scholarly journals Axonal filopodial asymmetry induced by synaptic target

2011 ◽  
Vol 22 (14) ◽  
pp. 2480-2490 ◽  
Author(s):  
Pan P. Li ◽  
Cheng Chen ◽  
Chi-Wai Lee ◽  
Raghavan Madhavan ◽  
H. Benjamin Peng
Keyword(s):  
Acetylcholine Receptors ◽  
Short Range ◽  
Selective Inhibitor ◽  
Dominant Negative ◽  
Normal Density ◽  
Fibroblast Growth ◽  
Wild Type ◽  
Spinal Neurons ◽  
Fgf Receptor ◽  
Nerve Muscle

During vertebrate neuromuscular junction (NMJ) assembly, motor axons and their muscle targets exchange short-range signals that regulate the subsequent steps of presynaptic and postsynaptic specialization. We report here that this interaction is in part mediated by axonal filopodia extended preferentially by cultured Xenopus spinal neurons toward their muscle targets. Immunoblotting and labeling experiments showed that basic fibroblast growth factor (bFGF) was expressed by muscle and associated with the cell surface, and treatment of cultured spinal neurons with recombinant bFGF nearly doubled the normal density of filopodia in neurites. This effect of bFGF was abolished by SU5402, a selective inhibitor of FGF-receptor 1 (FGFR1), and forced expression of wild-type or dominant-negative FGFR1 in neurons enhanced or suppressed the assembly of filopodia, respectively. Significantly, in nerve–muscle cocultures, knocking down bFGF in muscle decreased both the asymmetric extension of filopodia by axons toward muscle and the assembly of NMJs. In addition, neurons expressing dominant-negative FGFR1 less effectively triggered the aggregation of muscle acetylcholine receptors at innervation sites than did control neurons. These results suggest that bFGF activation of neuronal FGFR1 generates filopodial processes in neurons that promote nerve–muscle interaction and facilitate NMJ establishment.

Induction of the mesendoderm in the zebrafish germ ring by yolk cell-derived TGF-beta family signals and discrimination of mesoderm and endoderm by FGF

Development ◽  
1999 ◽  
Vol 126 (14) ◽  
pp. 3067-3078 ◽  
Author(s):  
A. Rodaway ◽  
H. Takeda ◽  
S. Koshida ◽  
J. Broadbent ◽  
B. Price ◽  
...  
Keyword(s):  
Ectopic Expression ◽  
Dominant Negative ◽  
Fibroblast Growth ◽  
Tgf Beta ◽  
Fgf Receptor ◽  
Activin Receptor ◽  
Yolk Cell ◽  
Endogenous Expression ◽  
Vertebrate Embryo ◽  
Fgf Signalling

The endoderm forms the gut and associated organs, and develops from a layer of cells which emerges during gastrula stages in the vertebrate embryo. In comparison to mesoderm and ectoderm, little is known about the signals which induce the endoderm. The origin of the endoderm is intimately linked with that of mesoderm, both by their position in the embryo, and by the molecules that can induce them. We characterised a gene, zebrafish gata5, which is expressed in the endoderm from blastula stages and show that its transcription is induced by signals originating from the yolk cell. These signals also induce the mesoderm-expressed transcription factor no tail (ntl), whose initial expression coincides with gata5 in the cells closest to the blastoderm margin, then spreads to encompass the germ ring. We have characterised the induction of these genes and show that ectopic expression of activin induces gata5 and ntl in a pattern which mimics the endogenous expression, while expression of a dominant negative activin receptor abolishes ntl and gata5 expression. Injection of RNA encoding a constitutively active activin receptor leads to ectopic expression of gata5 and ntl. gata5 is activated cell-autonomously, whereas ntl is induced in cells distant from those which have received the RNA, showing that although expression of both genes is induced by a TGF-beta signal, expression of ntl then spreads by a relay mechanism. Expression of a fibroblast growth factor (eFGF) or a dominant negatively acting FGF receptor shows that ntl but not gata5 is regulated by FGF signalling, implying that this may be the relay signal leading to the spread of ntl expression. In embryos lacking both squint and cyclops, members of the nodal group of TGF-beta related molecules, gata5 expression in the blastoderm is abolished, making these factors primary candidates for the endogenous TGF-beta signal inducing gata5.

