The POU homeobox gene unc-86 specifies many neuroblast and neural fates in the developing C. elegans nervous system. Genes regulated by unc-86 are mostly unknown. Here we describe a genetic strategy for the identification of downstream pathways regulated by unc-86. We activate UNC-86 transcription activity by inserting the VP16 activation domain into an unc-86 genomic clone that bears all regulatory sequences necessary for normal expression in C. elegans. unc-86/VP16 complements unc-86 mutations in the specification of neuroblast and neural cell fates, but displays novel genetic activities: it can suppress non-null mutations in the downstream genes mec-3 and mec-7 that are necessary for mechanosensory neuron differentiation and function. These data suggest that UNC-86/VP16 increases the expression of mec-3 and mec-7 to compensate for the decreased activities of mutant MEC-3 or MEC-7 proteins. The suppression of mutations in downstream genes by an activated upstream transcription factor should be a general strategy for the identification of genes in transcriptional cascades. unc-86/VP16 also causes neural migration and pathfinding defects and novel behavioral defects. Thus, increased or unregulated expression of genes downstream of unc-86 can confer novel neural phenotypes suggestive of roles for unc-86-regulated genes in neural pathfinding and function. Genetic suppression of these unc-86/VP16 phenotypes may identify the unc-86 downstream genes that mediate these events in neurogenesis.

Aigner
L.
,
Arbert
S.
,
Kapfhammer
J. P.
,
Laux
T.
,
Schneider
C.
,
Botteri
F.
,
Brenner
H.-R.
,
Caroni
P.
(
1995
)
Overexpression of the neural growth-associated protein GAP-43 induces nerve sprouting in the adult nervous system of transgenic mice.
Cell
83
,
269
278
Aoyama
T.
,
Dong
C. H.
,
Wu
Y.
,
Carabelli
M.
,
Sessa
G.
,
Ruberti
I.
,
Morelli
G.
,
Chua
N. H.
(
1995
)
Ectopic expression of the Arabidopsis transcriptional activator Athb-1 alters leaf cell fate in tobacco.
Plant Cell
7
,
1773
1785
Basson
M.
,
Horvitz
H. R.
(
1996
)
The C. elegans gene sem-4 controls neuronal and mesodermal cell development and encodes a zinc-finger protein.
Genes Dev
10
,
1953
1965
Baumeister
R.
,
Liu
Y. X.
,
Ruvkun
G.
(
1996
)
Lineage-specific regulators couple cell lineage asymmetry to the transcription of the Caenorhabditis elegans POU gene unc-86 during neurogenesis.
Genes Dev
10
,
1395
1410
Bourtchuladze
R.
,
Frenguelli
B.
,
Blendy
J.
,
Cioffi
D.
,
Schutz
G.
,
Silva
A. J.
(
1994
)
Deficient long-term memory in mice with a targeted mutation of the cAMP-responsive element-binding protein.
Cell
79
,
59
68
Brenner
S.
(
1974
)
The genetics of Caenorhabditis elegans.
Genetics
77
,
71
94
Chalfie
M.
,
Horvitz
H. R.
,
Sulston
J. E.
(
1981
)
Mutations that lead to reiterations in the cell lineages of C. elegans.
Cell
24
,
59
69
Chalfie
M.
,
Sulston
J.
(
1981
)
Developmental genetics of the mechanosensory neurons of Caenorhabditis elegans.
Dev. Biol
82
,
358
370
Chalfie
M.
,
Sulston
J. E.
,
White
J. G.
,
Southgate
E.
,
Thomson
J. N.
,
Brenner
S.
(
1985
)
The neural circuit for touch sensitivity in Caenorhabditis elegans.
J. Neurosci
5
,
956
964
Chalfie
M.
,
Tu
Y.
,
Euskirchen
G.
,
Ward
W. W.
,
Prasher
D. C.
(
1994
)
Green fluorescent protein as a marker for gene expression.
Science
263
,
802
805
Culotti
J. G.
(
1994
)
Axon guidance mechanisms in Caenorhabditis elegans.
Curr. Opin. Genet. Dev
4
,
587
595
Desai
C.
,
Garriga
G.
