1 Department Preclinical Veterinary Sciences, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall Square, Edinburgh EH9 1QH, UK
Author for correspondence (e-mail:
humberto.g{at}ed.ac.uk)
Accepted 7 April 2004
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SUMMARY |
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Key words: MET, c-MET, Neurons, Process growth, GFP, Slice cultures
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Introduction |
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HGF plays a role in several aspects of neural development
(Maina and Klein, 1999).
Experiments in chick embryos have suggested that HGF might play a role in
neural induction (Bonner-Fraser,
1995
). Later in embryonic development and in the adult nervous
system a variety of neurons and glial cells express HGF and MET
(Andermarcher et al., 1996
;
Di Renzo et al., 1993
;
Jung et al., 1994
;
Krasnoselsky et al., 1994
;
Maina et al., 1997
;
Sonnenberg et al., 1993
;
Thewke and Seeds, 1999
). HGF
promotes the survival of a subset of motoneurons and has been implicated in
guiding a subset of motor axons to their targets
(Ebens et al., 1996
;
Wong et al., 1997
;
Yamamoto et al., 1997
). HGF
promotes the survival of sympathetic neuroblasts
(Maina et al., 1998
) and
enhances the survival of subsets of parasympathetic and sensory neurons grown
with ciliary neurotrophic factor (CNTF) and nerve growth factor (NGF),
respectively (Davey et al.,
2000
; Maina et al.,
1997
; Yang et al.,
1998
). HGF also enhances neurite growth from these neurons
cultured with neurotrophic factors, and mice possessing a non-functional MET
receptor have shorter, less branched spinal sensory nerves in vivo than
wild-type embryos (Maina et al.,
1997
). HGF also increases the number of calbindin D-expressing
neurons in postnatal rat hippocampal cultures and increases neurite outgrowth
from these neurons (Korhonen et al.,
2000
).
HGF and MET are widely expressed in the developing and mature mouse brain,
with expression beginning as early as embryonic day 12 (E12) and E13,
respectively (Achim et al.,
1997; Jung et al.,
1994
; Thewke and Seeds,
1999
). In the cerebral cortex, HGF is expressed in pyramidal
neurons of layers IV and V, whereas MET is expressed in cortical neurons of
layers II, III, IV and V. Other sites of HGF expression include the
hippocampus, granule cell layer of the cerebellum, ependymal cells, chorioid
plexus, and pineal body (Jung et al.,
1994
; Korhonen et al.,
2000
). MET is also expressed in the CA-1 area of the hippocampus,
the septum and the pons (Thewke and Seeds,
1999
).
Despite the extensive expression of HGF and MET in the central nervous
system (CNS), only a handful of studies have begun to investigate the
potential functions of MET signaling in the brain. HGF enhances the survival
of tyrosine hydroxylase-positive midbrain neurons
(Hamanoue et al., 1996) and
hippocampal neurons (Honda et al.,
1995
) in culture. In vivo, HGF rescues hippocampal CA1 neurons
following transient global ischemia
(Miyazawa et al., 1998
) and
rescues cerebellar granule neurons following N-methyl-D-aspartate (NMDA) and
quinolinic acid-induced excitotoxicity
(Zhang et al., 2000
). HGF also
promotes the migration of cortical interneurons from the ventral to the dorsal
telencephalon in rodents (Powell et al.,
2001
), and MET signaling has been implicated in regulating the
proliferation and differentiation of cerebellar granule cells
(Ieraci et al., 2002
).
To assess the possible role of HGF in regulating the morphology of CNS
neurons, we examined the effect of exogenous HGF and blockade of endogenous
HGF on the growth of postnatal cortical pyramidal dendrites in organotypic
slice cultures of mouse somatosensory cortex. These cultures have the
advantage of preserving the local three-dimensional environment of each
neuron, the laminar organization of the cortex and the pattern of connections
within and between these layers (Hayar et
al., 1999; McAllister et al.,
1995
). Using particle-mediated gene transfer, a subset of
pyramidal neurons were labeled with GFP and their morphology was examined by
confocal microscopy. These studies revealed that manipulating the supply of
HGF in these cultures markedly affects the dendritic arbors of layer 2
pyramidal neurons: HGF increasing, and anti-HGF decreasing, dendritic growth.
