Novel secretory heparin-binding factors from human glioma cells (glia-activating factors) involved in glial cell growth. Purification and biological properties

The fundamentals of fibroblast growth factor 9

Fibroblast growth factor 9 (FGF9) was first identified during a screen for factors acting on cells of the central nervous system (CNS). Research over the subsequent two decades has revealed this protein to be a critically important and elegantly regulated growth factor. A hallmark control feature is reciprocal compartmentalization, particularly during development, with epithelium as a dominant source and mesenchyme a prime target. This mesenchyme selectivity is accomplished by the high affinity of FGF9 to the IIIc isoforms of FGFR1, 2, and 3. FGF9 is expressed widely in the embryo, including the developing heart and lungs, and more selectively in the adult, including the CNS and kidneys. Global Fgf9-null mice die shortly after birth due to respiratory failure from hypoplastic lungs. As well, their hearts are dilated and poorly vascularized, the skeleton is small, the intestine is shortened, and male-to-female sex reversal can be found. Conditional Fgf9-null mice have revealed CNS phenotypes, including ataxia and epilepsy. In humans, FGF9 variants have been found to underlie multiple synostoses syndrome 3, a syndrome characterized by multiple joint fusions. Aberrant FGF9 signaling has also been implicated in differences of sex development and cancer, whereas vascular stabilizing effects of FGF9 could benefit chronic diseases. This primer reviews the attributes of this vital growth factor.

FGF9, a Potent Mitogen, Is a New Ligand for Integrin αvβ3, and the FGF9 Mutant Defective in Integrin Binding Acts as an Antagonist

FGF9 is a potent mitogen and survival factor, but FGF9 protein levels are generally low and restricted to a few adult organs. Aberrant expression of FGF9 usually results in cancer. However, the mechanism of FGF9 action has not been fully established. Previous studies showed that FGF1 and FGF2 directly bind to integrin αvβ3, and this interaction is critical for signaling functions (FGF-integrin crosstalk). FGF1 and FGF2 mutants defective in integrin binding were defective in signaling, whereas the mutants still bound to FGFR suppressed angiogenesis and tumor growth, indicating that they act as antagonists. We hypothesize that FGF9 requires direct integrin binding for signaling. Here, we show that docking simulation of the interaction between FGF9 and αvβ3 predicted that FGF9 binds to the classical ligand-binding site of αvβ3. We show that FGF9 bound to integrin αvβ3 and generated FGF9 mutants in the predicted integrin-binding interface. An FGF9 mutant (R108E) was defective in integrin binding, activating FRS2α and ERK1/2, inducing DNA synthesis, cancer cell migration, and invasion in vitro. R108E suppressed DNA synthesis and activation of FRS2α and ERK1/2 induced by WT FGF9 (dominant-negative effect). These findings indicate that FGF9 requires direct integrin binding for signaling and that R108E has potential as an antagonist to FGF9 signaling.

Transcriptome Profiling Identifies Differentially Expressed Genes in Skeletal Muscle Development in Native Chinese Ducks

China boasts a rich diversity of indigenous duck species, some of which exhibit desirable economic traits. Here, we generated transcriptome sequencing datasets of breast muscle tissue samples from 1D of four groups: Pekin duck pure breeding group (P), Jinling White duck breeding group (J), P ♂ × J ♀ orthogonal group (PJ) and J ♂ × P ♀ reciprocal-cross group (JP) (n = 3), chosen based on the distinctive characteristics of duck muscle development during the embryonic period. We identified 5053 differentially expressed genes (DEGs) among the four groups. Network prediction analysis showed that ribosome and oxidative phosphorylation-related genes were the most enriched, and muscular protein-related genes were found in the 14-day-old embryonic group. We found that previously characterized functional genes, such as FN1, AGRN, ADNAMST3, APOB and FGF9, were potentially involved in muscle development in 14-day-old embryos. Functional enrichment analysis suggested that genes that participated in molecular function and cell component and key signaling pathways (e.g., hippo, ribosome, oxidative phosphorylation) were significantly enriched in the development of skeletal muscle at 14 days of embryonic age. These results indicate a possible role of muscle metabolism and myoglobin synthesis in skeletal muscle development in both duck parents and hybrids.

