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Molecular and Cellular Biology, March 2000, p. 2260-2268, Vol. 20, No. 6
Departments of
Microbiology1 and
Pathology,2 New York University
School of Medicine, New York, New York 10016
Received 20 December 1999/Accepted 23 December 1999
Fibroblast growth factor 1 (FGF1) and FGF2, the prototypic members
of the FGF family of growth factors, have been implicated in a variety
of physiological and pathological processes. Unlike most other FGFs,
FGF1 and FGF2 are ubiquitously expressed and are not efficiently
secreted. Gene knockouts in mice have previously demonstrated a role
for FGF2 in brain development, blood pressure regulation, and wound
healing. The relatively mild phenotypic defects associated with FGF2
deletion led to the hypothesis that the continued expression of other
FGFs partially compensated for the absence of FGF2 in these mice. We
now report our generation of mice lacking FGF1 and their use, in
combination with our previously described FGF2 null mice, to produce
mice lacking both FGF1 and FGF2. FGF1-FGF2 double-knockout mice are
viable and fertile and do not display any gross phenotypic defects. In
the double-knockout mice we observed defects that were similar in
extent to those previously described for the FGF2 null mice.
Differences in the organization of neurons of the frontal motor cortex
and in the rates of wound healing were observed. We also observed in
FGF2 Fibroblast growth factors (FGFs)
comprise a widely expressed and multifunctional family of polypeptides.
FGFs transduce signals that can regulate cell growth, migration,
differentiation, or survival. The biological activity of FGFs is
mediated through interactions with transmembrane tyrosine kinase
receptors. Four different receptors for FGFs are known, although each
is present in multiple isoforms owing to alternative splicing of the
mRNA. For the most part, there is no one-to-one correspondence between FGF ligands and receptors. A given FGF may be capable of multiple receptor isoforms; conversely, any receptor variant may bind multiple FGFs (3, 8, 19).
FGF signaling has been implicated in a variety of physiological and
pathological processes, ranging from angiogenesis to tumor progression.
To date, however, the most clearly demonstrated role of FGF signaling
is in development. Studies using knockout mice have demonstrated
essential functions for FGF receptor 1 (FGFR1) and FGFR2 in early
development (1, 12, 40, 41) and roles for FGFR3 in skeletal
morphogenesis (9, 11). Studies of mice lacking individual
FGFs reveal a variety of phenotypes which range from early embryonic
lethality to very mild defects (14, 16, 17, 22, 23, 27, 30, 31,
34, 42). These findings most likely reflect the redundancy of the
FGF family of ligands or their uniqueness of expression in specific tissues.
A total of 22 different FGF molecules have been described so far,
although four of them (FGF-homologous factors [FHFs] FGF11 to -14)
(37) may not be canonical FGFs. FGF1 and FGF2 were the first
to be isolated and were originally named acidic and basic FGF,
respectively, based on their isoelectric points. Despite their status
as the "prototypic" FGF family members, FGF1 and FGF2 differ from
most other FGFs in several important ways. FGF1 is unique among FGFs in
that it binds with high affinity to all known receptor isoforms
(33). Although many FGFs exhibit limited spatial or temporal
expression patterns, mRNAs for FGF1 and FGF2 are detectable in a
variety of tissues during both development and adulthood. FGF1 and FGF2
lack a signal peptide at their 5' ends and are found in the cytosol;
however, both factors seem to be released from cells through a
nonclassical secretory pathway (6, 8). Intriguingly, both
FGF1 and FGF2 have also been found in the cell nucleus. A putative
nuclear localization signal has been identified at the 5' end of the
FGF1 protein (24), and alternative translation initiation
sites in the 5' region of the FGF2 gene give rise to
higher-molecular-weight forms of the protein that localize to the
nucleus (6, 7). The precise function(s) of these nuclear
forms of FGF1 and FGF2 remains unclear.
There is evidence suggesting a role for FGF1 and FGF2 in the proper
development and maintenance of neuronal tissue. Both FGFs are highly
expressed in adult brain, although each factor localizes to a different
neuronal subpopulation. Expression of FGF1 has been detected in sensory
and motor neurons, as well as in the substantia nigra, cholinergenic
neurons of the basal forebrain, and several other subcortical neuronal
populations. In contrast, FGF2 expression is found primarily in
astrocytes and pyramidal neurons of the hippocampus (see reference
15 and references cited therein). A potential role
for FGFs in brain development is suggested by the observation that FGF2
can induce neuroectoderm formation and can establish regional
neuroectodermal identities along the anteroposterior axis when provided
exogenously to gastrula and early-neurula-stage frog embryos
(21). In vitro, FGF2 induces astrocytes to reenter the cell
cycle and induces markers of differentiation (25). FGF2
promotes the outgrowth of cultured hippocampal and cortical neurons
(28) and regulates the expression of certain neurotransmitters (2). FGF2 can also stimulate division of cortical stem cells and may promote differentiation of postmitotic neurons (20, 35, 38).
