An alternatively spliced fibroblast growth factor (FGF)-5 mRNA is abundant in brain and translates into a partial agonist/antagonist for FGF-5 neurotrophic activity

Gender-Difference in Hair Length as Revealed by Crispr-Based Production of Long-Haired Mice with Dysfunctional FGF5 Mutations

Fibroblast growth factor 5 (FGF5) is an important molecule required for the transition from anagen to catagen phase of the mammalian hair cycle. We previously reported that Syrian hamsters harboring a 1-bp deletion in the Fgf5 gene exhibit excessive hair growth in males. Herein, we generated Fgf5 mutant mice using genome editing via oviductal nucleic acid delivery (GONAD)/improved GONAD (i-GONAD), an in vivo genome editing system used to target early embryos present in the oviductal lumen, to study gender differences in hair length in mutant mice. The two lines (Fgf5go-malc), one with a 2-bp deletion (c.552_553del) and the other with a 1-bp insertion (c.552_553insA) in exon 3 of Fgf5, were successfully established. Each mutation was predicted to disrupt a part of the FGF domain through frameshift mutation (p.Glu184ValfsX128 or p.Glu184ArgfsX128). Fgf5go-malc1 mice had heterogeneously distributed longer hairs than wild-type mice (C57BL/6J). Notably, this change was more evident in males than in females (p < 0.0001). Immunohistochemical analysis revealed the presence of FGF5 protein in the dermal papilla and outer root sheath of the hair follicles from C57BL/6J and Fgf5go-malc1 mice. Histological analysis revealed that the prolonged anagen phase might be the cause of accelerated hair growth in Fgf5go-malc1 mice.

Functional Roles of FGF Signaling in Early Development of Vertebrate Embryos

Fibroblast growth factors (FGFs) comprise a large family of growth factors, regulating diverse biological processes including cell proliferation, migration, and differentiation. Each FGF binds to a set of FGF receptors to initiate certain intracellular signaling molecules. Accumulated evidence suggests that in early development and adult state of vertebrates, FGFs also play exclusive and context dependent roles. Although FGFs have been the focus of research for therapeutic approaches in cancer, cardiovascular disease, and metabolic syndrome, in this review, we mainly focused on their role in germ layer specification and axis patterning during early vertebrate embryogenesis. We discussed the functional roles of FGFs and their interacting partners as part of the gene regulatory network for germ layer specification, dorsal-ventral (DV), and anterior-posterior (AP) patterning. Finally, we briefly reviewed the regulatory molecules and pharmacological agents discovered that may allow modulation of FGF signaling in research.

Effect of cysteine-free human fibroblast growth factor-5s mutant (FGF5sC93S) on hair growth

Treatment for hair loss is largely limited, and any beneficial effects are often transient. Based on the critical role of the FGF5 isoform, FGF5s, in the hair growth cycle, it may be a good therapeutic candidate for the prevention of hair loss, as well as the promotion of hair growth. To investigate its potential use for hair growth, a mutant form of the FGF5s protein (FGF5sC93S) was generated, expressed, and purified. The FGF5sC93S mutant was able to antagonize FGF5-induced mitogenic activity, which normally triggers the conversion of hair follicles from the anagen phase to the catagen phase. In addition, the FGF5sC93S mutant efficiently suppressed gene expression induced by FGF5 both human outer root sheath (hORS) and human dermal papilla (hDP) cells. Administration of FGF5sC93S proteins onto the scalps of human subjects significantly increased the total number of hairs at 24 weeks. Together, our data demonstrate that a mutant form of the FGF5s protein could be used as a potential hair promoting agent.

Insights into the Evolution of Neoteny from the Genome of the Asian Icefish Protosalanx chinensis

Salangids, known as Asian icefishes, represent a peculiar radiation within the bony fish order Protacanthopterygii where adult fish retain larval characteristics such as transparent and miniaturized bodies and a cartilaginous endoskeleton into adulthood. Here, we report a de novo genome of Protosalanx chinensis, the most widely distributed salangid lineage. The P. chinensis genome assembly is more contiguous and complete than a previous assembly. We estimate that P. chinensis, salmons, trouts, and pikes diverged from a common ancestor 185 million years ago. A juxtaposition with other fish genomes revealed loss of the genes encoding ectodysplasin-A receptor (EDAR), SCPP1, and four Hox proteins and likely lack of canonical fibroblast growth factor 5 (FGF5) function. We also report genomic variations of P. chinensis possibly reflecting the immune system repertoire of a species with a larval phenotype in sexually mature individuals. The new Asian icefish reference genome provides a solid foundation for future studies.