FGF9, a potent mitogen, is a new ligand for integrin αvβ3, and the FGF9 mutant defective in integrin binding acts as an antagonist

FGF9 is a potent mitogen and survival factor, but FGF9 protein level is generally low and restricted to a few adult organs. Aberrant expression of FGF9 usually results in cancer. However, the mechanism of FGF9 action has not been fully established. Previous studies showed that FGF1 and FGF2 directly bind to integrin αvβ3 and this interaction is critical for signaling functions (FGF-integrin crosstalk). FGF1 and FGF2 mutants defective in integrin binding were defective in signaling, whereas the mutants still bound to FGFR, and suppressed angiogenesis and tumor growth, indicating that they act as antagonists. We hypothesize that FGF9 requires direct integrin binding for signaling. Here we show that docking simulation of interaction between FGF9 and αvβ3 predicted that FGF9 binds to the classical ligand-binding site of αvβ3. We showed that FGF9 actually bound to integrin αvβ3, and generated an FGF9 mutants in the predicted integrin-binding interface. An FGF9 mutant (R108E) was defective in integrin binding, activating FRS2α and ERK1/2, inducing DNA synthesis, cancer cell migration, and invasion in vitro. R108E suppressed DNA synthesis induced by WT FGF9 and suppressed DNA synthesis and activation of FRS2α and ERK1/2 induced by WT FGF9 (dominant-negative effect). These findings indicate that FGF9 requires direct integrin binding for signaling and that R108E has potential as an antagonist to FGF9 signaling.

A New Risk Score Based on Eight Hepatocellular Carcinoma- Immune Gene Expression Can Predict the Prognosis of the Patients

Background

Hepatocellular carcinoma (HCC) is one of the malignant tumors with high morbidity and mortality worldwide. Immunotherapy has emerged as an increasingly important cancer treatment modality. However, the potential relationship between immune genes and HCC still needs to be explored. The purpose of this study is to construct a new prognostic risk signature to predict the prognosis of HCC patients based on the expression of immune-related genes (IRGs) and explore its potential mechanism.

Methods

We analyzed the gene expression data of 332 HCC patient samples and 46 adjacent normal tissues samples (Solid Tissue Normal including cirrhotic tissue) in The Cancer Genome Atlas (TCGA) database and clinical characteristics. We analyzed the gene expression data, identified differentially expressed IRGs in HCC tissues, filtered IRGs with prognostic value to construct an IRG signature, and classified patients into high and low gene expression groups based on the expression of IRGs in their tumor tissues. We also investigated the potential molecular mechanisms of IRGs through a bioinformatics approach using Protein-Protein Interaction (PPI) network, Kyoto Encyclopedia of Genes and Genomes (KEGG) database analysis and Gene Ontology (GO) database analysis. Differentially expressed IRGs associated with significant clinical outcomes (SIRGs) were identified by univariate Cox regression analysis. An immune-related risk score model (IRRSM) was established based on Lasso Cox regression analysis and multivariate Cox regression analysis. Based on the IRRSM, the immune score of the patients was calculated, and the patients were divided into high-risk and low-risk patients according to the median score, and the differences in survival between the two groups were compared. Then, the correlation analysis between the IRRSM and clinical characteristics was performed, and the IRRSM was validated using the International Cancer Genome Consortium (ICGC) database.

Results

The IRRSM was eventually constructed and confirmed to be an independent prognostic model for HCC patients. The IRRSM was shown to be positively correlated with the infiltration of four types of immune cells.

Conclusion

Our results showed that some SIRGs have potential value for predicting the prognosis and clinical outcomes of HCC patients. IRGs affect the prognosis of HCC patients by regulating the tumor immune microenvironment (TIME). This study provides a new insight for immune research and treatment strategies in HCC patients.

The Fibroblast Growth Factor 9 (Fgf9) Participates in Palatogenesis by Promoting Palatal Growth and Elevation

Cleft palate, a common global congenital malformation, occurs due to disturbances in palatal growth, elevation, contact, and fusion during palatogenesis. The Fibroblast growth factor 9 (FGF9) mutation has been discovered in humans with cleft lip and palate. Fgf9 is expressed in both the epithelium and mesenchyme, with temporospatial diversity during palatogenesis. However, the specific role of Fgf9 in palatogenesis has not been extensively discussed. Herein, we used Ddx4-Cre mice to generate an Fgf9^–/– mouse model (with an Fgf9 exon 2 deletion) that exhibited a craniofacial syndrome involving a cleft palate and deficient mandibular size with 100% penetrance. A smaller palatal shelf size, delayed palatal elevation, and contact failure were investigated to be the intrinsic causes for cleft palate. Hyaluronic acid accumulation in the extracellular matrix (ECM) sharply decreased, while the cell density correspondingly increased in Fgf9^–/– mice. Additionally, significant decreases in cell proliferation were discovered in not only the palatal epithelium and mesenchyme but also among cells in Meckel’s cartilage and around the mandibular bone in Fgf9^–/– mice. Serial sections of embryonic heads dissected at embryonic day 14.5 (E14.5) were subjected to craniofacial morphometric measurement. This highlighted the reduced oral volume owing to abnormal tongue size and descent, and insufficient mandibular size, which disturbed palatal elevation in Fgf9^–/– mice. These results indicate that Fgf9 facilitates palatal growth and timely elevation by regulating cell proliferation and hyaluronic acid accumulation. Moreover, Fgf9 ensures that the palatal elevation process has adequate space by influencing tongue descent, tongue morphology, and mandibular growth.