FGFs have been postulated to play a major role in wound healing, with
particular focus on potential roles for FGF1, FGF2, and FGF7. FGFs
promote angiogenesis as well as stimulate proliferation of many cell
types involved in wound healing, including endothelial cells,
fibroblasts, and keratinocytes (4, 5). Topical application of FGF1 and FGF2 accelerates wound healing in a number of animal models
(29, 32). Many of the cell types active in wound healing that are responsive to FGFs are themselves capable of secreting FGFs
and other cytokines, raising the possibility of highly complex and
regulated interactions between a variety of cell types.
Members of the FGF family have also been shown to play a role in
hematopoiesis. They can synergize with hematopoietic cytokines to
promote the clonal growth of hematopoietic cells in culture and
antagonize the negative regulatory effects of transforming growth
factor Despite the broad pattern of expression and ability of FGFs to activate
several FGFRs, the ability of FGF1 or FGF2 to do so in vivo may be
limited due to the multiple levels of control We now report our generation and characterization of mice lacking FGF1
and the use of these mice, in combination with our previously described
FGF2 Generation and analysis of FGF1 and FGF1-FGF2 knockout
animals.
To generate FGF1-deficient mice, a clone containing
FGF1's first exon was isolated from a 129SVJ mouse genomic library
(Stratagene). The library was screened with the human FGF1 cDNA
followed by a 120-bp NcoI-BamHI fragment
containing the first exon. Two independent clones spanning
approximately 12 kb were isolated. The targeting plasmid was
constructed by use of the pPNT replacement vector. The XhoI
and EcoRI sites of pPNT were digested, blunted, and used to
insert the 2.8-kb BamHI-EcoRI 5' arm and the
2.4-kb XbaI-NotI 3' arm, respectively. Upon
homologous recombination, a deletion of approximately 4.7 kb that
includes the entire first exon results. The plasmid was linearized with
NotI and purified, and 30 µg was electroporated into E14
embryonic stem (ES) cells. Transfected cells were selected in G418 (400 µg/ml) and FIAU
[1-(2'-deoxy-2'-fluoro-1-
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Compensation by Fibroblast Growth Factor 1 (FGF1) Does Not
Account for the Mild Phenotypic Defects Observed in FGF2 Null
Mice
ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
/ mice and in FGF1-FGF2 double-knockout mice novel
impairments in hematopoiesis that were similar in severity. Essentially
no abnormalities were found in mice lacking only FGF1. Our results suggest that the relatively mild defects in FGF2 knockout animals are
not a consequence of compensation by FGF1 and suggest highly restricted
roles for both factors under normal developmental and physiological conditions.
INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
(18). Addition of FGF to human long-term bone marrow cultures (LTBMCs) increases both the cell density of the stromal
layer and the number of hematopoietic colony-forming cells in the
cultures in a dose-dependent manner (36). The primary effects appear to be on the stromal cells in these cultures, but a
direct effect on hematopoietic progenitors cannot be ruled out.
transcriptional, translational, and secretoryover their bioavailability. In vitro studies attributing potential biological activities to either of these
FGFs must therefore be interpreted with some degree of caution. The
generation of mice with homozygous deletions of specific genes has
become a valuable tool in the evaluation of gene function in vivo,
highlighting new roles of individual genes while revealing complex
interactions among members of gene families. Several groups, including
our own, have previously reported the generation and characterization
of mice lacking FGF2 (14, 34, 42). Three independently
derived lines of FGF2 null mice are all viable and fertile. The brains
of FGF2-deficient mice contain subtle but significant reductions in the
number and organization of neurons within the cortex (14, 34,
39). FGF2 null mice show various vascular defects and are
hypotensive, although they retain the capacity to regulate blood
pressure in response to stimuli (14, 42). A delay in the
healing of full-thickness epithelial wounds in FGF2 null mice is also
observed (34). The relatively mild phenotypic defects
observed in FGF2 null mice have led to the hypothesis that FGF1 and
FGF2 may constitute a redundant pair of FGFs with similar physiological
targets and largely overlapping functions, in which case the continued
expression of FGF1 would act largely to compensate for the absence of FGF2.
/ mice, to produce FGF1/
FGF2/ double knockouts. FGF1 null animals, like
the FGF2 knockouts, are viable and fertile. Studies similar to
those we have previously described reveal that FGF1/
mice do not exhibit any of the phenotypic abnormalities associated with
deletion of FGF2; they exhibit normal brain structure and normal rates
of wound healing. In a series of new studies, we observed novel
hematopoietic deficiencies in the FGF2/ mice, while
FGF1/ mice were normal. Surprisingly, deletion of FGF1
in animals already lacking FGF2 did not seem to significantly worsen
the phenotypic defects seen in the FGF2 knockouts. This observation
suggests either that there is an extensive degree of redundancy and
compensation within the FGF family or that FGF1 and FGF2 play rather
limited roles under normal physiological conditions.
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
-D-arabinofuranosyl)-5-iodouracil] (0.25 µM) as previously described (34). Clones were
screened by Southern analysis prior to injection into C57Bl/6 blastocysts.
Brain analysis. Brain histological and immunohistochemical analyses were carried out as previously described (34), except that Nissl staining was carried out with thionine blue instead of cresyl violet.