FGF5 methylation is a sensitivity marker of esophageal squamous cell carcinoma to definitive chemoradiotherapy

Definitive chemoradiotherapy (dCRT) is the major treatment for esophageal squamous cell carcinoma (ESCC), and prediction of the response to dCRT is important so as not to miss an opportunity to cure an ESCC. Nevertheless, few validated markers are available. Here, we aimed to identify a highly reproducible marker using multi-layer omics analysis. 117 ESCC samples from 67 responders and 50 non-responders were divided into screening, validation, and re-validation sets. In the screening cohort (n = 41), somatic mutations in 114 genes showed no association with dCRT response. Genome-wide DNA methylation analysis using Infinium HumanMethylation450 BeadChip array identified four genic regions significantly associated with dCRT response. Among them, FGF5 methylation was validated to be associated with dCRT response (n = 34; P = 0.001), and further re-validated (n = 42; P = 0.020) by bisulfite-pyrosequencing. The sensitivity and specificity in the combined validation and re-validation sets (n = 76) were 45% and 90%, respectively, by using the cut-off value established in the screening set, and FGF5 methylation had predictive power independent from clinicopathological parameters. In ESCC cell lines, FGF5 promoter methylation repressed its expression. FGF5 expression was induced by cisplatin (CDDP) treatment in three unmethylated cell lines, but not in two methylated cell lines. Exogenous FGF5 overexpression in a cell line with its methylation conferred resistance to CDDP. In non-cancerous esophageal tissues, FGF5 was not expressed, and its methylation was present in a small fraction of cells. These results showed that FGF5 methylation is a validated marker for ESCC sensitivity to dCRT.

CRISPR/Cas9-mediated loss of FGF5 function increases wool staple length in sheep

Fibroblast growth factor 5 (FGF5) regulates hair length in humans and a variety of other animals. To investigate whether FGF5 has similar effects in sheep, we used clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated 9 (Cas9) to generate loss-of-function mutations with the FGF5 gene in Chinese Merino sheep. A total of 16 lambs were identified with genetic mutations within the targeting locus: 13 lambs had biallelic modifications and three lambs had monoallelic modifications. Characterization of the modifications revealed that 13 were frameshift mutations that led to premature termination, whereas the other three were in-frame deletions. Thus, CRISPR/Cas9 efficiently generated loss-of-function mutations in the sheep FGF5 gene. We then investigated the effect of loss of FGF5 function on wool traits in 12 lambs and found that wool staple length and stretched length of genetically modified (GM) yearling sheep were significantly longer compared with that of wild-type (WT) control animals. The greasy fleece weight of GM yearling sheep was also significantly greater compared with that of WT sheep. Moreover, the mean fiber diameter in GM sheep showed no significant difference compared with WT sheep, suggesting that the increase in greasy fleece weight was likely attributed to the increase in wool length. The results of this study suggest that CRISPR/Cas9-mediated loss of FGF5 activity could promote wool growth and, consequently, increase wool length and yield.

Ectopic expression of FGF5s induces wool growth in Chinese merino sheep

Fibroblast growth factor 5 (FGF5) has been recognized as an inhibitor to cease animal hair growth, while in contrary, FGF5 short alternative transcript (FGF5s) can induce hair growth by antagonizing FGF5 function. To investigate the role of FGF5s in wool growth in Chinese Merino sheep, we generated transgenic sheep of ectopic expression of FGF5s by injection of recombinant lentivirus into zygote. Totally 20 transgenic sheep were obtained and 12 were alive after birth. Characterization of the transgene revealed that the transgenic sheep showed variety of integrant, ranged from 2 to 11 copies of transgene. The ectopic expression of FGF5s was observed in all transgenic sheep. Further study on the effect of ectopic expression of FGF5s revealed that the wool length of transgenic sheep were significantly longer than that of non-transgenic control, with 9.17cm of transgenic lambs versus 7.58cm of control animals. Notably, besides the increase of wool length, the yearling greasy fleece weight was also concordantly greater than that of wild-type (p<0.01), with 3.22kg of transgenic sheep versus 2.17kg of control lambs (p<0.01) in average. Our results suggested that overexpression of FGF5s could stimulate wool growth and resulted in increase of wool length and greasy wool weight.