These results demonstrate that HGF and MET signaling in the cortex stimulates
dendritic growth and may play a role in regulating neuronal plasticity in the
developing cerebral cortex.
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Materials and methods |
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Gene transfer
The dendritic arbors of cortical pyramidal neurons were visualized by
transfecting these neurons with an enhanced green fluorescent protein (EGFP)
expression plasmid (Clontech) using the hand-held gene-gun (Helios Gene-gun,
BioRad) 1 hour after slice preparation. Gold particle cartridges were prepared
beforehand using the manufacturer's protocol. Briefly, 20 mg of 1.6 µm gold
particles were suspended in 100 µl of 50 mM spermidine and 20 µg of
plasmid DNA (pEGFP, Clontech). The gold particles were then precipitated with
100 µl of 2M CaCl2, washed three times with 100% ethanol,
resuspended in 1.2 ml of 100% ethanol plus 0.01mg/ml poliviniylpirrolidone and
loaded into Teflon tubing microcarriers. The gold particles in the
microcarriers were shot into the slices at a pressure of 250-300 psi. A 70
µm nylon mesh screen was placed between the gun and the slice to protect
the tissue from the shock wave. For MET kinase-dead transfections, cartridges
were prepared by co-precipitating 20 µg of the pEGFP plasmid and 20 µg
of the MET KD expression vector (kindly provided by Flavio Maina, Marseilles).
Control transfections were carried out with cartridges carrying pEGFP and the
corresponding empty vector.
Reagents
Recombinant human HGF (R&D) and BDNF (Genentech) were used at a
concentration of 200 ng/ml, and function-blocking anti-HGF (polyclonal
anti-human HGF antibody R&D) was used at concentrations of 1 and 3
µg/ml. In some experiments, HGF was pre-incubated with anti-HGF for 1 hour
at 37°C before adding to the cultures. Reagents were added immediately
after bombardment.
Dendritic analysis
Forty-eight hours after transfection, layer 2 pyramidal neurons of the
somatosensory cortex were studied with an Axioplan Zeiss laser scanning
confocal microscope. Thirty minutes fixation with 4% paraformaldehyde in PBS
and DAPI counterstaining was used to confirm the laminar localization. For
every experimental condition studied, the dendritic organization of between 50
and 60 neurons was reconstructed and analysed. GFP-expressing cells were
selected for analysis only if they where in layer 2 of the somatosensory
cortex and they had a pyramidal morphology with a single apical dendrite
oriented toward the dorsal cortical surface and at least two basal dendrites.
For each neuron, 15 and 20 optical sections were obtained using 20x and
40x water immersion objectives. Three-dimensional projections were
generated by merging the resulting Z stacks, and the dendritic arbors were
traced using LSM510 software. These traces were analyzed using a customized
matlab script for the automatic counting of branching points, number of
primary dendrites, dendritic length and other topological parameters. Sholl
analysis was also carried out on the Z-stack images. For this analysis,
concentric, digitally generated rings, 15 µm apart, were centered on the
cell soma, and the number of dendrites intersecting each ring was counted
(Sholl, 1953). Pair-wise
comparisons were made using Student's t-test. For multiple
comparisons, ANOVA was performed followed by Fisher's post-hoc test.
For the time course experiments, a total of 10 neurons per condition was scanned 18 hours after transfection. By carefully marking the culture plate orientation and recording the coordinates of the field (as measured with the XY scale of the microscope stage), the same cells were scanned 24 hours later (42 hours of incubation in total). The images were processed and analyzed as above.