Wound healing. Age- and sex-matched adult mice, approximately 3 to 4 months old, were anesthetized and prepared for surgery as previously described (34). Two 6-mm-diameter full-thickness epidermal wounds were created by excision with sterile scissors. After recovery, animals were examined regularly and healing was measured semiquantitatively on a 5-point scale, with 4 indicating that the original scab was present and intact, 3 meaning that the original scab was gone but a smaller scab was present, 2 representing the lack of a scab but the presence of a wound, 1 indicating that a small wound was detectable, and 0 representing a wound completely healed. All manipulations were carried out by investigators blinded to the specimens' identities.
Blood and hematopoietic analysis. Whole blood was obtained from anaesthetized mice via the retro-orbital venous sinus. White blood cells, red blood cells, and platelets were counted by using a model Zf Coulter Counter. The platelet counts were performed on platelet-rich plasma. Colony-forming cells (CFU-c) were assayed by culture in Iscove's modified Dulbecco medium made semisolid by the addition of methylcellulose in the presence of appropriate growth factors (StemCell Technologies, Vancouver, BC, Canada). The cultures were incubated under conditions that allow identification of burst-forming units-erythroid (BFU-e), colony-forming units-granulocyte (CFU-G), CFU-granulocyte/monocyte (CFU-GM), and CFU-granulocyte/erythroid/monocyte/megakaryocyte (CFU-GEMM) in the same dish. Three or four replicated cultures were scored after 7 to 8 days of incubation and again at 2 weeks. LTBMCs were prepared from femoral marrow as described elsewhere (13). Cultures were sampled biweekly to quantify the total number of cells and assess the number of hematopoietic progenitors present in the cultures. After 4 weeks, some cultures were irradiated (120 Gy) to suppress hematopoiesis and then recharged with stromally depleted low-density bone marrow cultures (BMCs). The stromally depleted BMCs were prepared by incubating low-density BMCs overnight in 100-mm-diameter dishes and discarding adherent cells. The nonadherent cells were added to the preformed, irradiated stromal layers. These cultures were then maintained and sampled for CFU-c as described above.
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RESULTS |
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Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
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Generation of mice lacking FGF1.
FGF1 is a single-copy
gene located on murine chromosome 18 and is organized into three
relatively short coding exons separated by large introns spanning
approximately 30 kb (26). Unlike the FGF2 gene,
which gives rise to multiple protein isoforms through the use of
alternative upstream translation initiation codons, the FGF1
gene is preceded by an in-frame stop codon and encodes a single
polypeptide (3). We designed a replacement vector to delete
the entire first coding exon along with several kilobases of
surrounding genomic DNA. The deleted sequences were replaced with
a neomycin resistance cassette (neor) driven by
the mouse phosphoglycerate kinase (PGK) promoter and containing the PGK
polyadenylation signal. The vector also contained a herpes simplex
virus thymidine kinase (hsv-TK) gene, allowing recombinants
to be screened by both positive and negative selection (Fig.
1A).
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) is
detected by using an external probe. A normal clone (+/+) is shown for
comparison. (Center and bottom) Litters from crosses of heterozygous
mice contain wild-type (+/+), heterozygous (+/ genotype. We then intercrossed these
heterozygous animals to generate FGF1 null animals (Fig. 1B, middle and
lower panels).
We confirmed the absence of FGF1 protein in the FGF1 null animals
through Western analysis of various tissues. Analysis of whole-cell
extracts (Fig. 1C, top) from brain (lanes 2 to 4) and heart (lanes 5 to
7) tissues showed the presence of FGF1 protein in FGF1+/+
(lanes 2 and 5) and FGF1+/ (lanes 3 and 6) animals but
not in FGF1/ animals (lanes 4 and 7). We also analyzed
heparin-Sepharose concentrates of whole-cell extracts (Fig. 1C,
center). While FGF1 protein is easily detected in 40 µg of whole-cell
extract from wild-type and heterozygous mice (top panel), it remains
undetectable in 5 mg of concentrated protein from FGF1 null mice
(center panel, lanes 4 and 7). As expected, FGF2 is readily detected in
heparin-Sepharose concentrates from animals of all three FGF1 genotypes
(bottom panel). We performed a similar analysis on a range of tissues, including skull, long bone, liver, spleen, lung, skeletal muscle, kidney, testis, and eye, and could not detect FGF1 protein in any
tissues from FGF1/ animals. We also did not observe an
increase in FGF2 expression in any tissues derived from
FGF1/ animals compared to FGF1+/+ and
FGF+/ mice, suggesting that FGF2 expression is not
upregulated in the absence of FGF1 (data not shown).
Crosses of FGF1 heterozygotes revealed that wild-type, heterozygotes,
and FGF1 null animals were born at the expected frequencies. The
FGF1/ mice appeared indistinguishable from their
wild-type littermates and grew, developed, and bred normally. No
significant differences were seen in the size or weight of the
homozygous mutants compared to their wild-type littermates.
Histopathological examination of a range of tissues from
FGF1/ animals did not reveal any striking defects,
consistent with the macroscopically normal appearance and behavior of
the animals. We also have not observed any disorders in elderly FGF1
null animals, suggesting that there are no long-term disorders that are
degenerative in nature.
Generation of FGF1-FGF2 double-knockout animals. One explanation for the absence of any obvious phenotypic defects in the FGF1 knockouts is the continued expression of FGF2. Similarly, the presence of only relatively minor phenotypic defects in the FGF2 knockouts could be due to the continued expression of FGF1. We therefore hypothesized that animals lacking both FGF1 and FGF2 would exhibit more severe phenotypic abnormalities than either line of single-knockout mice or would display novel defects not present in either single-knockout line. We intercrossed our FGF1 and FGF2 single-knockout mice to generate mice lacking both FGF1 and FGF2.