Role of Fibroblast Growth Factor-5 on the Proliferation of Human Tonsil-Derived Mesenchymal Stem Cells

Human mesenchymal stem cells (MSCs) are a promising tool for therapeutic applications in cell-based therapy and regenerative medicine, and MSCs from the human palatine tonsils have recently been used as a new tissue source. However, the understanding of the proliferation and differentiation capacity of tonsil-derived MSCs (T-MSCs) is limited. In this study, we compared the proliferative potential of T-MSCs with those of bone marrow MSCs (BM-MSCs) and adipose tissue-derived MSCs (A-MSCs). Additionally, we investigated the underlying mechanism of T-MSC function. We showed that T-MSCs proliferated faster than A-MSCs and BM-MSCs in methylthiazolyl diphenyl-tetrazolium (MTT) assays, cell count assays, and cell cycle distribution analyses. DNA microarray and real-time PCR analyses revealed that the expression of fibroblast growth factor-5 (FGF5) was significantly elevated in T-MSCs compared with those in A-MSCs and BM-MSCs. Cell growth curves showed a difference in cell growth between untreated cells and siFGF5-treated T-MSCs. The administration of recombinant human FGF5 (rhFGF5) to the cells transfected with siFGF5 led to a significant increase in the proliferation rates. The administration of rhFGF5 to T-MSCs led to an increase in the levels of phosphorylated ERK1/2. However, treatment with siFGF5 resulted in an overall decrease in the level of phosphorylated ERK1/2. The osteogenic differentiation of T-MSCs was reduced following siFGF5 transfection, and it recovered to near-normal levels when rhFGF5 was added. These findings indicate that T-MSCs show significantly higher proliferative potential compared with those of BM-MSCs and A-MSCs. FGF5 facilitates cell proliferation through ERK1/2 activation, and it influences the osteogenic differentiation of T-MSCs.

Fibroblast growth factor 5-short (FGF5s) inhibits the activity of FGF5 in primary and secondary hair follicle dermal papilla cells of cashmere goats

To determine the relationship between fibroblast growth factor 5 (FGF5) and FGF5-short (FGF5s) in dermal papilla cells of cashmere goat primary and secondary hair follicles. We isolated dermal papilla cells from primary hair follicle (PHF) and secondary hair follicle (SHF) of cashmere goat, and found that the FGF5 receptor, fibroblast growth factor receptor 1 (FGFR1), was expressed in these two types of dermal papilla cells. Moreover, adenovirus-mediated overexpression of FGF5 could upregulate the mRNA expression of insulin-like growth factor-1 (IGF-1), versican and noggin that were important for follicle growth maintenance, whereas downregulate the expression of anagen chalone bone morphogenetic protein 4 (BMP4) in dermal papilla cells. However, these alterations were partly reversed by FGF5s overexpression. In conclusion, our results demonstrated that FGF5s acted as an inhibitor of FGF5 in the regulation of anagen-catagen transition of cashmere goat dermal papilla cells.

Two recessive mutations in FGF5 are associated with the long-hair phenotype in donkeys

Background

Seven donkey breeds are recognized by the French studbook. Individuals from the Pyrenean, Provence, Berry Black, Normand, Cotentin and Bourbonnais breeds are characterized by a short coat, while those from the Poitou breed (Baudet du Poitou) are characterized by a long-hair phenotype. We hypothesized that loss-of-function mutations in the FGF5 (fibroblast growth factor 5) gene, which are associated with a long-hair phenotype in several mammalian species, may account for the special coat feature of Poitou donkeys. To the best of our knowledge, mutations in FGF5 have never been described in Equidae.

Methods

We sequenced the FGF5 gene from 35 long-haired Poitou donkeys, as well as from a panel of 67 short-haired donkeys from the six other French breeds and 131 short-haired ponies and horses.