DJ-1 promotes epithelial-to-mesenchymal transition via enhancing FGF9 expression in colorectal cancer

Tumor metastasis is the main contributor to high recurrence and mortality in colorectal cancer (CRC). In a previous study, we found that DJ-1 plays an important role in CRC metastasis, and is the main target in Ciclopirox olamine (CPX)-treated CRC. However, the mechanism underlying DJ-1-induced CRC metastasis remains elusive. In the present study, our results showed that DJ-1 could activate Wnt signaling resulting in enhanced invasive potential and epithelial-to-mesenchymal transition (EMT) in CRC cells. RNA-seq and bioinformatics analysis reveals that the DJ-1/Wnt signaling pathway may promote CRC cells' EMT by regulating fibroblast growth factor 9 (FGF9) expression. Molecular validation showed that expression of FGF9 was upregulated by the DJ-1/Wnt signaling pathway and decreasing FGF9-expression impeded DJ-1-induced CRC invasive ability and EMT, suggesting that FGF9 is involved in DJ-1-enhanced CRC metastasis. In addition, we show that FGF9 was overexpressed in CRC human specimens and was significantly associated with tumor differentiation. High FGF9 expression was correlated with worse overall survival, and a correlation exhibited between FGF9 and EMT markers (E-cadherin and Vimentin) in CRC samples. Together, our results determined that FGF9 was involved in DJ-1-induced invasion and EMT in CRC cells, and may represent a promising therapeutic candidate for CRC anti-metastatic strategies.

Abnormal Expression of Fgf9 during the Development of the Anorectum in Rat Embryos with Anorectal Malformations

The study objective was to investigate the role of fibroblast growth factor 9 (Fgf9) in normal and anorectal malformation (ARM) embryos during the development of the anorectum. Fgf9 expression was assayed in both normal rat embryos and embryos with ARM induced by exposure to ethylenethiourea (ETU) on embryonic day 10 (E10). Fgf9 expression was assayed by immunohistochemical staining, Western blotting, and real-time quantitative polymerase chain reaction (qRT-PCR). Immunohistochemical staining revealed spatiotemporal changes in Fgf9 expression between E13 and E16. Fgf9-positive cells predominated in the mesenchyme of the cloaca on E13 and E14 and at the fusion site of the urorectal septum and cloacal membrane, rectal epithelium, and anal membrane on E15. Fgf9-positive cells were obviously decreased after the anal membrane ruptured on E16. Fgf9-positive staining was significantly decreased in embryos with ARM compared with normal embryos from E13 to E15. The results of Western blots and qRT-PCR were consistent, with significantly increased Fgf9 expression in the hindgut and rectum of normal embryos than in embryos with ARM from E13 to E15. However, there was no difference between the two groups on E16. These results suggested that the anorectal embryogenesis might depend on the induction of Fgf9 signal. The expression of Fgf9 was downregulated in ETU-induced ARM embryos, which might be related to the development of ARM.

Haplotypes of coping behavior associated QTL regions reveal distinct transcript profiles in amygdala and hippocampus

Stress response and coping behavior in pigs are largely shaped by hypothalamic-pituitary-adrenal axis and sympatho-adrenomedullary system action. However, the dynamic interaction between amygdala and hippocampus crucially modulates the behavioral response towards significant emotional events. While this functional relationship is well documented, the molecular underpinnings still remain insufficiently understood. Our study used transcriptome profiling of porcine amygdala and hippocampus to identify molecular pathways that are differentially activated depending on the haplotype of a significantly coping behavior-associated region on pig chromosome 12 (SSC12). The pigs were classified into two groups based on the haplotype information of this QTL-region discovered in our previous genome-wide association study. Ten each of high- (HR) and low- (LR) reactive pigs (n = 20) were selected for differential gene expression analysis and weighted gene co-expression analysis with subsequent pathway analysis. Differentially expressed genes identified in the amygdala include SELL, CXCR7 and NTS, while TRAF3, PTGS2 and CFI were detected in the hippocampus indicating a role of neuroinflammation and immunological processes. Pathway analysis revealed IL-8 signaling, NF-κB signaling, glutamate and GABA metabolism, glucocorticoid receptor signaling and chemokine signaling in the amygdala and ephrin receptor signaling, as well as NF-κB signaling in the hippocampus. We discovered candidate genes in regions detected by genome-wide association study including ARRB2, ADRBK2, THRB, NEK7 and ACVR2B, which relate to dopaminergic and other monoaminergic neurotransmitter systems, neuroimmunomodulation, neuroinflammation and GABA-ergic neurotransmission. These findings provide insights into the molecular underpinning of divergent coping behavior and associated haplotypes in limbic forebrain system in pig.