scholarly journals The function of p120 catenin in filopodial growth and synaptic vesicle clustering in neurons

2012 ◽  
Vol 23 (14) ◽  
pp. 2680-2691 ◽  
Author(s):  
Cheng Chen ◽  
Pan P. Li ◽  
Raghavan Madhavan ◽  
H. Benjamin Peng
Keyword(s):  
Synaptic Vesicle ◽  
Motor Neurons ◽  
Rho Gtpases ◽  
Acetylcholine Receptors ◽  
Physical Contact ◽  
Spinal Neurons ◽  
P120 Catenin ◽  
Presynaptic Differentiation ◽  
Nerve Muscle ◽  
Postsynaptic Differentiation

At the developing neuromuscular junction (NMJ), physical contact between motor axons and muscle cells initiates presynaptic and postsynaptic differentiation. Using Xenopus nerve–muscle cocultures, we previously showed that innervating axons induced muscle filopodia (myopodia), which facilitated interactions between the synaptic partners and promoted NMJ formation. The myopodia were generated by nerve-released signals through muscle p120 catenin (p120ctn), a protein of the cadherin complex that modulates the activity of Rho GTPases. Because axons also extend filopodia that mediate early nerve–muscle interactions, here we test p120ctn's function in the assembly of these presynaptic processes. Overexpression of wild-type p120ctn in Xenopus spinal neurons leads to an increase in filopodial growth and synaptic vesicle (SV) clustering along axons, whereas the development of these specializations is inhibited following the expression of a p120ctn mutant lacking sequences important for regulating Rho GTPases. The p120ctn mutant also inhibits the induction of axonal filopodia and SV clusters by basic fibroblast growth factor, a muscle-derived molecule that triggers presynaptic differentiation. Of importance, introduction of the p120ctn mutant into neurons hinders NMJ formation, which is observed as a reduction in the accumulation of acetylcholine receptors at innervation sites in muscle. Our results suggest that p120ctn signaling in motor neurons promotes nerve–muscle interaction and NMJ assembly.

scholarly journals Activin-mediated mesoderm induction requires FGF

Development ◽  
1994 ◽  
Vol 120 (2) ◽  
pp. 453-462 ◽  
Author(s):  
R.A. Cornell ◽  
D. Kimelman
Keyword(s):  
Dominant Negative ◽  
Mesoderm Induction ◽  
Fibroblast Growth ◽  
Fgf Signaling ◽  
Tgf Beta ◽  
Fgf Receptor ◽  
Basic Fgf ◽  
Dominant Negative Form ◽  
Negative Form

The early patterning of mesoderm in the Xenopus embryo requires signals from several intercellular factors, including mesoderm-inducing agents that belong to the fibroblast growth factor (FGF) and TGF-beta families. In animal hemisphere explants (animal caps), basic FGF and the TGF-beta family member activin are capable of converting pre-ectodermal cells to a mesodermal fate, although activin is much more effective at inducing dorsal and anterior mesoderm than is basic FGF. Using a dominant-negative form of the Xenopus type 1 FGF receptor, we show that an FGF signal is required for the full induction of mesoderm by activin. Animal caps isolated from embryos that have been injected with the truncated FGF receptor and cultured with activin do not extend and the induction of some genes, including cardiac actin and Xbra, is greatly diminished, while the induction of other genes, including the head organizer-specific genes gsc and Xlim-1, is less sensitive. These results are consistent with the phenotype of the truncated FGF receptor-injected embryo and imply that the activin induction of mesoderm depends on FGF, with some genes requiring a higher level of FGF signaling than others.

scholarly journals Compound deletion of Fgfr3 and Fgfr4 partially rescues the Hyp mouse phenotype

2011 ◽  
Vol 300 (3) ◽  
pp. E508-E517 ◽  
Author(s):  
Hua Li ◽  
Aline Martin ◽  
Valentin David ◽  
L. Darryl Quarles
Keyword(s):  
Phosphate Transport ◽  
Current Data ◽  
Fibroblast Growth ◽  
Wild Type ◽  
Compensatory Response ◽  
Fgf Receptor ◽  
Dihydroxyvitamin D ◽  
1,25 Dihydroxyvitamin D ◽  
Fgfr1 Expression ◽  
Stimulation Of