Results

We identified a recessive c.433_434delAT frameshift deletion in FGF5, present in Poitou and three other donkey breeds and a recessive nonsense c.245G > A substitution, present in Poitou and four other donkey breeds. The frameshift deletion was associated with the long-hair phenotype in Poitou donkeys when present in two copies (n = 31) or combined with the nonsense mutation (n = 4). The frameshift deletion led to a stop codon at position 159 whereas the nonsense mutation led to a stop codon at position 82 in the FGF5 protein. In silico, the two truncated FGF5 proteins were predicted to lack the critical β strands involved in the interaction between FGF5 and its receptor, a mandatory step to inhibit hair growth.

Conclusions

Our results highlight the allelic heterogeneity of the long-hair phenotype in donkeys and enlarge the panel of recessive FGF5 loss-of-function alleles described in mammals. Thanks to the DNA test developed in this study, breeders of non-Poitou breeds will have the opportunity to identify long-hair carriers in their breeding stocks.

Electronic supplementary material

The online version of this article (doi:10.1186/s12711-014-0065-5) contains supplementary material, which is available to authorized users.

FGF5 is a crucial regulator of hair length in humans

Mechanisms that regulate the growth of eyelashes have remained obscure. We ascertained two families from Pakistan who presented with familial trichomegaly, or extreme eyelash growth. Using a combination of whole exome sequencing and homozygosity mapping, we identified distinct pathogenic mutations within fibroblast growth factor 5 (FGF5) that underlie the disorder. Subsequent sequencing of this gene in several additional trichomegaly families identified an additional mutation in FGF5. We further demonstrated that hair fibers from forearms of these patients were significantly longer than hairs from control individuals, with an increased proportion in the growth phase, anagen. Using hair follicle organ cultures, we show that FGF5 induces regression of the human hair follicle. We have identified FGF5 as a crucial regulator of hair growth in humans for the first time, to our knowledge, and uncovered a therapeutic target to selectively regulate eyelash growth.

FGF5 as an oncogenic factor in human glioblastoma multiforme: autocrine and paracrine activities

Fibroblast growth factor 5 (FGF5) is widely expressed in embryonic but scarcely in adult tissues. Here we report simultaneous overexpression of FGF5 and its predominant high-affinity receptor (FGFR1 IIIc) in astrocytic brain tumour specimens (N=49) and cell cultures (N=49). The levels of both ligand and receptor increased with enhanced malignancy in vivo and in vitro. Furthermore, secreted FGF5 protein was generally present in the supernatants of glioblastoma (GBM) cells. siRNA-mediated FGF5 downmodulation reduced moderately but significantly GBM cell proliferation while recombinant FGF5 (rFGF5) increased this parameter preferentially in cell lines with low endogenous expression levels. Apoptosis induction by prolonged serum starvation was significantly prevented by rFGF5. Moreover, tumour cell migration was distinctly stimulated by rFGF5 but attenuated by FGF5 siRNA. Blockade of FGFR1-mediated signals by pharmacological FGFR inhibitors or a dominant-negative FGFR1 IIIc protein inhibited GBM cell proliferation and/or induced apoptotic cell death. Moreover, rFGF5 and supernatants of highly FGF5-positive GBM cell lines specifically stimulated proliferation, migration and tube formation of human umbilical vein endothelial cells. In summary, we demonstrate for the first time that FGF5 contributes to the malignant progression of human astrocytic brain tumours by both autocrine and paracrine effects.

Functional diversity of FGF-2 isoforms by intracellular sorting

Regulation of the subcellular localization of certain proteins is a mechanism for the regulation of their biological activities. FGF-2 can be produced as distinct isoforms by alternative initiation of translation on a single mRNA and the isoforms are differently sorted in cells. High molecular weight FGF-2 isoforms are not secreted from the cell, but are transported to the nucleus where they regulate cell growth or behavior in an intracrine fashion. 18 kDa FGF-2 can be secreted to the extracellular medium where it acts as a conventional growth factor by binding to and activation of cell-surface receptors. Furthermore, following receptor-mediated endocytosis, the exogenous FGF-2 can be transported to the nuclei of target cells, and this is of importance for the transmittance of a mitogenic signal. The growth factor is able to interact with several intracellular proteins. Here, the mode of action and biological role of intracellular FGF-2 are discussed.