MET and HGF RNA levels in cortical slice cultures
The somatosensory cortex was dissected from vibrotome slices and stored at
-70°C. Total RNA was extracted, purified using the BIO101 RNAID kit
(Biogen) and recovered in 40 µl of DEPC-treated water. The RNA was reverse
transcribed for 1 hour at 37°C with MmuLV-reverse transcriptase, RNaseH in
a 40 µl reaction containing the manufacturer's buffer supplemented with 0.5
mM dNTPs and 10 µM random hexanucelitides. A 5 µl aliquot of each
reaction was then amplified in a 30 µl multiplex PCR reaction containing
1xPC buffer (Helena Biosciences), 0.1 mM dNTPs, 2 units of Taq supreme
(Helena Biosciences), 20 µM of GAPDH primers and 200 µM of either HGF or
MET primers. The forward and reverse assay primers for MET cDNA were
5'-CCAGRCCTATATTGATGTC-3' and
5'-TTCGAAGGCATGTATGTAC-3', respectively. The forward and reverse
primers for HGF were 5'-CCCATGAACACAGCTATCGC-3' and
5'-TAAGCGTCCTCTGGATTGC-3', respectively. The cDNAs were amplified
using the following cycling conditions: 1 minute at 95°C, 1 minute at
50°C and 1 minute at 68°C. MET cDNA was amplified for 28 cycles and
HGF cDNA for 26 cycles.
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Results |
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We investigated the potential influence of HGF on dendritic growth and morphology by studying the effect of exogenous HGF on layer 2 pyramidal neurons of the postnatal mouse somatosensory cortex. These neurons were chosen because they are rapidly growing and can be easily observed between P5 and P7 in this region. Stable, high quality labeling of these neurons was observed after 2 days of culture in the mouse brain slice cultures (see Fig. 1A). The dendritic arbors of these neurons were visualized by transfecting them with an EGFP expression plasmid by firing gold particles coated with this plasmid into 300 µm cortical slices. Labeling of layer 2 pyramidal neurons was clearly observed after 12 hours in culture (Fig. 1A), and was stable for at least 2 days. The dendritic morphology of these neurons was conveniently analyzed by constructing a Z stack projection from multiple confocal images taken throughout the dendritic arbor (Fig. 1B).
|
Figure 2 shows a representative sample across the entire range of dendritic morphologies in four experimental conditions: control cultures (no growth factor supplements to the medium) and cultures supplemented with HGF, function-blocking anti-HGF antibody or BDNF. These images illustrate a clearly discernable increase in the size and complexity of pyramidal neuron dendritic arbors in cortical slices treated with either HGF or BDNF for 48 hours compared with control cultures, whereas dendritic arbors in cultures treated with anti-HGF were clearly smaller and less complex than those of control cultures. To quantify dendritic size and complexity, we determined the total number of branch points per arbor, total dendritic length and number of primary dendrites arising from the cell body. Table 1 shows data for total dendritic length and number of branch points for the different experimental conditions. Quantitative ANOVA comparisons showed statistically significant effects among groups in all three morphological indexes. HGF promoted statistically significant increases in total dendrite length (P<0.05) and dendrite branching (P<0.001) compared with control cultures. BDNF promoted similar, statistically significant increases in dendrite growth and branching and, as shown in Fig. 3, additionally promoted a significant increase in the number of primary dendrites (P<0.05). There was also a tendency to an increased number of primary dendrites in the presence of HGF without reaching statistical significance (Fig. 3).
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The growth of pyramidal neuron dendrites is promoted by endogenous HGF
To investigate the physiological significance of endogenous HGF in
regulating the growth and morphology of cortical dendrites, we treated
cultures with a function-blocking anti-HGF antibody. This antibody caused a
statistically significant decrease in the length and branching of pyramidal
dendrites compared with control cultures (P<0.05), although there
was no significant reduction in the total number of primary dendrites
(Fig. 4). This suggests that
endogenously produced HGF plays a role in regulating the growth and morphology
of cortical pyramidal dendrites in the developing cerebral cortex. To
ascertain the specificity of the anti-HGF antibody in this experimental
paradigm, we pre-incubated 200 ng of HGF with either 1 or 3 µm of anti-HGF
antibodies for 1 hour before adding to the cultures (HGF+a1 and HGF+a2,
respectively, in Fig. 3).
Pre-incubation with 1 µg/ml antibody greatly reduced the effects of
exogenous HGF on dendrite growth and branching, and 3 µg/ml antibody
blocked the effects of both endogenous and exogenously added HGF on these two
morphological indexes.