Oil body bound oleosin-rhFGF9 fusion protein expressed in safflower (Carthamus tinctorius L.) stimulates hair growth and wound healing in mice

Background

Fibroblast growth factor 9 (FGF9) is a heparin-binding growth factor, secreted by both mesothelial and epithelial cells, which participates in hair follicle regeneration, wound healing, and bone development. A suitable source of recombinant human FGF9 (rhFGF9) is needed for research into potential clinical applications. We present that expression of oleosin-rhFGF9 fusion protein in safflower (Carthamus tinctorius L.) seeds stimulates hair growth and wound healing.

Results

The oleosin-rhFGF9 expressed in safflower seeds, in which it localizes to the surface of oil bodies. The expression of oleosin-rhFGF9 was confirmed by polyacrylamide gel electrophoresis and western blotting. According to BCA and Enzyme-linked immunosorbent assay (ELISA) assay, the results show that the expression level of oleosin-rhFGF9 was 0.14% of oil body protein. The oil body bound oleosin-rhFGF9 showed mitogenic activity towards NIH3T3 cells in a methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. The efficacy of oil body bound oleosin-rhFGF9 in promoting hair growth and wound healing was investigated in C57BL/6 mice. In a hair regeneration experiment, 50 μg/μl oil body bound oleosin-rhFGF9 was applied to the dorsal skin of mice in the resting phase of the hair growth cycle. After 15 days, thicker hair and increased number of new hairs were seen compared with controls. Furthermore, the number of new hairs was greater compared with rhFGF9-treated mice. The hair follicles of mice treated with oil body bound oleosin-rhFGF9 expressed β-catenin more abundantly. In a wound healing experiment, dorsal skin wounds were topically treated with 50 μg/μl oil body bound oleosin-rhFGF9. Wound healing was quicker compared with mice treated with rhFGF9 and controls, especially in the earlier stages of healing.

Conclusions

The oil body bound oleosin-rhFGF9 promotes both hair growth and wound healing. It appears to promote hair growth, at least in part, by up-regulating β-catenin expression. The potential of oil body bound oleosin-rhFGF9 as an external drug can treat the alopecia and wounds or use in further clinical application.

Electronic supplementary material

The online version of this article (10.1186/s12896-018-0433-2) contains supplementary material, which is available to authorized users.

MicroRNA-182 prevents vascular smooth muscle cell dedifferentiation via FGF9/PDGFRβ signaling

The abnormal phenotypic transformation of vascular smooth muscle cells (SMCs) causes various proliferative vascular diseases. MicroRNAs (miRNAs or miRs) have been established to play important roles in SMC biology and phenotypic modulation. This study revealed that the expression of miR‑182 was markedly altered during rat vascular SMC phenotypic transformation in vitro. We aimed to investigate the role of miR‑182 in the vascular SMC phenotypic switch and to determine the potential molecular mechanisms involved. The expression of miR‑182 gene was significantly downregulated in cultured SMCs during dedifferentiation from a contractile to a synthetic phenotype. Conversely, the upregulation of miR‑182 increased the expression of SMC-specific contractile genes, such as α-smooth muscle actin, smooth muscle 22α and calponin. Additionally, miR‑182 overexpression potently inhibited SMC proliferation and migration under both basal conditions and under platelet-derived growth factor-BB stimulation. Furthermore, we identified fibroblast growth factor 9 (FGF9) as the target gene of miR‑182 for the phenotypic modulation of SMCs mediated through platelet-derived growth factor receptor β (PDGFRβ) signaling. These data suggest that miR‑182 may be a novel SMC phenotypic marker and a modulator that may be used to prevent SMC dedifferentiation via FGF9/PDGFRβ signaling.

Fibroblast growth factor 9 activates akt and MAPK pathways to stimulate steroidogenesis in mouse leydig cells

Fibroblast growth factor 9 (FGF9) is a multifunctional polypeptide belonging to the FGF family and has functions related to bone formation, lens-fiber differentiation, nerve development, gap-junction formation and sex determination. In a previous study, we demonstrated that FGF9 stimulates the production of testosterone in mouse Leydig cells. In the present study, we used both primary mouse Leydig cells and MA-10 mouse Leydig tumor cells to further investigate the molecular mechanism of FGF9-stimulated steroidogenesis. Results showed that FGF9 significantly activated steroidogenesis in both mouse primary and tumor Leydig cells (p<0.05). Furthermore, FGF9 significantly induced the expression of phospho-Akt at 0.5 and 24 hr, phospho-JNK at 0.25, 0.5, and 24 hr, phospho-p38 at 0.5 hr, and phospho-ERK1/2 from 0.25 to 24 hr in primary Leydig cells (p<0.05). Also, FGF9 significantly up-regulated the expression of phospho-Akt at 3 hr, phospho-JNK at 0.25 hr, and phospho-ERK1/2 at 1 and 3 hr in MA-10 cells (p<0.05). Using specific inhibitors of Akt, JNK, p38, and ERK1/2, we further demonstrated that the inhibitors of Akt and ERK1/2 significantly suppressed the stimulatory effect of FGF9 on steroidogenesis in mouse Leydig cells. In conclusion, FGF9 specifically activated the Akt and ERK1/2 in normal mouse Leydig cells and the Akt, JNK and ERK1/2 in MA-10 mouse Leydig tumor cells to stimulate steroidogenesis.