Crosses of FGF1/ and FGF2/ mice
produced litters of normal size that contained exclusively
FGF1+/ FGF2+/ mice, as expected. We used
these double heterozygotes to generate animals lacking FGF1
and FGF2 alleles in various combinations, including animals
with only a single functional allele (FGF1+/
FGF2/ or FGF1/
FGF2+/) and animals null for both FGF genes
(FGF1/ FGF2/).
All animals were born at the expected frequencies. Animals of all
genotypes were grossly normal and developed and bred normally.
The absence of FGF1 and FGF2 expression in the double knockouts was
confirmed by Western analysis of extracts from brains of wild-type,
FGF1/ single-knockout, FGF2/
single-knockout, and FGF1/ FGF2/
double-knockout animals (Fig. 1D). For detection of FGF1, whole-cell extracts were directly loaded onto a polyacrylamide gel (left); for
FGF2, proteins were first concentrated by the use of heparin-Sepharose beads (right). We readily detected FGF1 protein in wild-type and FGF2/ animals and FGF2 expression in wild-type and
FGF1/ animals but could not detect expression of either
FGF1 or FGF2 in double-knockout animals, confirming the absence of both
proteins in these mice.
Brain analysis.
Both FGF1 and FGF2 are highly expressed in
adult brain tissue. Although the brains of all lines of our FGF
knockout mice are macroscopically indistinguishable from their
wild-type counterparts, we have previously observed microscopic
differences in neuronal structure in brains of FGF2/
mice. We noted abnormalities in the cytoarchitecture of the neocortex which were most pronounced in the frontal sensorimotor area
(34). Others have also reported brain abnormalities in
animals lacking FGF2 (14), including decreases in numbers
both neurons and glial cells (39). Because FGF1 and FGF2
have similar temporal and spatial expression patterns within the brain
(15), we undertook a series of studies, similar to those
previously done with the FGF2 null animals, to determine whether
deletion of FGF1 resulted in comparable neuronal defects.
/ mice, a combination of
Nissl staining and immunohistochemical analysis revealed a thickening of the neocortex and a coincident decrease in neuronal cell density. A
similar analysis of the brains of FGF1/ mice was
therefore performed. A comparison of matched coronal sections
throughout the brains of age- and sex-matched wild-type and
FGF1/ animals did not reveal any significant
differences in the architecture of the cortex or in the number of
neurons present. Nissl-stained sections from FGF1/
animals were indistinguishable from those of wild-type animals (Fig. 2A
and B). We next compared brains of
FGF1/ FGF2/ mice with those of the FGF2
single knockouts to determine whether additional deletion of FGF1 in
these animals resulted in more-severe defects. While we observed a
thickening of the neocortex in double-knockout mice compared to
wild-type animals, we did not detect more extensive changes than those
seen in FGF2/ mice (Fig. 2C and D).
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/ animals (Fig. 2E, F, I, and J). Analysis of brain
tissue from FGF2/ and FGF1-FGF2 double-knockout mice
revealed the same phenotype as that observed with Nissl staining; while
clear differences between the brains of double-knockout and wild-type
mice were noted, no significant differences between FGF2 single- and
FGF1-FGF2 double-knockout animals could be detected (Fig. 2G, H, K, and L). We cannot, however, rule out the possibility that future studies, investigating other regions of the brain or neuronal subpopulations, will reveal differences between these groups of mice that have not been
detected here.
Wound healing.
We have previously described a small but
reproducible delay in the healing of full-thickness excisional wounds
in FGF2/ animals. Preliminary studies with our
FGF1/ mice indicated that deletion of FGF1 had no
effect on the rate of healing of such wounds (data not shown). We were
interested in determining whether FGF1-FGF2 double-knockout animals had
a wound healing delay longer that that seen in FGF2 single knockouts.
/, FGF2/, and FGF1/
FGF2/) were used to determine rates of wound healing
and allow direct comparison of all groups with one another. Two
6-mm-diameter full-thickness excisional wounds were created on the back
of each mouse, and the degree of wound healing was assessed visually,
using a semiquantitative scale (described in Materials and Methods). At
the time of wounding and throughout the experiment, all procedures and
wound evaluations were performed in a genotype-blinded manner. At the
end of the experiment, the data were analyzed and plotted as both
percentage of animals completely healed versus time (as in the previous
study) and mean degree of healing (wound score) versus time.
The wild-type and FGF1/ animals exhibited the same
degree of wound healing (Fig. 3A). The
rate of wound healing in FGF2/ mice was delayed.
FGF1/ FGF2/ mice displayed a delay in
wound healing similar to that seen in the FGF2 single knockouts. While
there was a small difference in wound healing of FGF2/
and double knockouts at days 15 and 21, it is clear that deletion of
both FGF1 and FGF2 did not result in large-scale defects in wound
healing. Similar results were obtained when the data were plotted as
the percentages of animals in which both wounds were completely healed
in the groups (Fig. 3B). Wild-type and FGF1 null animals exhibited
similar rates of wound healing, and the rates of healing in
FGF2/ and FGF1-FGF2 double-knockout mice, while slower
than that of the other two groups, were similar to one another. While
these results do not rule out the possibility of a role for FGF1 in wound healing, any contribution it makes would seem to be smaller than
that of FGF2 and beyond the limits of detection in this experiment. Additionally, any differences in rate of wound healing between FGF2/ and double-knockout mice must also be very small.