Sholl analysis of dendritic arbors was consistent with the above results and provided complementary quantitative data on the morphological changes brought about by the different experimental conditions. Figure 5 plots the number of dendrite intersections on a series of concentric rings centered on the cell soma of neurons grown under different experimental conditions (HGF, BDNF, HGF + BDNF and anti-HGF) compared with neurons grown under control conditions (no additions). Under all experimental conditions, the number of dendritic intersections initially increased with distance from the cell body to reach a maximum at 45 µm from the cell body, which is indicative of dendritic branching over this distance. Beyond this distance, there was a gradual decrease in the number of intersections with distance, reaching an average of a single process at a distance of 165 µm in control cultures. Figure 5A,B shows that there were significantly more intersections at almost all circles in cultures supplemented with HGF or BDNF compared with control cultures. The increase in number of dendrite intersections between 15 µm and 45 µm was greater in HGF- and BDNF-supplemented cultures compared with control cultures (8 versus 5), but with greater distances this difference between trophic factor-supplemented cultures and control cultures became much less pronounced, suggesting that the enhanced dendritic branching observed in HGF- and BDNF-supplemented cultures is restricted mainly to the proximal regions of the dendritic arbors of cortical neurons. A similar trend was observed in cultures supplemented with HGF plus BDNF, although no additive effect was apparent at any radial distance (Fig. 5C). Anti-HGF treatment resulted in a statistically significant reduction in the overall number of intersections at almost all distances from the soma (Fig. 5D), consistent with a role of endogenous HGF in promoting dendrite branching.
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Slice cultures were bombarded with gold particles coated with the GFP-expressing plasmid plus either an MET KD-expressing vector (gift of Flavio Maina) or an empty control vector. Figure 7 shows a representative sample across the entire range of dendritic morphologies of layer 2 pyramidal neurons expressing the MET KD receptor or transfected with the control vector. These images illustrate a clear decrease in the size and complexity of pyramidal neuron dendritic arbors in neurons expressing the MET KD receptor. Quantification of total dendritic length and total branch number (Table 2) revealed highly statistically significant reductions in MET KD-expressing neurons compared with control transfected neurons (P<0.001). The kinase-dead receptor also significantly reversed the growth-promoting effects of exogenous HGF (Table 2).
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Discussion |
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Several other neurotrophic factors have been shown to affect the growth and
complexity of the pyramidal neuron dendritic arbors in cortical slice
cultures, including BDNF, NT-3, NGF, NT4 and IGF
(Horch et al., 1999;
McAllister et al., 1995
,
1997
;
Niblock et al., 2000
). Because
the TrkB ligands BDNF, NT3 and NT4 have been shown to have a particularly
pronounced effect on dendritic growth in the developing cerebral cortex
(McAllister et al., 1995
), we
undertook a direct comparison of the effects of exogenous BDNF and HGF on the
growth of layer 2 pyramidal neuron dendrites. Although both factors were found
to promote similar overall increases in dendritic length and branching,
analysis of the effects of these factors in the basal and apical dendritic
compartments separately revealed that they display clear differences in their
effects on dendritic morphology. Whereas HGF promotes a generalized increase
in growth and branching, affecting the apical and basal compartments equally,
BDNF has a more pronounced effect on growth and branching of basal dendrites.
In addition, BDNF promotes a modest, though significant, increase in the total
number of primary dendrites. In a study of layer 2 pyramidal neurons in
somatosensory cortical slices of postnatal day 10 rat pups, BDNF was also
found to have a marked effect on the growth and branching of basal dendrites
(Niblock et al., 2000
), but in
contrast to our study, no effect of BDNF on apical dendrites was observed.
Also, in this study, the number of primary dendrites of layer 2 neurons was
unaffected by BDNF. The differences in the effects of BDNF on layer 2
pyramidal dendrites in this study of the postnatal rat cortex and our study of
the postnatal mouse cortex may be because our study was undertaken at an
earlier stage in development when primary dendrites are still sprouting; it is
possible that some aspects of dendritic architecture, such as the number of
primary dendrites, are still plastic and responsive to extracellular signals
early in the differentiation of cortical neurons. Like the generalized effect
of HGF on dendritic growth and branching observed in the present work, IGF was
reported to promote similar increases in dendritic growth and branching in
both apical and basal compartments of layer 2 pyramidal neurons in the
postnatal rat somatosensory cortex
(Niblock et al., 2000
). Our
finding that there is no additional overall dendritic growth and branching in
cultures treated with HGF and BDNF in combination compared with cultures
treated with either factor alone suggests that these factors exert their
actions on the same subset of pyramidal neurons. Taken together, these
findings indicate that HGF and BDNF can influence the growth and morphology of
layer 2 pyramidal neurons of the developing somatosensory cortex in
distinctive ways. Our finding that anti-HGF suppresses dendritic growth and
branching to a similar extent in the apical and basal dendritic compartments
suggests that endogenous HGF exerts a similar influence on the dendritic
arbors of these neurons.
