Neurotrophins signal through members of the trk family of tyrosine kinase receptors and are known to regulate several neuronal properties. Although initially characterized by their ability to prevent naturally occurring cell death of subsets of neurons during development, neurotrophins can also regulate the proliferation and differentiation of precursor cells. Here we report a novel involvement of neurotrophins in early development of the neural tube. We demonstrate that a functional trkB receptor is expressed by motor neuron progenitors in the ventral neural tube and that treatment of ventral neural tube explants with the trkB ligand Brain-Derived Neurotrophic Factor (BDNF) leads to a significant increase in the number of motor neurons. The only BDNF expression detectable at this stage is by a subset of ventrally projecting interneurons in the dorsal neural tube; ablating this region in vivo leads to a reduction of motor neuron numbers. This loss can be prevented by simultaneous treatment with BDNF. We propose that BDNF produced by dorsal interneurons stimulates proliferation and/or differentiation of motor neuron progenitors after anterograde axonal transport and release in proximity to the trkB-expressing motor neuron precursors, thereby coordinating development between dorsal and ventral regions of the neural tube.

REFERENCES

Averbuch-Heller
L.
,
Pruginin
M.
,
Kahane
N.
,
Tsoulfas
P.
,
Parada
L.
,
Rosenthal
A.
,
Kalcheim
C.
(
1994
)
Neurotrophin-3 stimulates the differentiation of motoneurons from avian neural tube progenitor cells.
Proc. Natl. Acad. Sci. USA
91
,
3247
3251
Blochl
A.
,
Thoenen
H.
(
1996
)
Localization of cellular storage compartments and sites of constitutive and activity-dependent release of nerve growth factor (NGF) in primary cultures of hippocampal neurons.
Mol. Cell. Neurosci
7
,
173
190
Bottenstein
J. E.
,
Sato
G. H.
(
1979
)
Growth of a rat neuroblastoma cell line in serum-free supplemented medium.
Proc. Natl. Acad. Sci. USA
76
,
514
517
Chiang
C.
,
Litingtung
Y.
,
Lee
E.
,
Young
K. E.
,
Corden
J. L.
,
Westphal
H.
,
Beachy
P. A.
(
1996
)
Cyclopia and defective axial patterning in mice lacking Sonic hedgehog gene function.
Nature
383
,
407
413
Conover
J. C.
,
Erickson
J. T.
,
Katz
D. M.
,
Bianchi
L. M.
,
Poueymirou
W. T.
,
McClain
J.
,
Pan
L.
,
Helgren
M.
,
Ip
N. Y.
,
Boland
P.
,
Friedman
B.
,
Wiegand
S.
,
Vejsada
R.
,
Kato
A. C.
,
DeChiara
T. M.
,
Yancopoulos
G. D.
(
1995
)
Neuronal deficits, not involving motor neurons, in mice lacking BDNF and/or NT-4.
Nature
375
,
235
238
Covell
D. A.
,
Noden
D. M.
(
1989
)
Embryonic development of the chick primary trigeminal sensory-motor complex.
J. Comp. Neurol
286
,
488
503
Dechant
G.
,
Biffo
S.
,
Okazawa
H.
,
Kohlbeck
R.
,
Pottgiesser
J.
,
Barde
Y.-A.
(
1993
)
Expression and binding characteristics of the BDNF receptor chick trkB.
Development
119
,
545
558
Diaz
C.
,
Glover
J. C.
(
1996
)
Appropriate pattern formation following regulative regneration in the hindbrain neural tube.
Development
122
,
3095
3105
DiCicco-Bloom
E.
,
Friedman
W. J.
,
Black
I. B.
(
1993
)
NT-3 stimulates sympathetic neuroblast proliferation by promoting precursor survival.
Neuron
11
,
1101
1111
Echelard
Y.
,
Epstein
D. J.
,
St.-Jaques
B.
,
Shen
L.
,
Mohler
J.
