Within the Drosophila embryo, the formation of many neuroblasts depends on the functions of the proneural genes of the achaete-scute complex (AS-C): achaete (ac), scute (sc) and lethal of scute (l'sc), and the gene ventral nervous system defective (vnd). Here, we show that vnd controls neuroblast formation, in part, through its regulation of the proneural genes of the AS-C. vnd is absolutely required to activate ac, sc and l'sc gene expression in proneural clusters in specific domains along the medial column of the earliest arising neuroblasts. Using ac-lacZ reporter constructs, we determined that vnd controls proneural gene expression at two distinct steps during neuroblast formation through separable regulatory regions. First, vnd is required to activate proneural cluster formation within the medial column of every other neuroblast row through regulatory elements located 3′ to ac; second, through a 5′ regulatory region, vnd functions to increase or maintain proneural gene expression in the cell within the proneural cluster that normally becomes the neuroblast. By following neuroblast segregation in vnd mutant embryos, we show that the neuroectoderm forms normally and that the defects in neuroblast formation are specific to particular proneural clusters.

Alberga
A.
,
Boulay
J.-L.
,
Kempe
E.
,
Dennefeld
C.
,
Haenlin
M.
(
1991
)
The snail gene required for mesoderm formation in Drosophila is expressed dynamically in derivatives of all three germ layers.
Development
111
,
983
992
Alonso
M.
,
Cabrera
C. V.
(
1988
)
The achaete-scute gene complex of Drosophila melanogaster comprises four homologous genes.
EMBO J
7
,
2585
2591
Artavanis-Tsakonas
S.
,
Simpson
P.
(
1991
)
Choosing a cell fate: a view from the Notch locus.
Trends Genet
7
,
403
408
Cabrera
C. V.
(
1990
)
Lateral inhibition and cell fate during neurogenesis in Drosophila: the interactions between scute, Notch and Delta.
Development
109
,
733
742
Cabrera
C. V.
,
Martinez-Arias
A.
,
Bate
M.
(
1987
)
The expression of three members of the achaete-scute complex correlates with neuroblast segregation in Drosophila.
Cell
50
,
425
433
Campos-Ortega
J. A.
,
Jan
Y. N.
(
1991
)
Genetic and molecular basis of neurogenesis in Drosophila melanogaster.
Annu. Rev. Neurosci
14
,
399
420
Chu-LaGraff
Q.
,
Doe
C.
(
1993
)
Neuroblast specification and formation regulated by wingless in the Drosophila CNS.
Science
261
,
1594
1597
Cubas
P.
,
de Celis
J. F.
,
Campuzano
S.
,
Modolell
J.
(
1991
)
Proneural clusters of achaete-scute expression and the generation of sensory organs in the Drosophila imaginal wing discs.
Genes Dev
5
,
996
1008
Dambly-Chaudiere
C.
,
Ghysen
A.
(
1987
)
Independent subpatterns of sense-organs require independent genes of the achaete-scute complex in Drosophila larvae.
Genes Dev
1
,
297
306
Doe
C.
(
1992
)
Molecular markers for identified neuroblasts and ganglion mother cells in the Drosophila central nervous system.
Development
116
,
855
863
Heitzler
P.
,
Simpson
P.
(
1991
)
The choice of cell fate in the epidermis of Drosophila.
Cell
64
,
1083
1092
Jiang
J.
,
Ip
Y. T.
,
Kosman
D.
,
Levine
M.
(
1991
)
The dorsal morphogen gradient regulates the mesoderm determinant twist in early Drosophila embryos.
Genes Dev
5
,
1881
1891
Jimenez
F.
,
Campos-Ortega
J. A.
(
1979
)
A region of the Drosophila genome necessary for CNS development.
Nature
282
,
310
312
Jimenez
F.
,
Campos-Ortega
J. A.
(
1987
)
Genes in subdivision 1B of the Drosophila melanogaster X-chromosome and their influence on neural development.
J. Neurogenetics
4
,
179
200
Jimenez
F.
,
Campos-Ortega
J. A.
(
1990
)
Defective neuroblast commitment in mutants of the achaete-scute complex and adjacent genes of D. melanogaster.
Neuron
5
,
81
89
Jimenez
F.
,
Modolell
J.
(
1993
)
Neural fate specification in Drosophila.
Cur. Opin. Gen. Dev
3
,
626
632
Kosman
D.
,
Ip
Y. T.
,
Levine
M.
,
Aroroa
K.
(
1991
)
Establishment of the mesoderm-neuroectoderm boundary in the Drosophila embryo.
Science,
254
,
118
122
Martin-Bermudo
M. D.
,
Martinez
C.
,
Rodriguez
I.
,
Jimenez
F.
(
1991
)
Distribution and function of the lethal of scute gene product during early neurogenesis in Drosophila.
Development
113
,
445
454
Martin-Bermudo
M. D.
,
Gonzalez
F.
,
Dominguez
M.
,
Rodriguez
I.
,
Ruiz-Gomez
M.
,
Romani
S.
,
Modolell
J.
,
Jimenez
F.
(
1993
)
Molecular characterization of the lethal of scute genetic function.
Development
118
,
1003
1012
Martinez
C.
,
Modolell
J.
(
1991
)
Cross-regulatory interactions between the proneural achaete and scute genes of Drosophila.
Science
251
,
1485
1487
Mauhin
V.
,
Lutz
Y.
,
Dennefeld
C.
,
Alberga
A.
(
1993
)
Definition of the DNA-binding site repertoire for the Drosophila transcription factor SNAIL.
Nucl. Acids Res
21
,
3951
3957
Noll
E.
,
Perkins
L. A.
,
Mahowald
A. P.
,
Perrimon
N.
(
1993
)
Approaches to identify genes involved in Drosophila embryonic CNS development.
J. Neurobiol
24
,
701
722
Romani
S.
,
Campuzano
S.
,
Modolell
J.
(
1987
)
The achaetescute complex is expressed in neurogenic regions of Drosophila embryos.
EMBO J
6
,
2085
2092
Ruiz-Gomez
M.
,
Ghysen
A.
(
1993
)
The expression and role of a proneural gene, achaete, in the development of the larval nervous system of Drosophila.
EMBOJ
12
,
1121
1130
Simpson
P.
(
1990
)
Lateral inhibition and the development of the sensory bristles of the adult peripheral nervous system of Drosophila.
Development
109
,
509
519
Skeath
J.
,
Carroll
S.
(
1992
)
Regulation of proneural gene expression and cell fate during neuroblast segregation in the Drosophila embryo.
Development
114
,
939
946
Skeath
J.
,
Panganiban
G.
,
Selegue
J.
,
Carroll
S.
(
1992
)
Gene regulation in two dimensions: the proneural achaete and scute genes are controlled by combinations of axis-patterning genes through a common intergenic control region.
Genes Dev
6
,
2606
2619
Struhl
G.
,
Fitzgerald
K.
,
Greenwald
I.
(
1993
)
Intrinsic activity of the lin-12 and Notch intracellular domains in vivo.
Cell
74
,
331
346
Villares
R.
,
Cabrera
C. V.
(
1987
)
The achaete-scute gene complex of D. melanogaster conserved domains in a subset of genes required for neurogenesis and their homology to myc.
Cell
50
,
415
424
White
K.
(
1980
)
Defective neural development in Drosophila melanogaster embryos deficient for the tip of the X-chromosome.
Dev. Biol
80
,
322
344
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