,
McIntire
S. L.
,
Horvitz
H. R.
(
1988
)
A genetic pathway for the development of the Caenorhabditis elegans HSN motor neurons.
Nature
336
,
638
646
Desai
C.
,
Horvitz
H. R.
(
1989
)
Caenorhabditis elegans mutants defective in the functioning of the motor neurons responsible for egg laying.
Genetics
121
,
703
721
Erkman
L.
,
McEvilly
R. J.
,
Luo
L.
,
Ryan
A. K.
,
Hooshmand
F.
,
O'Connell
S. M.
,
Keithley
E. M.
,
Rapaport
D. H.
,
Ryan
A. F.
,
Rosenfeld
M. G.
(
1996
)
Role of transcription factors Brn-3. 1 and Brn-3. 2 in auditory and visual system development.
Science
381
,
603
606
Finney
M.
,
Ruvkun
G.
,
Horvitz
H. R.
(
1988
)
The C. elegans cell lineage and differentiation gene unc-86 encodes a protein with a homeodomain and extended similarity to transcription factors.
Cell
55
,
757
769
Finney
M.
,
Ruvkun
G.
(
1990
)
The unc-86 gene product couples cell lineage and cell identity in C. elegans.
Cell
63
,
895
905
Gaul
U.
,
Change
H.
,
Choi
T.
,
Karim
F.
,
Rubin.
G. M.
(
1993
)
Identification of ras targets using a genetic approach.
Ciba Found. Symp
176
,
85
92
Goodman
C. S.
,
Shatz
C. J.
(
1993
)
Developmental mechanisms that generate precise patterns of neuronal connectivity.
Cell
72
,
77
98
Goodrich
J. A.
,
Hoey
T.
,
Thut
C. J.
,
Admon
A.
,
Tjian
R.
(
1993
)
Drosophila TAFII40 interacts with both a VP16 activation domain and the basal transcription factor TFIIB.
Cell
75
,
519
30
Hamelin
M.
,
Scott
I.
,
Way
J.
,
Culotti
J.
(
1992
)
The mec-7-tubulin gene of Caenorhabditis elegans is expressed primarily in the touch receptor neurons.
EMBO J
11
,
2885
2893
Hamelin
M.
,
Zhou
Y.
,
Su
M.
,
Scott
I. M.
,
Culotti
J. G.
(
1993
)
Expression of the UNC-5 guidance receptor in the touch neurons of C. elegans steers their axons dorsally.
Nature
364
,
327
330
Hart
A. C.
,
Sims
S.
,
Kaplan
J. M.
(
1995
)
Synaptic code for sensory modalities revealed by C. elegans GLR-1 glutamate receptor.
Nature
378
,
82
85
Hedgecock
E. M.
,
Culotti
J. G.
,
Hall
D. H.
(
1990
)
The unc-5, unc-6, and unc-40 genes guide circumferential migrations of pioneer axons and mesodermal cells on the epidermis in C. elegans.
Neuron
4
,
61
85
Hynes
R. O.
,
Lander
A. D.
(
1992
)
Contact and adhesive specificities in the associations, migrations, and targeting of cells and axons.
Cell
68
,
303
322
Ishii
N.
,
Wadsworth
W. G.
,
Stern
B. D.
,
Culotti
J. G.
,
Hedgecock
E. M.
(
1992
)
UNC-6, a laminin-related protein, guides cell and pioneer axon migrations in C. elegans.
Neuron
9
,
873
881
Jarman
A. P.
,
Brand
M.
,
Jan
L. Y.
,
Jan
Y. N.
(
1993
)
The regulation and function of the helix-loop-helix gene, asense, in Drosophila neural precursors.
Development
119
,
19
29
Jin
Y.
,
Hoskins
R.
,
Horvitz
H. R.
(
1994
)
Control of type-D GABAergicneuron differentiation by C. elegans UNC-30 homeodomain protein.
Nature
372
,
780
783
Johnson
W. A.
,
Hirsh
J.
(
1990
)
Binding of a Drosophila POU-domain protein to a sequence element regulating gene expression in specific dopaminergic neurons.
Nature
343
,
467
470
Kalderon
D.