Uncertainty exists regarding the physiologically relevant fibroblast growth factor (FGF) receptor (FGFR) for FGF23 in the kidney and the precise tubular segments that are targeted by FGF23. Current data suggest that FGF23 targets the FGFR1c-Klotho complex to coordinately regulate phosphate transport and 1,25-dihydroxyvitamin D [1,25(OH)2D] production in the proximal tubule. In studies using the Hyp mouse model, which displays FGF23-mediated hypophosphatemia and aberrant vitamin D, deletion of Fgfr3 or Fgfr4 alone failed to correct the Hyp phenotype. To determine whether FGFR1 is sufficient to mediate the renal effects of FGF23, we deleted Fgfr3 and Fgfr4 in Hyp mice, leaving intact the FGFR1 pathway by transferring compound Fgfr3/Fgfr4-null mice on the Hyp background to create wild-type (WT), Hyp, Fgfr3−/−/Fgfr4−/−, and Hyp/Fgfr3−/−/Fgfr4−/− mice. We found that deletion of Fgfr3 and Fgfr4 in Fgfr3−/−/Fgfr4−/− and Hyp/Fgfr3−/−/Fgfr4−/− mice induced an increase in 1,25(OH)2D. In Hyp/Fgfr3−/−/Fgfr4−/− mice, it partially corrected the hypophosphatemia (Pi = 9.4 ± 0.9, 6.1 ± 0.2, 9.1 ± 0.4, and 8.0 ± 0.5 mg/dl in WT, Hyp, Fgfr3−/−/Fgfr4−/−, and Hyp/Fgfr3−/−/Fgfr4−/− mice, respectively), increased Na-phosphate cotransporter Napi2a and Napi2c and Klotho mRNA expression in the kidney, and markedly increased serum FGF23 levels (107 ± 20, 3,680 ± 284, 167 ± 22, and 18,492 ± 1,547 pg/ml in WT, Hyp, Fgfr3−/−/Fgfr4−/−, and Hyp/Fgfr3−/−/Fgfr4−/− mice, respectively), consistent with a compensatory response to the induction of end-organ resistance. Fgfr1 expression was unchanged in Hyp/Fgfr3−/−/Fgfr4−/− mice and was not sufficient to transduce the full effects of FGF23 in Hyp/Fgfr3−/−/Fgfr4−/− mice. These studies suggest that FGFR1, FGFR3, and FGFR4 act in concert to mediate FGF23 effects on the kidney and that loss of FGFR function leads to feedback stimulation of Fgf23 expression in bone.

scholarly journals Spatial response to fibroblast growth factor signalling in Xenopus embryos

Development ◽  
1999 ◽  
Vol 126 (1) ◽  
pp. 119-125 ◽  
Author(s):  
B. Christen ◽  
J.M. Slack
Keyword(s):  
Growth Factors ◽  
Source Region ◽  
Dominant Negative ◽  
Fibroblast Growth ◽  
Fgf Receptor ◽  
Erk Activation ◽  
Activation Domains ◽  
Stage Of Development ◽  
Fgf Signalling

We have examined the spatial pattern of activation of the extracellular signal-regulated protein kinase (ERK) during Xenopus development, and show that it closely resembles the expression of various fibroblast growth factors (FGFs). Until the tailbud stage of development, all ERK activation domains are sensitive to the dominant negative FGF receptor, showing that activation is generated by endogenous FGF signalling. ERK is not activated by application of other growth factors like BMP4 or activin, nor is endogenous activation blocked by the respective dominant negative receptors. This shows that various domains of FGF expression, including the periblastoporal region and the midbrain-hindbrain boundary, are also sites of FGF signalling in vivo. Wounding induces a transient (<60 minutes) activation of ERK which is not significantly reduced by the dominant negative FGF receptor. An artificial FGF source, created by injection of eFGF mRNA into cleavage stage embryos, provokes ERK activation outside of its injection site over a range of several cell diameters. The range and extent of ERK activation outside the source region is unchanged by co-injection of a dominant negative form of Ras, which blocks ERK-activation within the source. This suggests that FGF protein can diffuse over several cell diameters.