The observed differences in the response of layer 2 pyramidal neurons to
HGF and BDNF in terms of numbers of primary dendrites and morphological
changes in apical and basal dendritic compartments suggests a specific role
for HGF in particular aspects of dendritic development and function. However,
it is also possible that HGF only participates in the general support of
dendritic growth instead of being specifically involved in the fine-tuning of
dendritic architecture. Further work comparing the responses to HGF and those
triggered by neurotrophins and their combinations, as well as comparisons
across different cortical layers, will be needed to address this issue. In
addition to promoting dendrite growth, neurotrophins can also exert negative
effects on the size and complexity of dendritic arbors, and the same factors
can exert opposing actions in different cortical layers. For example, in layer
4 of the developing ferret visual cortex BDNF stimulates growth of pyramidal
dendrites that is inhibited by NT3, whereas in layer 6 NT3 stimulates growth
that is inhibited by BDNF (McAllister et
al., 1997). In future studies it will be of interest to ascertain
whether HGF has markedly different effects on neurons in different cortical
layers, including negative effects on dendritic growth.
During development of the cerebral cortex, both HGF and MET are expressed
as early as E14 and continue to be expressed as the cortical plate matures and
thickens. HGF expression seems to be more intense in the ventral aspects of
the early cortical plate, whereas MET concentrates more in the outermost
layers, a pattern of expression that continues into the postnatal period
(Achim et al., 1997;
Jung et al., 1994
;
Thewke and Seeds, 1999
). In
the adult cortex, neuronal expression of both HGF and MET has been observed in
a layer-specific manner: HGF is expressed in layers 4 and 5, and MET in layers
2, 3, 4 and 5 (Thewke and Seeds,
1999
), suggesting that cortical neurons are able to respond to
endogenous HGF signaling. Here, we observed a morphological change in
pyramidal neurons by manipulating the endogenous availability of HGF,
suggesting a possible direct modulatory role for HGF on dendritic growth. One
possibility is that layer 2 pyramidal neurons may be exposed to HGF
synthesized by neurons with cell bodies that reside in deeper cortical layers
by several possible routes in vivo. Anterograde axonal transport and release
of neurotrophins is now well established (reviewed by
Davies, 2003
), although it is
as yet unknown whether HGF can be transported and released in this manner. In
addition to axonally derived HGF, layer 2 pyramidal neurons could potentially
obtain HGF released by the apical dendrites of pyramidal neurons with cell
bodies that reside deeper in the cortex, or could potentially respond to
endogenous HGF diffusing from deeper cortical layers. An alternative
interpretation is that the regulatory influence of HGF and anti-HGF on
dendrite branching reported here could be indirect, either by influencing the
release of other factors that act directly on pyramidal dendrites or by
influencing the number of presynaptic inputs that are well-characterized
regulators of dendrite growth and branching. Studies of pyramidal neurons
transfected with a kinase-dead, dominant-negative MET receptor showed that the
influence of HGF on dendritic morphology is the result of a direct response of
layer 2 pyramidal neurons to endogenous HGF, demonstrating that HGF directly
regulates the dendritic morphology of these neurons. By contrast to our
result, dendrites of dissociated E18 cortical neurons have been observed not
to respond to exogenous addition of HGF
(Whitford et al., 2002
).
Although the experimental model used in the present study corresponds to a
later stage of development, it could also mean that a more complex set of
regional interactions in the intact cortex is needed for HGF to exert its
normal influence on dendritic development.
HGF has been shown to enhance the growth and branching of neuritic
processes of NGF-dependent sensory and sympathetic neurons in the developing
peripheral nervous system (Maina et al.,
1998; Maina et al.,
1997
; Yang et al.,
1998
), a response that requires the presence of NGF. In our
current study we have provided evidence for a new role for HGF: promoting
dendritic growth and branching in the central nervous system. Whether this
response also requires the cooperation of another neurotrophic factor remains
to be ascertained. Interestingly, it has been shown that cortical slices need
to be electrically active in order to respond to the growth-promoting effects
of BDNF (McAllister et al.,
1996
). It will be important to ascertain in future work whether
the modulatory effects of HGF in the cortex also require neural activity.