Comprehensive analysis of FGF and FGFR expression in skin: FGF18 is highly expressed in hair follicles and capable of inducing anagen from telogen stage hair follicles

We quantified the mRNA expression of all 22 fibroblast growth factor family members (FGF) and their four receptors (FGFR) in adult mouse full-thickness skin at various stages of the hair growth cycle. We found that in addition to mRNA encoding FGF previously identified in skin (FGF1, 2, 5, 7, 10, 13, and 22), FGF18 mRNA was also strongly expressed. Expression of these FGF varied throughout hair growth cycle: mRNA expression of FGF18 and 13 peaked at telogen; FGF7 and 10 at anagen V; and FGF5 and 22 at anagen VI. In situ hybridization revealed that FGF18 mRNA is mainly expressed in the anagen inner root sheath and telogen bulge of hair follicles. In culture, FGF18 stimulated DNA synthesis in human dermal fibroblasts, dermal papilla cells, epidermal keratinocytes and vascular endothelial cells. When FGF18 was administered subcutaneously to mice in a uniform telogen state, anagen hair growth was observed. Our findings suggest that FGF18 is important for the regulation of hair growth and the maintenance of skin in adult mice.

Bulge- and basal layer-specific expression of fibroblast growth factor-13 (FHF-2) in mouse skin

A variety of polypeptide growth factors are involved in the dynamic maintenance of the skin and hair. Here, we demonstrate the presence of high levels of fibroblast growth factor (FGF)-13 in the bulge region of hair follicles. Using real-time PCR, we found that expression of FGF-13 mRNA is comparable to, or higher than, that of other FGF known to regulate hair growth and wound healing. To gain additional insight into the function of FGF-13, we evaluated its distribution using in situ hybridization and immunohistochemical staining. Unlike other FGF, the distribution of FGF-13 mRNA and protein in adult mice was mainly restricted to cells in the bulge region of hair follicles, although lower levels were detected with less frequency in keratinocytes in the basal layer of the epidermis. FGF-13 protein was detectable in the bulge region throughout the hair growth cycle, but its distribution was especially wide during telogen and early anagen. During hair follicle morphogenesis in newborn mice, FGF-13 protein was first detected in the bulge region and basal layer keratinocytes 3 d after birth. These findings suggest that FGF-13 may play a role in regulating the function of cells in the bulge region and basal layer of the epidermis.

Signaling, internalization, and intracellular activity of fibroblast growth factor

The fibroblast growth factor (FGF) family contains 23 members in mammals including its prototype members FGF-1 and FGF-2. FGFs have been implicated in regulation of many key cellular responses involved in developmental and physiological processes. These includes proliferation, differentiation, migration, apoptosis, angiogenesis, and wound healing. FGFs bind to five related, specific cell surface receptors (FGFRs). Four of these have intrinsic tyrosine kinase activity. Dimerization of the receptor is a prerequisite for receptor transphosphorylation and activation of downstream signaling molecules. All members of the FGF family have a high affinity for heparin and for cell surface heparan sulfate proteoglycans, which participate in formation of stable and active FGF-FGFR complexes. FGF-mediated signaling is an evolutionarily conserved signaling module operative in invertebrates and vertebrates. It seems that some members of the family have a dual mode of action. FGF-1, FGF-2, FGF-3, and FGF-11-14 have been found intranuclearly as endogenous proteins. Exogenous FGF-1 and FGF-2 are internalized by receptor-mediated endocytosis, in a clathrin-dependent and -independent way. Internalized FGF-1 and FGF-2 are able to cross cellular membranes to reach the cytosol and the nuclear compartment. The role of FGF internalization and the intracellular activity of some FGFs are discussed in the context of the known signaling induced by FGF.