,
McMahon
J. A.
,
McMahon
A. P.
(
1993
)
Sonic hedgehog, a member of a family of putative signalling molecules, is implicated in the regulation of CNS polarity.
Cell
75
,
1417
1430
ElShamy
W. M.
,
Ernfors
P.
(
1996
)
A local action of neurotrophin-3 prevents the death of proliferating sensory neuron precursor cells.
Neuron
16
,
963
972
ElShamy
W. M.
,
Linnarsson
S.
,
Lee
K.-F.
,
Jaenisch
R.
,
Ernfors
P.
(
1996
)
Prenatal and postnatal requirements of NT-3 for symapthetic neuroblast survival and innernvation of specific targets.
Development
122
,
491
500
Ericson
J.
,
Thor
S.
,
Edlund
T.
,
Jessell
T. M.
,
Yamada
T.
(
1992
)
Early stages of motor neuron differentiation revealed by expression of homeobox gene islet-1.
Science
256
,
1555
1560
Ericson
J.
,
Morton
S.
,
Kawakami
A.
,
Roelink
H.
,
Jessell
T. M.
(
1996
)
Two critical periods of sonic hedgehog signaling required for the specification of motor neuron identity.
Cell
87
,
661
673
Ernfors
P.
,
Lee
K.-F.
,
Jaenisch
R.
(
1994
)
Mice lacking brain-derived neurotrophic factor develop with sensory deficits.
Nature
368
,
147
150
Gaese
F.
,
Kolbeck
R.
,
Barde
Y.-A.
(
1994
)
Sensory ganglia require neurotrophin-3 early in development.
Development
120
,
1613
1619
Gavrieli
Y.
,
Sherman
Y.
,
Ben-Sasson
S. A.
(
1992
)
Identification of programmed cell death in situ via specific labeling of nuclear DNA fragmentation.
J. Cell Biology
119
,
493
501
Goulding
M.
,
Lumsden
A.
,
Gruss
P.
(
1993
)
Signals from the notochord and floor plate regulate the region-specific expression of two Pax genes in the developing spinal cord.
Development
117
,
1001
1016
Hamburger
V.
,
Hamilton
H.
(
1951
)
A series of normal stages in the development of the chick embryo.
J. Morphol
88
,
49
92
Heaton
M. B.
,
Moody
S. A.
(
1980
)
Early development and migration of the trigeminal motor nucleus in the chick embryo.
J. Comp. Neurol
189
,
61
99
Herzog
K.-H.
,
Bailey
K.
,
Barde
Y.-A.
(
1994
)
Expression of the BDNF gene in the developing visual system of the chick.
Development
120
,
1643
1649
Heyman
I.
,
Faissner
A.
,
Lumsden
A.
(
1995
)
Cell and matrix specialisations of rhombomere boundaries.
Dev. Dyn
204
,
301
315
Holley
J. A.
(
1982
)
Early development of the circumferential axonal pathway in mouse and chick spinal cord.
J. Comp. Neurol
205
,
371
382
Hollyday
M.
,
Hamburger
V.
(
1977
)
An autoradiographic study of the formation of the lateral motor column in the chick embryo.
Brain Res
132
,
197
208
Homma
S.
,
Yaginuma
H.
,
Oppenheim
R. W.
(
1994
)
Programmed cell death during the earliest stages of spinal cord development in the chick embryo: a possible means of early phenotypic selection.
J. Comp. Neurol
345
,
377
395
Jones
K. R.
,
Farinas
I.
,
Backus
C.
,
Reichardt
L. F.
(
1994
)
Targeted disruption of the brain-derived neurotrophic factor gene perturbs brain and sensory neuron but not motor neuron development.
Cell
76
,
989
1000
Kahane
N.
,
Shelton
D. L.
,
Kalcheim
C.
(
1996
)
Expression and regulation of brain-derived neurotrophic factor and neurotrophin-3 mRNAs in distinct avian motoneuron subsets.