Studies of neurons of transgenic mice in which the multifunctional docking
sites of the MET receptor that bind phosphatidylinositol-3 kinase (PI3K), SRC,
GRB2 and GAB1 have been converted into optimal binding motifs for either PI3K,
SRC, or GRB2 have shown that the neurite growth-promoting effects of HGF are
dependent on binding and activation of PI3K
(Maina et al., 2001
). Whether
this is the case for the effects of HGF on dendritic growth in the cerebral
cortex remains to be ascertained, as the use of these mutants is hampered by
their failure to survive until birth.
The present findings demonstrate that HGF plays a role in regulating the morphology of cortical pyramidal dendrites in the early postnatal period and that endogenous levels of HGF are necessary for the normal development of these neurons. Our findings provide further support for the notion that HGF enhances neural maturation throughout the entire neuraxis.
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ACKNOWLEDGMENTS |
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Footnotes |
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Present address: Lab Anatomia patologica-genetica, Hospital Arnau de
Vilanova, Av Rovira Rourre, 80, 25198 Lleida, Spain
Present address: Department Anatomy and Cell Biology, University of
Melbourne, Parkville, Victoria 3010, Australia
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Achim, C. L., Katyal, S., Wiley, C. A., Shiratori, M., Wang, G., Oshika, E., Petersen, B. E., Li, J. M. and Michalopoulos, G. K. (1997). Expression of HGF and cMet in the developing and adult brain. Dev. Brain Res. 102,299 -303.[CrossRef][Medline]
Andermarcher, E., Surani, M. A. and Gherardi, E. (1996). Co-expression of the HGF/SF and c-met genes during early mouse embryogenesis precedes reciprocal expression in adjacent tissues during organogenesis. Dev. Genet. 18,254 -266.[CrossRef][Medline]
Birchmeier, C. and Gherardi, E. (1998). Developmental role of HGF/SF and its receptor, the c-Met tyrosine kinase. Trends Cell Biol. 8,404 -410.[CrossRef][Medline]
Bladt, F., Riethmacher, D., Isenmann, S., Aguzzi, A. and Birchmeier, C. (1995). Essential role for the met receptor and the migration of myogenic precursor cells into the limb bud. Nature 376,768 -771.[CrossRef][Medline]
Bonner-Fraser, M. (1995). Hepatocyte growth factor/scatter factor (HGF/SF) in early development: evidence for a role in neuronal induction. Trends Genet. 11,423 -425.[CrossRef][Medline]
Davey, F., Hilton, M. and Davies, A. M. (2000). Cooperation between HGF and CNTF in promoting the survival and growth of sensory and parasympathetic neurons. Mol. Cell. Neurosci. 15,79 -87.[CrossRef][Medline]
Davies, A. M. (2003). Regulation of neuronal
survival and death by extracellular signals during development.
EMBO J. 22,2537
-2545.
Di Renzo, M. F., Bertolotto, A., Olivero, M., Putzolu, P., Crepaldi, T., Schiffer, D., Pagni, C. A. and Comoglio, P. M. (1993). Selective expression of the Met/HGF receptor in human central nervous system microglia. Oncogene 8, 219-222.[Medline]
Ebens, A., Brose, K., Leonardo, E. D., Hanson, M. G., Bladt, F., Birchmeier, C., Barres, B. A. and Tessier-Lavigne, M. (1996). Hepatocyte Growth Factor/Scatter Factor is an axonal chemoattractant and a neurotrophic factor for spinal motor neurons. Neuron 17,1157 -1172.[Medline]
Gherardi, E. and Stoker, M. (1991). Hepatocyte growth factor-scatter factor: mitogen, motogen and met. Cancer Cells 3,227 -232.[Medline]
Hamanoue, M., Tekemoto, N., Matsumoto, J., Nakamura, T., Nakajima, K. and Kohsaka, S. (1996). Neurotrophic effect of hepatocyte growth factor on central nervous system in vitro. J. Neurosci. Res. 43,554 -564.[CrossRef][Medline]
Hayar, T. F., Bambrick, L. L., Krueger, B. K. and Rakic, P. (1999). Organotypic slice cultures for analysis of proliferation, dell death, and migration in the embryonic neocortex. Brain Res. Brain Res. Protoc. 4,425 -437.[CrossRef][Medline]
Honda, S., Kagoshima, M., Wanaka, A., Tohoyama, M., Matsumoto, K. and Nakamura, T. (1995). Localization and functional coupling of HGF and c-met/HGF receptor in rat brain: implication as neurotrophic factor. Mol. Brain Res. 32,197 -210.[CrossRef][Medline]
Horch, H. W., Kruttgen, A., Portbury, S. D. and Katz, L. C. (1999). Destabilization of cortical dendrites and spines by BDNF. Neuron 23,353 -364.[Medline]
Ieraci, A., Forni, P. E. and Ponzetto, C.