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Hematopoiesis.
No significant differences were detected in the
white blood cell, red blood cell, or platelet counts of
FGF1/, FGF2/, and FGF1/
FGF2/ mice compared to wild-type animals. The
differential counts for all of these mice were also within the normal
range. Femoral bone marrow was obtained from each group of mice and
cultured in semisolid medium to determine the number of steady-state
hematopoietic progenitors present. Again, no differences in colony
formation were observed between control BMCs and those from FGF
knockout mice (data not shown).
/, and FGF2/ mice. Stromal cells
from all mice became confluent after 3 weeks in culture. At weekly
intervals the nonadherent layer was sampled for myeloid progenitors and
CFU-c were quantified. No statistically significant differences between
cultures derived from wild-type and FGF1/ mice were
detected. On the other hand, at all time points, cultures obtained from
FGF2/ mice had fewer colonies than either wild-type or
FGF1/-derived cultures (Fig.
4A). We also examined CFU-c in mice
lacking both FGF1 and FGF2. LTBMCs were readily established, and the
stromal cells grew as well as those from age-matched wild-type
controls. After 4 weeks, the cultures prepared from the FGF1-FGF2
double-knockout animals showed a degree of hematopoietic impairment
similar to that of the FGF2/-derived cultures (Fig.
4B).
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/ FGF2/ mice. After the cultures
were established, they were irradiated to suppress endogenous
hematopoiesis. Cultures were subsequently recharged with fresh BMC from
either wild-type or FGF1-FGF2 double-knockout mice and incubated for an
additional 5 weeks. Wild-type stroma restored CFU-c production by both
wild-type and double-knockout BMC, and FGF-deficient stroma was unable
to restore CFU-c production by either wild-type or double-knockout BMC
(Fig. 4C). This result strongly suggests that the impaired
hematopoiesis in cultures derived from FGF1/
FGF2/ animals arises primarily from a defect in the
stromal layer and is not a consequence of a defect in the hematopoietic progenitors.
We have also examined LTBMCs prepared from FGF1-FGF2 double-knockout
animals ranging in age from 3 weeks to 1 year. No sign of an
age-related deterioration in the capacity to support hematopoiesis in
comparison to wild type mice has been seen (data not shown).
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DISCUSSION |
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Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
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We and others have previously described a range of phenotypic defects in mice lacking FGF2, including changes in the number of neurons present in the cerebral cortex, a delay in the healing of epithelial wounds, and defects in the regulation of blood pressure (14, 34, 39, 42). While these physical and physiological consequences of FGF2 deletion are readily detectable, perhaps the most striking characteristic they share is the limited extent to which they impact development, growth, and homeostasis. The observation that FGF2 knockouts display some phenotypic defects indicates that this factor does play roles in certain developmental and physiological processes that cannot be performed by other proteins. However, because FGF2 is so widely expressed in so many tissues and has been found to induce such a wide range of responses from various cell types in vitro, the rather mild phenotypic abnormalities accompanying its deletion were somewhat surprising.
The failure of FGF2 deletion to result in widespread and extensive negative consequences might be minimized due to the continued expression of other factors, including other FGF family members. Of all the FGFs, the one that exhibits the most similarity to FGF2 in terms of structure, expression pattern, and cellular and subcellular localization is FGF1. The fact that FGF1 is capable of binding and activating all known FGFR splice variants suggests that this molecule might be able to act as a substitute for FGF2 in the knockout mice, effectively replacing FGF2 function through binding to the same receptors and eliciting similar biological responses. To address this possibility, we generated FGF1 null mice. While mice lacking FGF1 are worthy of study in their own right, we were especially interested in determining the consequences of deletion of both FGF1 and FGF2 in the same animal.
Using techniques similar to those previously employed to establish differences in brain structure and wound healing between wild-type and FGF2 knockout mice, we were unable to detect any differences between wild-type and FGF1 knockout mice. We did not observe significant differences between wild-type and FGF1 null mice in in vitro hematopoiesis, although we readily detected such differences between wild-type and FGF2 null mice. These observations suggest that any differences between FGF1 knockout mice and control animals must be smaller than those between FGF2 knockout mice and controls. However, the possibility of compensation for loss of FGF1 by FGF2 in these mice remained. We were therefore interested in determining the impact of deleting both FGF1 and FGF2. If our compensation hypothesis were correct, then we would expect deletion of FGF1 in animals already lacking FGF2 to result in a host of novel phenotypic abnormalities as well as to significantly worsen the previously observed defects.
Our analysis of FGF1-FGF2 double-knockout mice suggests that compensation does not explain the relatively mild phenotypic defects associated with deletion of either single factor, insofar as the double-knockout mice do not exhibit significantly worse defects than mice lacking only FGF2. This result demonstrates that the failure of FGF1 knockout mice to display any detectable phenotype is unlikely to be due to the continued expression of FGF2 and that the relatively mild phenotypic defects seen in the FGF2 knockout are probably not a consequence of the continued expression of FGF1.