Overexpression of FGF9 in colon cancer cells is mediated by hypoxia-induced translational activation

Human fibroblast growth factor 9 (FGF9) is a potent mitogen involved in many physiological processes. Although FGF9 messenger RNA (mRNA) is ubiquitously expressed in embryos, FGF9 protein expression is generally low and restricted to a few adult organs. Aberrant expression of FGF9 usually results in human malignancies including cancers, but the mechanism remains largely unknown. Here, we report that FGF9 protein, but not mRNA, was increased in hypoxia. Two sequence elements, the upstream open reading frame (uORF) and the internal ribosome entry site (IRES), were identified in the 5' UTR of FGF9 mRNA. Functional assays indicated that FGF9 protein synthesis was normally controlled by uORF-mediated translational repression, which kept the protein at a low level, but was upregulated in response to hypoxia through a switch to IRES-dependent translational control. Our data demonstrate that FGF9 IRES functions as a cellular switch to turn FGF9 protein synthesis ‘on’ during hypoxia, a likely mechanism underlying FGF9 overexpression in cancer cells. Finally, we provide evidence to show that hypoxia-induced translational activation promotes FGF9 protein expression in colon cancer cells. Altogether, this dynamic working model may provide a new direction in anti-tumor therapies and cancer intervention.

Transcriptome sequencing of gene expression in the brain of the HIV-1 transgenic rat

The noninfectious HIV-1 transgenic (HIV-1Tg) rat was developed as a model of AIDs-related pathology and immune dysfunction by manipulation of a noninfectious HIV-1^gag-pol virus with a deleted 3-kb SphI-MscI fragment containing the 3′ -region of gag and the 5′ region of pol into F344 rats. Our previous studies revealed significant behavioral differences between HIV-1Tg and F344 control rats in their performance in the Morris water maze and responses to psychostimulants. However, the molecular mechanisms underlying these behavioral differences remain largely unknown. The primary goal of this study was to identify differentially expressed genes and enriched pathways affected by the gag-pol-deleted HIV-1 genome. Using RNA deep sequencing, we sequenced RNA transcripts in the prefrontal cortex, hippocampus, and striatum of HIV-1Tg and F344 rats. A total of 72 RNA samples were analyzed (i.e., 12 animals per group × 2 strains × 3 brain regions). Following deep-sequencing analysis of 50-bp paired-end reads of RNA-Seq, we used Bowtie/Tophat/Cufflinks suites to align these reads into transcripts based on the Rn4 rat reference genome and to measure the relative abundance of each transcript. Statistical analyses on each brain region in the two strains revealed that immune response- and neurotransmission-related pathways were altered in the HIV-1Tg rats, with brain region differences. Other neuronal survival-related pathways, including those encoding myelin proteins, growth factors, and translation regulators, were altered in the HIV-1Tg rats in a brain region-dependent manner. This study is the first deep-sequencing analysis of RNA transcripts associated the HIV-1Tg rat. Considering the functions of the pathways and brain regions examined in this study, our findings of abnormal gene expression patterns in HIV-1Tg rats suggest mechanisms underlying the deficits in learning and memory and vulnerability to drug addiction and other psychiatric disorders observed in HIV-positive patients.

Effects of fibroblast growth factor 9 (FGF9) on steroidogenesis and gene expression and control of FGF9 mRNA in bovine granulosa cells