(2002). Viable hypomorphic signaling mutant of the Met receptor
reveals a role for hepatocyte growth factor in postnatal cerebellar
development. Proc. Natl. Acad. Sci. USA
99,15200
-15205.
Jung, W., Castren, E., Odenthal, M., VandeWoude, G. F., Ishii, T., Dienes, H. P. and Shirmacher, P. (1994). Expression and functional interaction of hepatocyte growth factor/scatter factor and its receptor c-met in mammalian brain. J. Cell Biol. 126,485 -494.[Abstract]
Korhonen, L., Sjöholm, U., Takei, N., Kern, M. A., Shirmacher, P., Castren, E. and Lindholm, D. (2000). Expression of c-Met in developing rat hippocampus: evidence for HGF as a neurotrophic factor for calbindin D-expressing neurons. Eur. J. Neurosci. 12,3453 -3461.[CrossRef][Medline]
Krasnoselsky, A., Massay, M. J., DeFrances, M. C., Michalopoulos, G., Zarnegar, R. and Ratner, N. (1994). Hepatocyte growth factor is a mitogen for Schwann cells and is present in neurofibromas. J. Neurosci. 14,7284 -7290.[Abstract]
Maina, F. and Klein, R. (1999). Hepatocyte growth factor, a versatile signal for developing neurons. Nat. Neurosci. 2,213 -217.[CrossRef][Medline]
Maina, F., Casagranda, F., Audero, E., Simeone, A., Comologlio, P. M., Klein, R. and Ponzetto, C. (1996). Ucoupling of Grb2 from the met receptor in vivo reveals complex roles in muscle development. Cell 87,531 -542.[Medline]
Maina, F., Hilton, M. C., Andres, R., Wyatt, S., Klein, R. and Davies, A. M. (1998). Multiple roles for hepatocyte growth factor in sympathetic neuron development. Neuron 20,835 -846.[Medline]
Maina, F., Hilton, M. C., Ponzetto, C., Davies, A. M. and Klein,
R. (1997). Met receptor signalling is required for sensory
nerve development. Genes Dev.
11,3341
-3350.
Maina, F., Pante, G., Helmbacher, F., Andres, R., Porthin, A., Davies, A. M., Ponzetto, C. and Klein, R. (2001). Coupling Met to specific pathways result in distinct developmental outcomes. Mol. Cell 7,1293 -1306.[CrossRef][Medline]
McAllister, A. K., Katz, L. C. and Lo, D. C. (1996). Neurotrophin regulation of cortical dendritic growth requires activity. Neuron 17,1057 -1064.[Medline]
McAllister, A. K., Katz, L. C. and Lo, D. C. (1997). Opposing role for endogenous BDNF and NT-3 in regulating cortical dendritic growth. Neuron 18,767 -778.[Medline]
McAllister, A. K., Lo, D. C. and Katz, L. W. (1995). Neurotrophins regulate dendritic grewth in developing visual cortex. Neuron 15,791 -803.[Medline]
Miyazawa, T., Matsumoto, K., Ohmichi, H., Katoh, H., Yamashima, T. and Nakamura, T. (1998). Protection of hippocampal neurons from ischemia-induced delayed neuronal death by hepatocyte growth factor: a novel neurotrophic factor. J. Cereb. Blood Flow Metab. 18,345 -348.[Medline]
Niblock, M. N., Brunso-Bechtold, J. K. and Riddle, D. R.