scholarly journals Reduced Mobility of Fibroblast Growth Factor (FGF)-Deficient Myoblasts Might Contribute to Dystrophic Changes in the Musculature of FGF2/FGF6/mdx Triple-Mutant Mice

2003 ◽  
Vol 23 (17) ◽  
pp. 6037-6048 ◽  
Author(s):  
Petra Neuhaus ◽  
Svetlana Oustanina ◽  
Tomasz Loch ◽  
Marcus Krüger ◽  
Eva Bober ◽  
...  
Keyword(s):  
Muscle Regeneration ◽  
Dominant Negative ◽  
Skeletal Muscle Regeneration ◽  
Mdx Mice ◽  
Fibroblast Growth ◽  
Wild Type ◽  
Triple Mutant ◽  
Migration Ability ◽  
Critical Components

ABSTRACT Development and regeneration of muscle tissue is a highly organized, multistep process that requires cell proliferation, migration, differentiation, and maturation. Previous data implicate fibroblast growth factors (FGFs) as critical regulators of these processes, although their precise role in vivo is still not clear. We have explored the consequences of the loss of multiple FGFs (FGF2 and FGF6 in particular) for muscle regeneration in mdx mice, which serve as a model for chronic muscle damage. We show that the combined loss of FGF2 and FGF6 leads to severe dystrophic changes in the musculature. We found that FGF6 mutant myoblasts had decreased migration ability in vivo, whereas wild-type myoblasts migrated normally in a FGF6 mutant environment after transplantation of genetically labeled myoblasts from FGF6 mutants in wild-type mice and vice versa. In addition, retrovirus-mediated expression of dominant-negative versions of Ras and Ral led to a reduced migration of transplanted myoblasts in vivo. We propose that FGFs are critical components of the muscle regeneration machinery that enhance skeletal muscle regeneration, probably by stimulation of muscle stem cell migration.

scholarly journals RhoD activated by fibroblast growth factor induces cytoneme-like cellular protrusions through mDia3C

2012 ◽  
Vol 23 (23) ◽  
pp. 4647-4661 ◽  
Author(s):  
Kazuhisa Koizumi ◽  
Kazunori Takano ◽  
Akiko Kaneyasu ◽  
Haruko Watanabe-Takano ◽  
Emi Tokuda ◽  
...  
Keyword(s):  
Growth Factor ◽  
Fibroblast Growth Factor ◽  
Actin Polymerization ◽  
Focal Adhesions ◽  
Small Gtpase ◽  
Fibroblast Growth ◽  
Wild Type ◽  
Fgf Receptor ◽  
Early Endosomes ◽  
Stimulation Of

The small GTPase RhoD regulates actin cytoskeleton to collapse actin stress fibers and focal adhesions, resulting in suppression of cell migration and cytokinesis. It also induces alignment of early endosomes along actin filaments and reduces their motility. We show here that a constitutively activated RhoD generated two types of actin-containing thin peripheral cellular protrusions distinct from Cdc42-induced filopodia. One was longer, almost straight, immotile, and sensitive to fixation, whereas the other was shorter, undulating, motile, and resistant to fixation. Moreover, cells expressing wild-type RhoD extended protrusions toward fibroblast growth factor (FGF) 2/4/8–coated beads. Stimulation of wild-type RhoD-expressing cells with these FGFs also caused formation of cellular protrusions. Nodules moved through the RhoD-induced longer protrusions, mainly toward the cell body. Exogenously expressed FGF receptor was associated with these moving nodules containing endosome-like vesicles. These results suggest that the protrusions are responsible for intercellular communication mediated by FGF and its receptor. Accordingly, the protrusions are morphologically and functionally equivalent to cytonemes. RhoD was activated by FGF2/4/8. Knockdown of RhoD interfered with FGF-induced protrusion formation. Activated RhoD specifically bound to mDia3C and facilitated actin polymerization together with mDia3C. mDia3C was localized to the tips or stems of the protrusions. In addition, constitutively activated mDia3C formed protrusions without RhoD or FGF stimulation. Knockdown of mDia3 obstructed RhoD-induced protrusion formation. These results imply that RhoD activated by FGF signaling forms cytoneme-like protrusions through activation of mDia3C, which induces actin filament formation.