Gene expression of fibroblast growth factor-9 (FGF9) is decreased in granulosa cells (GC) of cystic follicles compared with normal dominant follicles in cattle. The objectives of this study were to investigate the effects of FGF9 on GC steroidogenesis, gene expression, and cell proliferation and to determine the hormonal control of GC FGF9 production. GC were collected from small (1-5 mm) and large (8-22 mm) bovine follicles and treated in vitro with various hormones in serum-free medium for 24 or 48 h. In small- and large-follicle GC, FGF9 inhibited (P < 0.05) IGF-I-, dibutyryl cAMP-, and forskolin-induced progesterone and estradiol production. In contrast, FGF9 increased (P < 0.05) GC numbers induced by IGF-I and 10% fetal calf serum. FGF9 inhibited (P < 0.05) FSHR and CYP11A1 mRNA abundance in small- and large-follicle GC but had no effect (P > 0.10) on CYP19A1 or StAR mRNA. In the presence of a 3β-hydroxysteroid dehydrogenase inhibitor, trilostane, FGF9 also decreased (P < 0.05) pregnenolone production. IGF-I inhibited (P < 0.05) whereas estradiol and FSH had no effect (P > 0.10) on FGF9 mRNA abundance. TNFα and wingless-type mouse mammary tumor virus integration site family member-3A decreased (P < 0.05) whereas T(4) and sonic hedgehog increased (P < 0.05) FGF9 mRNA abundance in control and IGF-I-treated GC. Thus, GC FGF9 gene expression is hormonally regulated, and FGF9 may act as an autocrine regulator of ovarian function by slowing follicular differentiation via inhibiting IGF-I action, gonadotropin receptors, the cAMP signaling cascade, and steroid synthesis while stimulating GC proliferation in cattle.

Relationship between the localization of fibroblast growth factor 9 in prostate cancer cells and postoperative recurrence

BACKGROUND

Fibroblast growth factor 9 (FGF9) enhances cell proliferation and invasiveness in several malignant diseases. The aim of the present study is to investigate the role of FGF9 in postoperative recurrence after radical prostatectomy.

METHODS

Cell viability and invasion of LNCaP cells were assessed using MTT assay and Matrigel invasion assay, respectively, in the presence or absence of treatment with recombinant FGF9. Tissues obtained during a radical prostatectomy in 133 male patients were immunohistochemically stained using anti-FGF9 antibody.

RESULTS

Cell viability and invasion of LNCaP was significantly enhanced by treatment with recombinant FGF9. Immunohistochemical staining detected FGF9-positive cells in 20 samples. The prevalence of FGF9-positive cells in cases with a Gleason score of 8 or higher was 34.2%, which was significantly higher than that in those with Gleason scores of 7 or lower (7.3%, P=0.0003), respectively. The 3-year biochemical relapse-free survival rate was 17.5% in cases with FGF9-positive cells, which was significantly lower than that in cases in which FGF9-positive cells were not detectable (75.5%, P < 0.0001).

CONCLUSIONS

These results indicate that FGF9 can stimulate proliferation and invasion in prostate cancer cells, thus FGF9 could be a candidate of a predictive factor for recurrence after radical prostatectomy.

Fibroblast growth factor 9 delivery during angiogenesis produces durable, vasoresponsive microvessels wrapped by smooth muscle cells

The therapeutic potential of angiogenic growth factors has not been realized. This may be because formation of endothelial sprouts is not followed by their muscularization into vasoreactive arteries. Using microarray expression analysis, we discovered that fibroblast growth factor 9 (FGF9) was highly upregulated as human vascular smooth muscle cells (SMCs) assemble into layered cords. FGF9 was not angiogenic when mixed with tissue implants or delivered to the ischemic mouse hind limb, but instead orchestrated wrapping of SMCs around neovessels. SMC wrapping in implants was driven by sonic hedgehog-mediated upregulation of PDGFRβ. Computed tomography microangiography and intravital microscopy revealed that microvessels formed in the presence of FGF9 had enhanced capacity to receive flow and were vasoreactive. Moreover, the vessels persisted beyond 1 year, remodeling into multilayered arteries paired with peripheral nerves. This mature physiological competency was attained by targeting mesenchymal cells rather than endothelial cells, a finding that could inform strategies for therapeutic angiogenesis and tissue engineering.

New insights into the pathogenesis of cystic follicles in cattle: microarray analysis of gene expression in granulosa cells

Ovarian follicular growth and development are regulated by extraovarian and intraovarian factors, which influence granulosa cell proliferation and differentiation. However, the molecular mechanisms that drive follicular growth are not completely understood. Ovarian follicular cysts are one of the most common causes of reproductive failure in dairy cattle. Nevertheless, the primary cause of cyst formation has not been clearly established. A gene expression comparison may aid in elucidating the causes of ovarian cyst disease. Our objective was to identify differentially expressed genes in ovarian granulosa cells between normal dominant and cystic follicles of cattle. Granulosa cells and follicular fluid were isolated from dominant and cystic follicles collected via either ultrasound-guided aspiration from dairy cows (n = 24) or slaughterhouse ovaries from beef cows (n = 23). Hormonal analysis for progesterone, estradiol, and androstenedione in follicular fluid was performed by RIA. Total RNA was extracted and hybridized to 6 Affymetrix GeneChip Bovine Genome Arrays (Affymetrix, Santa Clara, CA). Abundance of mRNA for differentially expressed selected genes was determined through quantitative real-time reverse-transcription PCR. Follicular cysts showed greater (P < 0.05) progesterone, lesser (P < 0.05) estradiol, and no differences (P > 0.10) in androstenedione concentrations compared with noncystic follicles. A total of 163 gene sequences were differentially expressed (P < 0.01), with 19 upregulated and 144 downregulated. From selected target genes, quantitative real-time reverse-transcription PCR confirmed angiogenin, PGE(2) receptor 4, and G-protein coupled receptor 34 genes as upregulated in cystic follicles, and Indian hedgehog protein precursor and secreted frizzled-related protein 4 genes as downregulated in cystic follicles. Further research is required to elucidate the role of these factors in follicular development and cyst formation.

