrack is a transcriptional repressor required for cell fate determination in the Drosophila eye.
Genes Dev
7
,
1085
1096
Wang
Q.
,
Stacy
T.
,
Binder
M.
,
Marin-Padilla
M.
,
Sharpe
A. H.
,
Speck
N.
(
1996
)
Disruption of the Cbfa2 gene causes necrosis and hemorrhaging in the central nervous system and blocks definitive hematopoiesis.
Proc. Natl. Acad. Sci. USA
93
,
3444
3449
Williams
J. A.
,
Paddock
S. W.
,
Vorwerk
K.
,
Carroll
S. B.
(
1994
)
Organization of wing formation and induction of a wing-patterning gene at the dorsal/ventral compartment boundary.
Nature
368
,
299
305
Wolff
T.
,
Ready
D. F.
(
1991
)
The beginning of pattern formation in the Drosophila compound eye: the morphogenetic furrow and the second mitotic wave.
Development
113
,
841
850
Wotton
D.
,
Ghysdael
J.
,
Wang
S.
,
Speck
N. A.
,
Owen
M. J.
(
1994
)
Cooperative binding of Ets-1 and core binding factor to DNA.
Mol. Cell. Biol
14
,
840
850
Zeitlinger
J.
,
Kockel
L.
,
Peverali
F. A.
,
Jackson
D. B.
,
Mlodzik
M.
,
Bohmann
D.
(
1997
)
Defective dorsal closure and loss of epidermal decapentaplegic expression in Drosophila fos mutants.
EMBO J
16
,
7393
7401
This content is only available via PDF.