Decapeptide with fibroblast growth factor (FGF)-5 partial sequence inhibits hair growth suppressing activity of FGF-5

Earlier studies demonstrated that knock-out of fibroblast growth factor-5 gene (Fgf-5) prolonged anagen VI phase of hair cycle, resulting long hairs in the mice. We showed the activities on hair growth of the two Fgf-5 gene products, one of which, FGF-5 suppressed hair growth by inhibiting anagen proceeding and inducing the transition from anagen to catagen, and FGF-5S, a shorter polypeptide with FGF-5-antagonizing activity translated from alternatively spliced mRNA, suppressed this activity of FGF-5. As the results suggested that FGF-5 antagonist would increase hair growth, we synthesized various peptides having partial sequences of human FGF-5 and FGF-5S and determined their FGF-5 antagonist activity. Among them, a decapeptide designated P3 (95-VGIGFHLQIY-104) that aligns with receptor binding sites of FGF-1 and FGF-2 suppressed FGF-5-induced proliferation of BALB/3T3 A31 and NIH/3T3 murine fibroblasts, and FGF receptor-1c (FGFR-1c)-transfected Ba/F3 cell line (FR-Ba/F3 cells). IC50s of this peptide on these cell proliferations were 64, 28, 146 microM, respectively. On the other hand, IC50 of this peptide on binding of FGF-5 to the FGFR-1(IIIc)/Fc chimera was 483 microM. Examination in dorsal depilated mice revealed that the P3 peptide reduced the activity of FGF-5 to recover hair pigmentation and hair follicle lengths. The classification of histologically observed skin sections showed FGF-5-induced delations of anagen procedure had reduced by the P3 peptide. The anti-Ki67 antibody staining of hair follicles was inhibited by administration of FGF-5, and this inhibition by FGF-5 was recovered by administration of the P3 peptide. The P3 peptide alone did not affect hair follicle length and hair cell proliferation. These results indicate that the decapeptide antagonized FGF-5 activity in vivo, and reduced the inhibition of FGF-5 in hair growth, confirming that FGF-5 inhibitors are promising substances against hair loss and/or for promoting hair growth.

Notch activation suppresses fibroblast growth factor-dependent cellular transformation

Aberrant activations of the Notch and fibroblast growth factor receptor (FGFR) signaling pathways have been correlated with neoplastic growth in humans and other mammals. Here we report that the suppression of Notch signaling in NIH 3T3 cells by the expression of either the extracellular domain of the Notch ligand Jagged1 or dominant-negative forms of Notch1 and Notch2 results in the appearance of an exaggerated fibroblast growth factor (FGF)-dependent transformed phenotype characterized by anchorage-independent growth in soft agar. Anchorage-independent growth exhibited by Notch-repressed NIH 3T3 cells may result from prolonged FGFR stimulation caused by both an increase in the expression of prototypic and oncogenic FGF gene family members and the nonclassical export of FGF1 into the extracellular compartment. Interestingly, FGF exerts a negative effect on Notch by suppressing CSL (CBF-1/RBP-Jk/KBF2 in mammals, Su(H) in Drosophila and Xenopus, and Lag-2 in Caenorhabditis elegans)-dependent transcription, and the ectopic expression of constitutively active forms of Notch1 or Notch2 abrogates FGF1 release and the phenotypic effects of FGFR stimulation. These data suggest that communication between the Notch and FGFR pathways may represent an important reciprocal autoregulatory mechanism for the regulation of normal cell growth.

Fibroblast growth factor 5 inhibits hair growth by blocking dermal papilla cell activation

Fibroblast growth factor (FGF) 5 inhibits hair growth and induces catagen in mouse hair follicles, in vivo. Given that FGF-5 receptor (FGFR1) is expressed in dermal papilla cells (DPCs), which are known to stimulate outer root sheath cell (ORSC) proliferation, we hypothesized that FGF-5 attenuates DPC-mediated ORSC proliferation. In the present study, DPCs and ORSCs were isolated from rat vibrissae, after which the effects of FGF-5 on proliferation of ORSCs cultured in DPC-conditioned medium were assessed. We first confirmed that FGFR1 was expressed in cultured DPCs and detected FGFR2-4 as well. ORSC proliferation was increased approximately twofold when the cells were cultured in DPC-conditioned medium, and the effect was unaltered by FGF-5. In addition, FGF-5 did not directly inhibit ORSC proliferation; indeed, it actually promoted proliferation of both DPCs and ORSCs. When DPCs were first activated by exposure to FGF-1 and FGF-2, which are expressed in hair follicles during anagen, ORSC proliferation observed in the resultant conditioned medium was substantially greater than in medium conditioned by unstimulated DPCs. The FGF-1-induced enhancement was reversed by FGF-5, diminishing ORSC proliferation to control levels. By contrast, the enhancement of DPC-mediated ORSC proliferation by FGF-2 was not suppressed by FGF-5. Proliferation of ORSCs did not depend on DPC proliferation, nor did FGF-1 directly promote ORSC proliferation. Dermal papillae thus appear to require activation before they will efficiently stimulate hair growth, and FGF-5 appears to inhibit hair growth and induce catagen by blocking that activation.