There are several explanations for our failure to detect significant
differences between wild-type and FGF1/ mice and
between FGF2/ and FGF1/
FGF2/ mice. First, it is possible that we did not
detect phenotypic differences arising from FGF1 deletion simply because
there are none that can be seen under normal circumstances. Although we were able to rule out compensation by FGF1 or FGF2 in each of the
single knockouts through generation of the double knockout, it could be
that other FGFs are compensating for the absence of both FGF1 and FGF2.
It need not necessarily be an FGF that is providing the compensatory
signal, since other molecules may act to functionally replace the
missing growth factors. If this is the case, it suggests a remarkable
degree of redundancy among various FGF family members or between
multiple growth factor signaling pathways.
An alternate, related explanation is that FGF1 and FGF2 play a very
limited role in normal physiological processes, although they
presumably perform some functions in specific situations, such as
following stress or injury. In this scenario, the roles of FGF1 and
FGF2 are limited during development and normal adult life. In specific
situations, however, these factors play crucial roles. Support for this
interpretation comes from our study of wound healing: the developmental
pathways leading to the formation of skin appear normal in wild-type
and knockout animals, but after wounding, repair takes longer in the
FGF2/ and FGF1-FGF2 knockout mice than in the wild
type. If this explanation is valid, then only by studying the mice in
the appropriate pathological state will differences between wild-type
and knockout mice become apparent.
It is also possible that we failed to detect consequences of FGF1
deletion because such defects are present but not very large. Deletion
of FGF1 could produce phenotypic effects below the threshold of
detection by the methods employed in this report. Because we have used
similar techniques to document significant differences between
wild-type and FGF2/ mice, the theoretical differences
between wild-type and FGF1/ mice, as well as between
FGF2/ and double-knockout mice, must be smaller than
those between wild-type and FGF2/ mice. The possibility
of significant, but smaller, defects arising from FGF1 deletion
nevertheless remains.
Finally, a more trivial explanation, but one that cannot be ignored, is that differences due to the absence of FGF1 and FGF2 are present and detectable, but not in the tissues we studied. If this were the case, then we would anticipate that analysis of other organ systems or additional physiological processes might yield differences that we have thus far been unable to detect. We believe that future studies, particularly those utilizing cultured cells derived from these animals, may reveal roles for FGF1 and FGF2 that are real, even if they are partially redundant with roles of other growth factors. For example, we have found that osteoblasts derived from FGF1-FGF2 null mice undergo premature differentiation in culture (unpublished results). This is in line with the finding that FGF signaling inhibits osteoblast differentiation (10) and suggests that FGF2 (and possibly FGF1) production by osteoblasts plays a role in regulating this process. Similarly, although FGF1-FGF2 null mice exhibit no significant hematopoietic defects, the maturation and differentiation of their hematopoietic stem cells in culture are impaired. Thus, we believe that these mice and their tissues will be useful in the assessment of the role of FGF1 and FGF2 signaling in a variety of physiological and pathological processes.
What is clear from the results obtained so far, however, is that FGF1 and FGF2 do not seem to play critical roles in development and homeostasis. Animals lacking either or both factors develop and breed normally and are largely identical to their wild-type counterparts. Important roles for FGF1 and FGF2 in a wide range of biological processes have been postulated based on a wealth of experimental evidence, including cell culture studies in vitro and transgenic approaches in vivo. While these studies have identified broad potential activities for these factors, our data suggest rather limited roles for FGF1 and FGF2 which may only be apparent under very specific conditions.
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ACKNOWLEDGMENTS |
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We thank Michael Ittmann and Magdalena Sastre for helpful discussions and Earl Nonon for help in the wound healing experiments, as well as the personnel of the NYU Medical Center Transgenic/ES Cell Chimera Facility.
This investigation was supported by Public Health Service grant CA42568 from the National Cancer Institute.
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FOOTNOTES |
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* Corresponding author. Mailing address: Department of Microbiology, New York University School of Medicine, 550 First Ave., New York, NY 10016. Phone: (212) 263-5341. Fax: (212) 263-8714. E-mail: BasilC01{at}mcrcr.med.nyu.edu.
Present address: Centro Nacional de Biotecnologia, Campus
Universidad Autonoma, Madrid, Spain.
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REFERENCES |
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Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
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| 1. |
Arman, E.,
R. Haffner-Krausz,
Y. Chen,
J. K. Heath, and P. Lonai.
1998.
Targeted disruption of fibroblast growth factor (FGF) receptor 2 suggests a role for FGF signaling in pregastrulation mammalian development.
Proc. Natl. Acad. Sci. USA
95:5082-5087 |
| 2. |
Barnea, A., and G. Cho.
1993.
Basic fibroblast growth factor selectively amplifies the functional state of neurons producing neuropeptide Y but not somatostatin in cultures of fetal brain cells: evidence for a cooperative interaction with insulin-like growth factor-I.