Research resource: Comprehensive expression atlas of the fibroblast growth factor system in adult mouse

Although members of the fibroblast growth factor (FGF) family and their receptors have well-established roles in embryogenesis, their contributions to adult physiology remain relatively unexplored. Here, we use real-time quantitative PCR to determine the mRNA expression patterns of all 22 FGFs, the seven principal FGF receptors (FGFRs), and the three members of the Klotho family of coreceptors in 39 different mouse tissues. Unsupervised hierarchical cluster analysis of the mRNA expression data reveals that most FGFs and FGFRs fall into two groups the expression of which is enriched in either the central nervous system or reproductive and gastrointestinal tissues. Interestingly, the FGFs that can act as endocrine hormones, including FGF15/19, FGF21, and FGF23, cluster in a third group that does not include any FGFRs, underscoring their roles in signaling between tissues. We further show that the most recently identified Klotho family member, Lactase-like, is highly and selectively expressed in brown adipose tissue and eye and can function as an additional coreceptor for FGF19. This FGF atlas provides an important resource for guiding future studies to elucidate the physiological functions of FGFs in adult animals.

Fibroblast growth factor 9 upregulates heme oxygenase-1 and gamma-glutamylcysteine synthetase expression to protect neurons from 1-methyl-4-phenylpyridinium toxicity

Oxidative stress and lower levels of trophic factors involved in nigrostriatal dopaminergic neurodegeneration are a hallmark of Parkinson disease. Our previous studies found that fibroblast growth factor 9 (FGF9) prevented 1-methyl-4-phenylpyridinium (MPP(+))-induced nigral dopaminergic neuron death and was involved in the neuroprotection of the antioxidant melatonin. However, the protective mechanisms mediated by FGF9 remain unclear. Herein, we explored whether FGF9 regulated the cellular antioxidant defense protecting dopaminergic neurons against MPP(+) intoxication. We found that FGF9 treatment alone induced a decrease in hydrogen peroxide (H(2)O(2)) level, an increase in glutathione content, and an upregulation of gamma-glutamylcysteine synthetase (gamma-GCS) and heme oxygenase 1 (HO-1) expression in primary cortical neurons but not in astrocytes. Simultaneous treatment with FGF9 and MPP(+) prevented MPP(+)-induced neuron death and H(2)O(2) overproduction but did not affect the FGF9-increased gamma-GCS and HO-1 protein expression. Inhibition of gamma-GCS or HO-1 prevented the inhibitory effect of FGF9 on MPP(+)-induced H(2)O(2) production and death in mesencephalic dopaminergic and cortical neurons. However, in the absence of MPP(+), the FGF9-induced H(2)O(2) reduction was blocked by HO-1 inhibitors, but not by gamma-GCS inhibitors. These results indicate that FGF9 upregulates gamma-GCS and HO-1 expression to protect cortical and dopaminergic neurons from MPP(+)-induced oxidative insult.

AUF1 p42 isoform selectively controls both steady-state and PGE2-induced FGF9 mRNA decay

Fibroblast growth factor 9 (FGF9) is an autocrine/paracrine growth factor that plays vital roles in many physiologic processes including embryonic development. Aberrant expression of FGF9 causes human diseases and thus it highlights the importance of controlling FGF9 expression; however, the mechanism responsible for regulation of FGF9 expression is largely unknown. Here, we show the crucial role of an AU-rich element (ARE) in FGF9 3′-untranslated region (UTR) on controlling FGF9 expression. Our data demonstrated that AUF1 binds to this ARE to regulate FGF9 mRNA stability. Overexpression of each isoform of AUF1 (p37, p40, p42 and p45) showed that only the p42 isoform reduced the steady-state FGF9 mRNA. Also, knockdown of p42^AUF1 prolonged the half-life of FGF9 mRNA. The induction of FGF9 mRNA in prostaglandin (PG) E₂-treated human endometrial stromal cells was accompanied with declined cytoplasmic AUF1. Nevertheless, ablation of AUF1 led to sustained elevation of FGF9 expression in these cells. Our study demonstrated that p42^AUF1 regulates both steady-state and PGE₂-induced FGF9 mRNA stability through ARE-mediated mRNA degradation. Since almost half of the FGF family members are ARE-containing genes, our findings also suggest that ARE-mediated mRNA decay is a common pathway to control FGFs expression, and it represents a novel RNA regulon to coordinate FGFs homeostasis in various physiological conditions.