Axon-Schwann cell interactions regulate the expression of fibroblast growth factor-5 (FGF-5)

We screened for genes whose expression is significantly up- or downregulated during Wallerian degeneration in adult rat sciatic nerve with cDNA arrays. Fibroblast growth factor-5 (FGF-5) mRNA seemed to be induced. This was confirmed by northern blotting and in situ hybridization, as well as Western blotting for FGF-5 in axotomized nerve. Axon-Schwann cell interactions decreased the steady-state level of FGF-5 mRNA in regenerating sciatic nerves, and forskolin diminished its expression in cultured Schwann cells. We conclude that denervated Schwann cells synthesize FGF-5, which is a secreted, neuronotrophic member of the FGF family.

Fibroblast growth factor-5 is expressed in Schwann cells and is not essential for motoneurone survival

Fibroblast growth factor-5 (FGF-5) is a putative target-derived survival factor for motoneurones as it is concentrated in the synaptic portions of skeletal muscles and because it promotes the survival of embryonic motoneurones in vitro. A variety of experimental approaches have been used to examine this possibility. The expression of FGF-5 in the neuromuscular system was analysed using the reverse transcription-polymerase chain reaction (RT-PCR). Both splice variants of FGF-5 were detected in adult rat skeletal muscle, sciatic nerve, and spinal cord. The expression of FGF-5 in skeletal muscle was up-regulated after denervation. At first sight this appears to be consistent with FGF-5 being a target-derived factor. However, FGF-5 protein was detected in Schwann cells, macrophages, vascular smooth muscle and endothelial cells, but not in muscle fibres. The absence of FGF-5 in muscle fibres was confirmed by RT-PCR examination of isolated muscle fibres. Furthermore, FGF-5 protein was also not detected in denervated fibres, as would be expected for a neuronal survival factor. Denervation did however lead to up-regulation of FGF-5 in the Schwann cells of the distal nerve trunk. This may indicate that FGF-5 is either an autocrine regulator of Schwann cells or a Schwann cell-derived neurotrophic factor. The latter appears not to be the case for two reasons. First, the double-ligation technique was used to show that endogenous FGF-5 is not transported in motor axons. Second, stereological estimates of the number of motoneurones in an FGF-5 null mutant (Angora) mouse failed to reveal any loss of motoneurones. Collectively these experiments suggest that FGF-5 is not a physiological regulator of motoneurones, and therefore raise the possibility that it is an autocrine regulator of Schwann cells.

Linkage of sugar chains to a fragment peptide of FGF-5S by a chemoenzymatic strategy and changes in the rate of proteolytic hydrolysis

Various O-linked and N-linked sugar chains were linked enzymatically to a fragment peptide (Leu-Ser-Gln(or Asn)-Val-His-Arg) of FGF-5S. First, galactose was linked with beta-(1-->3)-linkage to GalNAc-linked peptide by a transglycosylation using beta-galactosidase from Bacillus circulans (recombinant). Then sialic acid was linked with the aid of sialyltransferase from rat liver (recombinant) to give NeuAcalpha-(2-->3)-Galbeta-(1-->3)-GalNAc-linked hexapeptide. Further, a sialylated 2-chain biantennary sugar chain was linked by a transglycosylation using endo N-acetyl-beta-D-glucosaminidase from Mucor hiemalis (endo M, recombinant). The activity of DNA synthesis in a fibroblast cell line was increased by this glycosylation. The resistance of the obtained glycopeptides towards proteolytic hydrolysis by rat serum and by five proteases was compared with that of original peptide. The resistance was remarkably enhanced by the glycosylation.