,
Roberts
B. L.
,
Richardson
W. D.
,
Smith
A. E.
(
1984
)
A short amino acid sequence able to specify nuclear location.
Cell
39
,
499
509
Klemm
J. D.
,
Rould
M. A.
,
Aurora
R.
,
Herr
W.
,
Pabo
C. O.
(
1994
)
Crystal structure of the Oct-1 POU domain bound to an octamer site: DNA recognition with tethered DNA-binding modules.
Cell
77
,
21
32
Kolodkin
A. L.
,
Matthes
D. J.
,
O'Connor
T. P.
,
Patel
N. H.
,
Admon
A.
,
Bentley
D.
,
Goodman
C. S.
(
1992
)
Fasciclin IV: sequence, expression, and function during growth cone guidance in the grasshopper embryo.
Neuron
9
,
831
845
Lackner
M. R.
,
Kornfeld
K.
,
Miller
L. M.
,
Horvitz
H. R.
,
Kim
S. K.
(
1994
)
A MAP kinase homolog, mpk-1, is involved in ras-mediated induction of vulval cell fates in Caenorhabditis elegans.
Genes Dev
8
,
160
173
Lakin
N. D.
,
Morris
P. J.
,
Theil
T.
,
Sato
T. N.
,
Möröy
T.
,
Wilson
M. C.
,
Latchman
D. S.
(
1995
)
Regulation of neurite outgrowth and SNAP-25 gene expression by the Brn-3a transcription factor.
J. Biol. Chem
270
,
15858
15863
Lewin
B.
(
1994
)
On neuronal specificity and the molecular basis of perception.
Cell
79
,
935
943
Lichtsteiner
S.
,
Tjian
R.
(
1995
)
Synergistic activation of transcription by UNC-86 and MEC-3 in Caenorhabditis elegans embryo extracts.
EMBO J
14
,
3937
3945
Lundgren
S. E.
,
Callahan
C. A.
,
Thor
S.
,
Thomas
J. B.
(
1995
)
Control of neuronal pathway selection by the Drosophila LIM homeodomain gene apterous.
Development
121
,
1769
1773
Maricq
A. V.
,
Peckol
E.
,
Driscoll
M.
,
Bargmann
C. I.
(
1995
)
Mechanosensory signaling in C. elegans mediated by the GLR-1 glutamate receptor.
Nature
378
,
78
81
McIntire
S. L.
,
Jorgensen
E.
,
Horvitz
H. R.
(
1993
)
Genes required for GABA function in Caenorhabditis elegans.
Nature
364
,
334
347
Meier
T.
,
Therianos
S.
,
Zacharias
D.
,
Reichert
H.
(
1993
)
Developmental expression of TERM-1 glycoprotein on growth cones and terminal arbors of individual identified neurons in the grasshopper.
J Neurosci
13
,
1498
1510
Mello
C. C.
,
Kramer
J. M.
,
Stinchcomb
D.
,
Ambros
V.
(
1991
)
Efficient gene transfer in C. elegans: extrachromosomal maintenance and integration of transforming sequences.
EMBO J
10
,
3959
3970
Mendel
J. E.
,
Korswagen
H. D.
,
Liu
K. S.
,
Hajdu-Cronin
Y. M.
,
Simon
M. I.
,
Plasterk
R. H.
,
Sternberg
P. W.
(
1995
)
Participation of the protein Go in multiple aspects of behavior in C. elegans.
Science
267
,
1652
1655
Miller
D. M.
,
Shen
M. M.
,
Shamu
C. E.
,
Burglin
T. R.
,
Ruvkun
G.
,
Dubois
M. L.
,
Ghee
M.
,
Wilson
L.
(
1992
)
C. elegansunc-4 gene encodes a homeodomain protein that determines the pattern of synaptic imput to specific motor neurons.
Nature
355
,
841
845
Mitani
S.
,
Du
H.
,
Hall
D. H.
,
Driscoll
M.
,
Chalfie
M.
(
1993
)
Combinatiorial control of touch receptor neuron expression in Caenorhabditis elegans.
Development
119
,
773
783
Mori
I.
,
Ohshima
Y.