Endocrinology
133:1895-1898 |
| 3. | Basilico, C., and D. Moscatelli. 1992. The FGF family of growth factors and oncogenes. Adv. Cancer Res. 59:115-165[Medline]. |
| 4. | Bennett, N. T., and G. S. Schultz. 1993. Growth factors and wound healing: biochemical properties of growth factors and their receptors. Am. J. Surg. 165:728-737[CrossRef][Medline]. |
| 5. | Bennett, N. T., and G. S. Schultz. 1993. Growth factors and wound healing. II. Roles in normal and chronic wound healing. Am. J. Surg. 166:74-81[CrossRef][Medline]. |
| 6. |
Bikfalvi, A.,
S. Klein,
G. Pintucci, and D. B. Rifkin.
1997.
Biological roles of fibroblast growth factor-2.
Endocr. Rev.
18:26-45 |
| 7. |
Bugler, B.,
F. Amalric, and H. Prats.
1991.
Alternative initiation of translation determines cytoplasmic or nuclear localization of basic fibroblast growth factor.
Mol. Cell. Biol.
11:573-577 |
| 8. | Burgess, W. H., and T. Maciag. 1989. The heparin-binding (fibroblast) growth factor family of proteins. Annu. Rev. Biochem. 58:575-606[CrossRef][Medline]. |
| 9. | Colvin, J. S., B. A. Bohne, G. W. Harding, D. G. McEwen, and D. M. Ornitz. 1996. Skeletal overgrowth and deafness in mice lacking fibroblast growth factor receptor 3. Nat. Genet. 12:390-397[CrossRef][Medline]. |
| 10. | Debiais, F., M. Hott, A. M. Graulet, and P. J. Marie. 1998. The effects of fibroblast growth factor-2 on human neonatal calvaria osteoblastic cells are differentiation stage specific. J. Bone Miner. Res. 13:645-654[CrossRef][Medline]. |
| 11. | Deng, C., A. Wynshaw-Boris, F. Zhou, A. Kuo, and P. Leder. 1996. Fibroblast growth factor receptor 3 is a negative regulator of bone growth. Cell 84:911-921[CrossRef][Medline]. |
| 12. |
Deng, C. X.,
A. Wynshaw-Boris,
M. M. Shen,
C. Daugherty,
D. M. Ornitz, and P. Leder.
1994.
Murine FGFR-1 is required for early postimplantation growth and axial organization.
Genes Dev.
8:3045-3057 |
| 13. | Dexter, T. M., and N. G. Testa. 1980. In vitro methods in haemopoiesis and lymphopoiesis. J. Immunol. Methods 38:177-190[CrossRef][Medline]. |
| 14. | Dono, R., G. Texido, R. Dussel, H. Ehmke, and R. Zeller. 1998. Impaired cerebral cortex development and blood pressure regulation in FGF-2-deficient mice. EMBO J. 17:4213-4225[CrossRef][Medline]. |
| 15. | Eckenstein, F. P. 1994. Fibroblast growth factors in the nervous system. J. Neurobiol. 25:1467-1480[CrossRef][Medline]. |
| 16. |
Feldman, B.,
W. Poueymirou,
V. E. Papaioannou,
T. M. DeChiara, and M. Goldfarb.
1995.
Requirement of FGF-4 for postimplantation mouse development.
Science
267:246-249 |
| 17. |
Floss, T.,
H. H. Arnold, and T. Braun.
1997.
A role for FGF-6 in skeletal muscle regeneration.
Genes Dev.
11:2040-2051 |
| 18. |
Gabrilove, J. L.,
G. Wong,
E. Bollenbacher,
K. White,
S. Kojima, and E. L. Wilson.
1993.
Basic fibroblast growth factor counteracts the suppressive effect of transforming growth factor-1 on human myeloid progenitor cells.
Blood
81:909-915 |
| 19. | Galzie, Z., A. R. Kinsella, and J. A. Smith. 1997. Fibroblast growth factors and their receptors. Biochem. Cell Biol. 75:669-685[CrossRef][Medline]. |
| 20. | Ghosh, A., and M. E. Greenberg. 1995. Distinct roles for bFGF and NT-3 in the regulation of cortical neurogenesis. Neuron 15:89-103[CrossRef][Medline]. |
| 21. | Goldfarb, M. 1996. Functions of fibroblast growth factors in vertebrate development. Cytokine Growth Factor Rev. 7:311-325[CrossRef][Medline]. |
| 22. |
Guo, L.,
L. Degenstein, and E. Fuchs.
1996.
Keratinocyte growth factor is required for hair development but not for wound healing.
Genes Dev.
10:165-175 |
| 23. | Hebert, J. M., T. Rosenquist, J. Gotz, and G. R. Martin. 1994. FGF5 as a regulator of the hair growth cycle: evidence from targeted and spontaneous mutations. Cell 78:1017-1025[CrossRef][Medline]. |
| 24. |
Imamura, T.,
K. Engleka,
X. Zhan,
Y. Tokita,
R. Forough,
D. Roeder,
A. Jackson,
J. A. M. Maier,
T. Hla, and T. Maciag.
1990.
Recovery of mitogenic activity of a growth factor mutant with a nuclear translocation sequence.