Differential display identification of 40 genes with altered expression in activated human smooth muscle cells. Local expression in atherosclerotic lesions of smags, smooth muscle activation-specific genes

Detailed knowledge on the molecular and cellular mechanisms that control (re)-differentiation of vascular smooth muscle cells (SMCs) is critical to understanding the pathological processes underlying atherogenesis. We identified by differential display/reverse transcriptase-polymerase chain reaction 40 genes with altered expression in cultured SMCs upon stimulation with the conditioned medium of activated macrophages. This set of genes comprises 10 known genes and 30 novel genes, which we call "smags" (for smooth muscle activation-specific genes). To determine the in vivo significance of these (novel) genes in atherogenesis, we performed in situ hybridization experiments on vascular tissue. Specifically, FLICE (Fas-associated death domain-like interleukin-1beta-converting enzyme)-like inhibitory protein (FLIP) is expressed in neointimal SMCs as well as in lesion macrophages and endothelial cells, whereas the expression of the novel genes smag-63, smag-64, and smag-84 is restricted to neointimal SMCs. Characterization of full-length smag-64 cDNA revealed that it encodes a novel protein of 66 amino acids. smag-82 cDNA comprises the complete, unknown, 3'-untranslated region of fibroblast growth factor-5. Collectively, our results illustrate the complex changes of SMC gene expression that occur in response to stimulation with cytokines and growth factors secreted by activated macrophages. Moreover, we identified interesting candidate genes that may play a role in the differentiation of SMCs during atherogenesis.

Dual-mode regulation of hair growth cycle by two Fgf-5 gene products

As the result of alternative mRNA splicing, Fgf-5, the gene encoding fibroblast growth factor-5, translates to both long and short forms of the protein, respectively, designated fibroblast growth factor-5 and fibroblast growth factor-5S. We previously showed that localization of fibroblast growth factor-5 and the level of fibroblast growth factor-5S in murine skin are hair-cycle dependent. In this study, we examined the effect of fibroblast growth factor-5 and fibroblast growth factor-5S on the hair growth cycle in mice. Once the anagen phase of the hair growth cycle was induced in the dorsal skin by depilation during telogen, and effects of subcutaneous injection of fibroblast growth factor-5 and fibroblast growth factor-5S into the affected region were analyzed. We found that fibroblast growth factor-5 inhibited hair growth during anagen and promoted the transition from anagen to catagen. Interestingly, whereas fibroblast growth factor-5S alone exerted no effect on hair growth, it significantly inhibited the catagen-promoting activity of fibroblast growth factor-5 when the two proteins were injected simultaneously. Because neither fibroblast growth factor-5 nor fibroblast growth factor-5S affected skin thickness, it is postulated that changes in skin thickness during hair cycle are separately regulated by factors other than those regulating hair and follicle growth. The present results, together with our earlier findings that fibroblast growth factor-5-producing cells gather around dermal papillae during catagen, whereas fibroblast growth factor-5S is abundantly expressed in the hair follicles only during the latter half of anagen, suggests that the mouse hair growth cycle is regulated by the two Fgf-5 gene products acting in concert: fibroblast growth factor-5 induces catagen, whereas fibroblast growth factor-5S antagonizes this activity during anagen.

Characterization of fibroblast growth factor-6 expressed by Chinese hamster ovary cells as a glycosylated mitogen for human vascular endothelial cells

The gene for fibroblast growth factor (FGF)-6/hst-2 was originally identified by its close homology with the FGF-4/hst-1 gene. Aside from its ability to transform cultured fibroblasts, the characteristics of FGF-6 protein have only been studied using a simple preparation from E. coli. In the present study, we expressed FGF-6 cDNA in CHO cells and characterized the resultant protein. We found that CHO cells secreted several forms of the FGF-6 polypeptide, and that there were multiple N-terminal modifications. The longest form (18-kDa) contained the sequence, SerProAlaGlyAlaArg, as its N-terminus, which was consistent with the signal peptide cleavage site predicted from its primary structure. The core polypeptide was primarily modified by heterogeneous N-glycans that were sialylated to a small degree; among them, biantennary structures were found to predominate. Moreover, possible O-glycosylation was also detected. N-glycosylated FGF-6 potently induced DNA synthesis and proliferation of human vascular endothelial cells, whereas in the absence of N-glycosylation, FGF-6 mitogenicity was substantially diminished. The results clearly indicate that FGF-6 expressed by mammalian cells is a glycosylated mitogen for vascular endothelial cells and further suggests that N-glycosylation plays a key role in determining the mitogenicity of FGF-6.