(2000). Insuline-like growth factor I stimulates dendritic growth
in primary somatosensory cortex. J. Neurosci.
20,4165
-4176.
Ponzzeto, C., Bardelli, A., Zhen, Z., Maina, F., dalla-Zonca, P., Giordano, S., Graziani, A., Panayotou, G. and Comoglio, P. M. (1994). A multifunctional Docking site medites signaling and transformation by the Hepatocyte Growth Factor/Scatter Factor receptor family. Cell 77,261 -271.[Medline]
Powell, E. M., Mars, W. M. and Levitt, P. (2001). Hepatocyte growth factor/scatter factor is a motogen for interneurons migrating from the ventral to dorsal telencephalon. Neuron 30,79 -89.[Medline]
Schmidt, C., Bladt, F., Goedecke, S., Brinkmann, V., Zschiesche, W., Sharpe, M., Gherardi, E. and Birchmeier, C. (1995). Scatter factor/Hepatociyte growth factor is essential for liver development. Nature 373,699 -702.[CrossRef][Medline]
Sholl, D. A. (1953). Dendritic organization in the neurons of the visual and motor cortices of the cat. J. Anat. 87,387 -406.[Medline]
Sonnenberg, E., Meyer, D., Weidner, K. M. and Birchmeier, C. (1993). Scatter factor/hepatoycte growth factor and its receptor, the met tyrosine kinase, can mediate a signal exchange between mesenchyme and epithelia during mouse development. J. Cell Biol. 123,223 -235.[Abstract]
Tan, J. C., Nocka, K., Ray, P., Traktman, P. and Besmer, P. (1990). The dominant W42 spotting phenotype results from a missense mutation in the c-kit receptor kinase. Science 247,209 -212.[Medline]
Thewke, D. P. and Seeds, N. W. (1999). The expression of mRNA for hepatocyte grewth factor/scatter factor, its receptor c-met, and one of its activators tissue-type plasminogen activator show a systematic relationship in the developing and adult cerebral cortex and hippocampus. Brain Res. 821,356 -367.[CrossRef][Medline]
Tsarfaty, I., Resau, J. H., Rulong, S., Keydar, U., Faletto, D. L. and VandeWoude, G. F. (1992). The met proto-oncogene receptor and lumen formation. Science 257,1258 -1261.[Medline]
Uehara, Y., Minowa, O., Mori, C., Shiota, K., Kuno, J., Noda, T. and Kitamura, N. (1995). Placental defect and embrionic lethality in mice lacking hepatocyte growth factor/Scatter factor. Nature 373,702 -705.[CrossRef][Medline]
Whitford, K. L., Marillat, V., Stein, E., Goodman, C. S., Tessier-Lavigne, M., Chedotail, A. and Ghosh, A. (2002). Regulation of cortical dendrite development by Slit-Robo interactions. Neuron 22,47 -61.[CrossRef]
Wong, V., Glass, D. J., Arriaga, R., Yancopoulos, G. D.,
Lindsay, R. M. and Conn, G. (1997). Hepatocyte growth factor
promotes motor neuron survival and synergises with ciliary neurotrophic
factor. J. Biol. Chem.
272,5187
-5191.
Yamamoto, Y., Livet, J., Vesjsada, R., Pollock, R. A., Arce, V.,
delaPeyere, O., A. C. Kato and Henderson, C. E. (1997).
Hepatocyte growth factor (HGF/SF) is an essential muscle derived survival
factor for a subpopulation of embryonic motoneurons.
Development 124,2903
-2913.
Yang, X. M., Toma, J. G., Bamji, S. X., Velliveau, D. J., Khon,
J., Park, M. and Miller, F. D. (1998). Autocrine hepatocyte
greowth factor provides a local mechanism for promoting axonal growth.
J. Neurosci. 18,8369
-8381.
Zhang, L., Himi, T., Morita, I. and Murota, S. (2000). Hepatocyte growth factor protects cultured rat cerebellar granule neurons via the phosphatidylinositol-3 kinase pathway/Akt pathway. J. Neurosci. 59,489 -496.[CrossRef]