J. Neurobiol
29
,
277
292
Kalcheim
C.
,
Carmeli
C.
,
Rosenthal
A.
(
1992
)
Neurotrophin-3 is a mitogen for cultured neural crest cells.
Proc. Natl. Acad. Sci. USA
89
,
1661
1665
Karlsson
O.
,
Thor
S.
,
Norbert
T.
,
Ohlsson
H.
,
Edlund
T.
(
1990
)
Insulin gene enhancer binding protein Isl-1 is a member of a novel class of proteins containing both a homeo and a Cys-His domain.
Nature
344
,
879
882
Klein
R.
,
Smeyne
R. J.
,
Wurst
W.
,
Long
L. K.
,
Auerbach
B. A.
,
Joyner
A. L.
,
Barbacid
M.
(
1993
)
Targeted disruption of the trkB neurotrophin receptor gene results in nervous system lesions and neonatal death.
Cell
75
,
113
122
Leber
S. M.
,
Sanes
J. R.
(
1995
)
Migratory paths of neurons and glia in the embryonic chick spinal cord.
J. Neurosci
15
,
1236
1248
Leibrock
J.
,
Lottspeich
F.
,
Hohn
A.
,
Hofer
M.
,
Hengerer
B.
,
Masiakowski
P.
,
Thoenen
H.
,
Barde
Y.-A.
(
1989
)
Molecular cloning and expression of brain-derived neurotrophic factor.
Nature
341
,
149
152
Liem
K. F.
,
Tremml
G.
,
Roelink
H.
,
Jessell
T. J.
(
1995
)
Dorsal differentiation of neural plate cells induced by BMP-mediated signals from epidermal ectoderm.
Cell
82
,
969
979
Liu
X.
,
Ernfors
P.
,
Wu
H.
,
Jaenisch
R.
(
1995
)
Sensory but not motor neuron deficits in mice lacking NT-4 and BDNF.
Nature
375
,
238
241
Marti
E.
,
Bumcrot
D. A.
,
Takada
R.
,
McMahon
A. P.
(
1995
)
Requirement of 19K form of sonic hedgehog for induction of distinct ventral cell types in CNS explants.
Nature
375
,
322
325
McConnell
S. K.
,
Kaznowski
C. E.
(
1991
)
Cell cycle dependence of laminar determination in developing cerebral cortex.
Science
254
,
282
285
McKay
S. E.
,
Garner
A.
,
Caldero
J.
,
Tucker
R. P.
,
Large
T.
,
Oppenheim
R. W.
(
1996
)
The expression of trkB and the role of BDNF in the developing neuromuscular system of the chick embryo.
Development
122
,
715
724
Heaton
M. B.
,
Moody
S. A.
(
1980
)
Early development and migration of the trigeminal motor nucleus in the chick embryo.
J. Comp. Neurol
189
,
61
99
Ockel
M.
,
Lewin
G. R.
,
Barde
Y.-A.
(
1996
)
In vivo effects of neurotrophin-3 during sensory neurogenesis.
Development
122
,
301
307
Oppenheim
(
1991
)
Cell death during development of the nervous system.
Ann. Rev. Neurosci
14
,
453
501
Pfaff
S. L.
,
Mendelsohn
M.
,
Stewart
C. L.
,
Edlund
T.
,
Jessell
T. M.
(
1996
)
Requirement for LIM homeobox gene isl-1 in motor neuron generation reveals a motor neuron-dependent step in interneuron differentiation.
Cell
84
,
309
320
Roelink
H.
,
Augsberger
A.
,
Heemskerk
J.
,
Korzh
V.
,
Norlin
S.
,
Ruiz y Altaba
A.
,
Tanabe
Y.
,
Placzek
M.
,
Edlund
T.
,
Jessell
T. M.
,
Dodd
J.
(
1994
)
Floor plate and motor neuron induction by vhh-1, a vertebrate homologue of hedgehog expressed by the notochord.