scholarly journals Targeted Expression of a Dominant-Negative Fibroblast Growth Factor (FGF) Receptor in Gonadotropin-Releasing Hormone (GnRH) Neurons Reduces FGF Responsiveness and the Size of GnRH Neuronal Population

2005 ◽  
Vol 19 (1) ◽  
pp. 225-236 ◽  
Author(s):  
Pei-San Tsai ◽  
Suzanne M. Moenter ◽  
Hector R. Postigo ◽  
Mohammed El Majdoubi ◽  
Toni R. Pak ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Neuronal Cell ◽  
Neuronal Population ◽  
Dominant Negative ◽  
Delayed Puberty ◽  
Fibroblast Growth ◽  
Gnrh Neuron ◽  
Fgf Receptor ◽  
Gnrh Neurons ◽  
A Cell

Abstract Increasing evidence suggests that fibroblast growth factors (FGFs) are neurotrophic in GnRH neurons. However, the extent to which FGFs are involved in establishing a functional GnRH system in the whole organism has not been investigated. In this study, transgenic mice with the expression of a dominant-negative FGF receptor mutant (FGFRm) targeted to GnRH neurons were generated to examine the consequence of disrupted FGF signaling on the formation of the GnRH system. To first test the effectiveness of this strategy, GT1 cells, a GnRH neuronal cell line, were stably transfected with FGFRm. The transfected cells showed attenuated neurite outgrowth, diminished FGF-2 responsiveness in a cell survival assay, and blunted activation of the signaling pathway in response to FGF-2. Transgenic mice expressing FGFRm in a GnRH neuron-specific manner exhibited a 30% reduction in GnRH neuron number, but the anatomical distribution of GnRH neurons was unaltered. Although these mice were initially fertile, they displayed several reproductive defects, including delayed puberty, reduced litter size, and early reproductive senescence. Overall, our results are the first to show, at the level of the organism, that FGFs are one of the important components involved in the formation and maintenance of the GnRH system.

scholarly journals Essential Role of Fibroblast Growth Factor Signaling in Preadipoctye Differentiation

2005 ◽  
Vol 90 (2) ◽  
pp. 1226-1232 ◽  
Author(s):  
Nayan G. Patel ◽  
Sudhesh Kumar ◽  
Margaret C. Eggo
Keyword(s):  
Recombinant Adenovirus ◽  
Specific Inhibitor ◽  
Tissue Growth ◽  
Dominant Negative ◽  
Growth Factor Signaling ◽  
Fibroblast Growth ◽  
Fgf Receptor ◽  
Human Preadipocytes

We have examined the expression and role of autocrine fibroblast growth factors (FGFs) in human preadipocytes through their differentiation in vitro. A high-molecular weight form of FGF-2 was initially strongly expressed, but 6–9 d after induction of differentiation, its expression decreased markedly. This coincided with the first appearance of visible lipid droplets within the cells. FGF-2 (18 kDa) was not found. FGF receptor (FGFR) 1 was detected as a single band of 125 kDa that also decreased with differentiation. Its decrease preceded that of FGF-2. Despite the decrease in cell-associated FGF-2 with differentiation, secreted FGF-2 was 2.5-fold higher in the differentiated preadipocytes. To determine whether FGF-2 had an autocrine role, FGFR signaling was inhibited using recombinant adenovirus expressing dominant negative FGFR1 (RAdDN-FGFR1) and a specific inhibitor of FGFR1 signaling, PD166866. Preadipocytes transduced with RAdDN-FGFR1 expressed a truncated, 79-kDa FGFR1. Differentiation, assessed by lipid droplet formation, was completely prevented by RAdDN-FGFR1 and by PD166866. The protein content in the cell layer and glucose uptake were significantly reduced by both agents. The insulin-sensitizing drug, rosiglitazone, did not prevent the actions of RAdDN-FGFR1 or PD166866. Controlling adipose tissue growth by limiting FGF actions may provide a means to combat obesity.

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