The central nervous system (CNS) represents an excellent model system for examining how a multitude of unique cell fates are specified. We find that asymmetric localization of the numb protein autonomously controls a binary cell fate decision in the Drosophila CNS. The simplest lineage in the Drosophila CNS is that of the MP2 precursor: it divides unequally to generate the dMP2 and vMP2 neurons. Both are interneurons but project in different directions: dMP2 projects its axon posteriorly while vMP2 projects anteriorly. During MP2 mitosis, numb is localized into dMP2 and excluded from vMP2. Loss of numb transforms dMP2 into vMP2, whereas ectopic numb produces the opposite transformation of vMP2 into dMP2. Thus, numb is asymmetrically localized in the dividing MP2 and is necessary and sufficient to autonomously specify dMP2 neuronal identity.

Reference

Campbell
G.
,
Goring
H.
,
Lin
T.
,
Spana
E.
,
Anderson
S.
,
Doe
C. Q.
,
Tomlinson
A.
(
1994
)
RK2, a glial-specific homeodomain protein is required for embyonic nerve cord condensation and viability in Drosophila.
Development
120
,
2957
2966
Chu-LaGraff
Q.
,
Doe
C. Q.
(
1993
)
Neuroblast specification and formation regulated by wingless in the Drosophila CNS.
Science
261
,
1594
1597
Doe
C. Q.
(
1992
)
Molecular markers for identified neuroblasts and ganglion mother cells in the Drosophila central nervous system.
Development
116
,
855
863
Frasch
M.
,
Hoey
T.
,
Rushlow
C.
,
Doyle
H.
,
Levine
M.
(
1986
)
Characterisation and localisation of the even-skipped protein of Drosophila.
EMBO J
6
,
749
759
Fujita
S. C.
,
Zipursky
S. L.
,
Benzer
S.
,
Ferrus
A.
,
Shotwell
S. L.
(
1982
)
Monoclonal antibodies against the Drosophila nervous system.
Proc. Natl. Acad. Sci. USA
79
,
7929
7933
Greenwald
I.
,
Rubin
G. M.
(
1992
)
Making a difference: The role of cell-cell interactions in establishing separate identities for equivalent cells.
Cell
68
,
271
281
Hartenstein
V.
,
Posakony
J. W.
(
1990
)
A dual function of the Notch gene in Drosophila sensillum development.
Dev. Biol
142
,
13
30
Horvitz
H. R.
,
Herskowitz
I.
(
1992
)
Mechanisms of asymmetric cell division: Two Bs or not two Bs, that is the question.
Cell
68
,
237
255
Huff
R.
,
Furst
A.
,
Mahowald
A. P.
(
1989
)
Drosophila embryonic neuroblasts in culture: autonomous differentiation of specific neurotransmitters.
Dev. Biol
134
,
146
157
Jan
Y. N.
,
Jan
L. Y.
(
1995
)
Maggot's hair and bug's eye: Role of cell interactions and intrinsic factors in cell fate specification.
Neuron
14
,
1
5
Kuwada
J. Y.
,
Goodman
C. S.
(
1985
)
Neuronal determination during embryonic development of the grasshopper nervous system.
Dev. Biol
110
,
114
126
Lin
D. M.
,
Fetter
R. D.
,
Kopczynski
C.
,
Grenningloh
G.
,
Goodman
C. S.
(
1994
)
Genetic analysis of fasciclin II in Drosophila: defasciculation, refasciculation and altered fasciculation.
Neuron
13
,
1055
1069
Lundell
M. J.
,
Hirsh
J.
(
1994
)
A new visible light DNA fluorochrome for confocal microscopy.
BioTechniques
16
,
434
440
Menne
T. V.
,
Klambt
C.
(
1994
)
The formation of commisures in the Drosophila CNS depends on the midline cells and on the Notch gene.
Dev. Biol
120
,
123
133
Parks
A. L.
,
Muskavitch
M. A. T.
(
1993
)
Delta function is required for bristle organ determination and morphogenesis in Drosophila.
Dev. Biol
157
,
484
496
Posakony
J. W.
(
1994
)
Nature versus nurture: Asymmetric cell divisions in Drosophila bristle development.
Cell
76
,
415
418
Rhyu
M. S.
,
Jan
L. Y.
,
Jan
Y. N.
(
1994
)
Asymmetric distribution of numb protein during division of the sensory organ precursor cell confers distinct fates to daughter cells.
Cell
76
,
477
491
Spana
E. P.
,
Doe
C. Q.
(
1995
)
The prospero transcription factor is asymmetrically localized to the cell cortex during neuroblast mitosis in Drosophila.
Development
121
,
3489
3494
Tepass
U.
,
Knust
E.
(
1993
)
crumbs and stardust act in a genetic pathway that controls the organization of epithelia in Drosophila melanogaster.
Dev. Biol
159
,
311
326
Udolph
G.
,
Prokop
A.
,
Bossing
T.
,
Technau
G. M.
(
1993
)
A common precursor for glia and neurons in the embryonic CNS of Drosophila gives rise to segment-specific lineage variants.
Development
118
,
765
775
Uemura
T.
,
Shepherd
S.
,
Ackerman
L.
,
Jan
L. Y.
,
Jan
Y. N.
(
1989
)
numb, a gene required in determination of cell fate during sensory organ formation in Drosophila embyros.
Cell
58
,
349
360
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