Cell
76
,
761
755
Roelink
H.
,
Porter
J. A.
,
Chiang
C.
,
Tanabe
Y.
,
Chang
D. T.
,
Beachy
P. A.
,
Jessell
T. M.
(
1995
)
Floor plate and motor neuron induction by different concentrations of the amino-terminal cleavage product of sonic hedgehog autoproteolysis.
Cell
81
,
445
455
Shiga
T.
,
Oppenheim
R. W.
(
1991
)
Immunolocalization studies of putative guidance molecules used by axons and growth cones of intersegmental interneurons in the chick embryo spinal cord.
J. Comp. Neurol
310
,
234
252
Sieber-Blum
M.
(
1991
)
Role of the neurotrophic factors BDNF and NGF in the commitment of pluripotent neural crest cells.
Neuron
6
,
949
955
Simon
H.
,
Guthrie
S.
,
Lumsden
A.
(
1994
)
Regulation of SC1/DM-GRASP during the migration of motor neurons in the chick embryo brain stem.
J. Neurobiol
25
,
1129
1143
Snider
W. D.
(
1994
)
Functions of the neurotrophins during nervous system development: what the knockouts are teaching us.
Cell
77
,
627
638
Tanabe
Y.
,
Jessell
T. M.
(
1996
)
Diversity and pattern in the developing spinal cord.
Science
274
,
1115
1123
Thoenen
H.
(
1995
)
Neurotrophins and neuronal plasticity.
Science
270
,
593
598
Tsuchida
T.
,
Ensini
M.
,
Morton
S. B.
,
Baldassare
M.
,
Edlund
T.
,
Jessell
T. M.
,
Pfaff
S. L.
(
1994
)
Topographic organization of embryonic motor neurons defined by expression of LIM homeobox genes.
Cell
79
,
957
970
Van Straaten
H. M. W.
,
Hekking
J. M. W.
,
Wiertz-Hoessels
E. L.
,
Thors
F.
,
Drukker
J.
(
1988
)
Effect of the notochord on the differentiation of a floor plate area in the neural tube of the chick embryo.
Anat. Embryol
177
,
317
324
Van Straaten
H. M. W.
,
Hekking
J. W. M.
(
1991
)
Development of floor plate, neurons and axonal outgrowth pattern in the early spinal cord ot the notochord-deficient chick embryo.
Anat. Embryol
184
,
55
63
Von Bartheld
C. S.
,
Byers
M. R.
,
Williams
R.
,
Bothwell
M.
(
1996
)
Anterograde transport of neurotrophins and axodendritic transfer in the developing visual system.
Nature
379
,
830
833
Wentworth
L. E.
(
1984
)
The development of the cervical spinal cord of the mouse embryo. II. A golgi analysis of sensory, commissural and association cell differentiation.
J. Comp. Neurol
222
,
96
115
Xu
Y.
,
Baldassare
M.
,
Fisher
P.
,
Rathbun
G.
,
Oltz
E. M.
,
Yancopoulos
G. D.
,
Jessell
T. M.
,
Alt
F. W.
(
1993
)
LH-2: a LIM/homeodomain gene expressed in developing lymphocytes and neural cells.
Proc. Natl. Acad. Sci. USA
90
,
227
231
Yaginuma
H.
,
Shiga
T.
,
Homma
S.
,
Ishihara
R.
,
Oppenheim
R. W.
(
1990
)
Identification of early developing axon projections from spinal interneurons in the chick embryo with a neuron-specific beta-tubulin antibody: evidence for a new pioneer pathway in the spinal cord.
Development
108
,
705
716
Yamada
T.
,
Placzek
M.
,
Tanaka
H.
,
Dodd
J.
,
Jessell
T. M.
(
1991
)
Control of cell pattern in the developing nervous system: polarizing activity of the floor plate and notochord.
Cell
64
,
635
647
This content is only available via PDF.