(
1995
)
Neural regulation of thermotaxis in Caenorhabditis elegans.
Nature
376
,
344
348
Nevins
J. R.
(
1991
)
Transcriptional activation by viral regulatory proteins.
Trends Biochem. Sci
16
,
435
439
Rankin
C. H.
,
Beck
C. D. O.
,
Chiba
C. M.
(
1990
)
C. elegans, a newmodel system for the study of learning and memory.
Behav. Brain Res
37
,
899
892
Sadowski
I.
,
Ma
J.
,
Triezenberg
S.
,
Ptashne
M.
(
1988
)
GAL4-VP16 is an unusually potent transcriptional activator.
Nature
335
,
563
564
Salser
S. J.
,
Loer
C. M.
,
Kenyon
C.
(
1993
)
Multiple HOM-C gene interactions specify cell fates in the nematode central nervous system.
Genes Dev
7
,
1714
1724
Savage
C.
,
Xue
Y.
,
Mitani
S.
,
Hall
D.
,
Zakhary
R.
,
Chalfie
M.
(
1994
)
Mutations in the Caenorhabditis elegans -tubulin gene mec-7: effects on microtubule assembly and stability and on tubulin autoregulation.
J. Cell Sci
107
,
2165
2175
Schier
A. F.
,
Gehring
W. J.
(
1992
)
Direct homeodomain-DNA interaction in the regulation of the fushi tarazu gene.
Nature
356
,
804
807
Sengupta
P.
,
Colbert
H. A.
,
Bargmann
C. I.
(
1994
)
The C. elegans gene odr-7 encodes an olfactory-specific member of the nuclear receptor superfamily.
Cell
79
,
971
980
Skene
J. H. P.
(
1989
)
Axonal growth-associated proteins.
Annu. Rev. Neurosci
12
,
127
156
Tanaka
M.
,
Herr
W.
(
1990
)
Differential transcriptional activation by Oct-1 and Oct-2: interdependent activation domains induce Oct-2 phosphorylation.
Cell
60
,
375
386
Triezenberg
S. J.
,
Kingsbury
R.
,
McKnight
S. L.
(
1988
)
Functional dissection of VP16, the transactivator of herpes simplex virus immediate early gene expression.
Genes Dev
2
,
718
729
Way
J.
,
Chalfie
M.
(
1988
)
mec-3, a homeobox-containing gene that specifies differentiation of the touch receptor neurons in C. elegans.
Cell
54
,
5
16
Way
J.
,
Chalfie
M.
(
1989
)
The mec-3 gene of Caenorhabditis elegans requires its own products for maintained expression and is expressed in three neuronal cell types.
Genes Dev
3
,
1823
1833
White
J. G.
,
Southgate
E.
,
Thomson
J. N.
,
Brenner
S.
(
1986
)
The structure of the nervous system of the nematode Caenorhabditis elegans.
Phil. Trans. R. Soc. Lond
314
,
1
340
Wu
Y.
,
Han
M.
(
1994
)
Suppression of activated LET-60 ras protein defines a role of Caenorhabditis elegansSur-1 MAP kinase in vulval differentiation.
Genes Dev
8
,
147
159
Xiao
H.
,
Friesen
J. D.
,
Lis
J. T.
(
1994
)
A highly conserved domain of RNA polymerase II shares a functional element with acidic activation domains of upstream transcription factors.
Mol. Cell Biol
14
,
7507
7516
Xue
D.
,
Finney
M.
,
Ruvkun
G.
,
Chalfie
M.
(
1992
)
Regulation of the mec-3 gene by the C. elegans homeoproteins UNC-86 and MEC-3.
EMBO J
11
,
4969
4979
Xue
D.
,
Tu
Y.
,
Chalfie
M.
(
1993
)
Cooperative interactions between the Caenorhabditis elegans homeoproteins unc-86 and mec-3.
Science
261
,
1324
1328
Yin
J. C. P.
,
Del Vecchio
M.
,
Zhou
H.
,
Tully
T.
(
1995
)
CREB as a memory modulator: induced expression of a dCREB2 activator isoform enhances long-term memory in Drosophila.
Cell
81
,
107
115
This content is only available via PDF.