Science
249:1567-1570 |
| 25. | Kniss, D. A., and R. W. Burry. 1988. Serum and fibroblast growth factor stimulate quiescent astrocytes to re-enter the cell cycle. Brain Res. 439:281-288[CrossRef][Medline]. |
| 26. | Madia, F., K. V. Hackshaw, and I.-M. Chiu. 1996. Cloning and characterization of the mouse Fgf-1 gene. Gene 179:231-236[CrossRef][Medline]. |
| 27. |
Mansour, S. L.,
J. M. Goddard, and M. R. Capecchi.
1993.
Mice homozygous for a targeted disruption of the proto-oncogene int-2 have developmental defects in the tail and inner ear.
Development
117:13-28 |
| 28. | Matsuda, S., H. Saito, and N. Nishiyama. 1990. Effect of basic fibroblast growth factor on neurons cultured from various regions of postnatal rat brain. Brain Res. 520:310-316[CrossRef][Medline]. |
| 29. | Mellin, T. N., D. E. Cashen, J. J. Ronan, B. S. Murphy, J. DiSalvo, and K. A. Thomas. 1995. Acidic fibroblast growth factor accelerates dermal wound healing in diabetic mice. Investig. Dermatol. 104:850-855[CrossRef][Medline]. |
| 30. | Meyers, E. N., M. Lewandoski, and G. R. Martin. 1998. An Fgf8 mutant allelic series generated by Cre- and Flp-mediated recombination. Nat. Genet. 18:136-141[CrossRef][Medline]. |
| 31. |
Min, H.,
D. M. Danilenko,
S. A. Scully,
B. Bolon,
B. D. Ring,
J. E. Tarpley,
M. DeRose, and W. S. Simonet.
1998.
Fgf-10 is required for both limb and lung development and exhibits striking functional similarity to Drosophila branchless.
Genes Dev.
12:3156-3161 |
| 32. | Okumura, M., T. Okuda, T. Nakamura, and M. Yajima. 1996. Acceleration of wound healing in diabetic mice by basic fibroblast growth factor. Biol. Pharm. Bull. 19:530-535[Medline]. |
| 33. |
Ornitz, D. M.,
J. Xu,
J. S. Colvin,
D. G. McEwen,
C. A. MacArthur,
F. Coulier,
G. Gao, and M. Goldfarb.
1996.
Receptor specificity of the fibroblast growth factor family.
J. Biol. Chem.
271:15292-15297 |
| 34. |
Ortega, S.,
M. Ittmann,
S. H. Tsang,
M. Ehrlich, and C. Basilico.
1998.
Neuronal defects and delayed wound healing in mice lacking fibroblast growth factor 2.
Proc. Natl. Acad. Sci. USA
95:5672-5677 |
| 35. | Qian, X., A. A. Davis, S. K. Goderie, and S. Temple. 1997. FGF2 concentration regulates the generation of neurons and glia from multipotent cortical stem cells. Neuron 18:81-93[CrossRef][Medline]. |
| 36. |
Quito, F. L.,
J. Beh,
O. Bashayan,
C. Basilico, and R. S. Basch.
1996.
Effects of fibroblast growth factor-4 (k-FGF) on long-term cultures of human bone marrow cells.
Blood
87:1282-1291 |
| 37. |
Smallwood, P. M.,
I. Munoz-Sanjuan,
P. Tong,
J. P. Macke,
S. H. Hendry,
D. J. Gilbert,
N. G. Copeland,
N. A. Jenkins, and J. Nathans.
1996.
Fibroblast growth factor (FGF) homologous factors: new members of the FGF family implicated in nervous system development.
Proc. Natl. Acad. Sci. USA
93:9850-9857 |
| 38. | Temple, S., and Qian. 1995. bFGF, neurotrophins, and the control or cortical neurogenesis. Neuron 15:249-252[CrossRef][Medline]. |
| 39. | Vaccarino, F. M., M. L. Schwartz, R. Raballo, J. Nilsen, J. Rhee, M. Zhou, T. Doetschman, J. D. Coffin, J. J. Wyland, and Y. T. Hung. 1999. Changes in cerebral cortex size are governed by fibroblast growth factor during embryogeneisis. Nat. Neurosci. 2:246-253[CrossRef][Medline]. |
| 40. | Xu, X., M. Weinstein, C. Li, M. Naski, R. I. Cohen, R. M. Ornitz, P. Leder, and C. Deng. 1998. Fibroblast growth factor receptor 2 (FGFR2)-mediated reciprocal regulation loop between FGF8 and FGF10 is essential for limb induction. Development 125:753-765[Abstract]. |
| 41. |
Yamaguchi, T. P.,
K. Harpal,
M. Henkemeyer, and J. Rossant.
1994.
fgfr-1 is required for embryonic growth and mesodermal patterning during mouse gastrulation.
Genes Dev.
8:3032-3044 |
| 42. | Zhou, M., R. L. Sutliff, R. J. Paul, J. N. Lorenz, J. B. Hoying, C. C. Haudenschild, M. Yin, J. D. Coffin, L. Kong, E. G. Kranias, W. Luo, G. P. Boivin, J. J. Duffy, S. A. Pawlowski, and T. Doetschman. 1998. Fibroblast growth factor 2 control of vascular tone. Nat. Med. 4:201-207[CrossRef][Medline]. |
Molecular and Cellular Biology, March 2000, p. 2260-2268, Vol. 20, No. 6
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Copyright © 2000, American Society for Microbiology. All rights reserved.
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