Fibroblast growth factor-9 inhibits astrocyte differentiation of adult mouse neural progenitor cells

Fibroblast growth factor-9 (FGF9) is expressed in the CNS and is reported to be a mitogen for glial cells, to promote neuronal survival, and to retard oligodendrocyte differentiation. Here we examined the effects of FGF9 on the differentiation, survival, and proliferation of adult neural progenitor cells derived from the adult mouse subventricular zone. FGF9 by itself induced neurosphere proliferation, but its effects were modest compared with those of epidermal growth factor and FGF2. When neurospheres were dissociated and plated for differentiation, FGF9 increased total cell number over time in a dose-dependent manner. Ki67 immunostaining and bromodeoxyuridine incorporation indicated that this was at least partially due to the continued presence of proliferative nestin-positive neural progenitor cells and betaIII tubulin-positive neuronal precursors. FGF9 also promoted cell survival as indicated by a decreased number of TUNEL-positive cells over time. Assessment of differentiation showed that FGF9 increased neuron generation that reflected the increase in total cell number; however, the percentage of progenitor cells differentiating into neurons was slightly decreased. FGF9 had a modest effect on oligodendrocyte generation, although it appeared to slow the maturation of oligodenrocytes at higher concentrations. The most marked effect on differentiation was an almost total lack of glial fibrillary acidic protein (GFAP)-positive astrocytes up to 7 days following FGF9 addition, indicating that astrocyte differentiation was strongly inhibited. Total inhibition required prolonged treatment, although a 1-hr pulse was sufficient for partial inhibition, and bone morphogenic protein-4 could partially overcome the FGF9 inhibition of astrocyte differentiation. FGF9 therefore has multiple effects on adult neural precursor cell function, enhancing neuronal precursor proliferation and specifically inhibiting GFAP expression.

Neuron-derived FGF9 is essential for scaffold formation of Bergmann radial fibers and migration of granule neurons in the cerebellum

Although fibroblast growth factor 9 (FGF9) is widely expressed in the central nervous system (CNS), the function of FGF9 in neural development remains undefined. To address this question, we deleted the Fgf9 gene specifically in the neural tube and demonstrated that FGF9 plays a key role in the postnatal migration of cerebellar granule neurons. Fgf9-null mice showed severe ataxia associated with disrupted Bergmann fiber scaffold formation, impaired granule neuron migration, and upset Purkinje cell maturation. Ex vivo cultured wildtype or Fgf9-null glia displayed a stellate morphology. Coculture with wildtype neurons, but not Fgf9-deficient neurons, or treating with FGF1 or FGF9 induced the cells to adopt a radial glial morphology. In situ hybridization showed that Fgf9 was expressed in neurons and immunostaining revealed that FGF9 was broadly distributed in both neurons and Bergmann glial radial fibers. Genetic analyses revealed that the FGF9 activities in cerebellar development are primarily transduced by FGF receptors 1 and 2. Furthermore, inhibition of the MAP kinase pathway, but not the PI3K/AKT pathway, abrogated the FGF activity to induce glial morphological changes, suggesting that the activity is mediated by the MAP kinase pathway. This work demonstrates that granule neurons secrete FGF9 to control formation of the Bergmann fiber scaffold, which in turn, guides their own inward migration and maturation of Purkinje cells.

Microarray analysis of cultured human brain aggregates following cortisol exposure: implications for cellular functions relevant to mood disorders

Increased cortisol levels in humans are often observed in patients suffering from mood disorders. In this study human fetal brain aggregates were exposed to cortisol at 500 nM for 3 weeks, as an in-vitro model of chronic cortisol exposure. Microarray analysis on extracted mRNA using the Affymetrix U133A platform was then performed. Our results demonstrated a significant effect of cortisol on 1648 transcripts; 736 up-regulated and 912 down-regulated genes. The most differentially regulated biological categories were: RNA processing, protein metabolism, and cell growth. Within these categories we observed a down-regulation of fibroblast growth factor 2 (FGF2) (-1.5-fold) and aquaporin4 (AQP4) (-1.7-fold), alongside an up-regulation of fibroblast growth factor 9 (FGF9) (+1.7-fold) and vesicle associated membrane protein2 (VAMP2) (+1.7-fold). FGF2, FGF9, AQP4 and VAMP2 changes were confirmed at the protein level by immunohistochemistry. Alterations in FGF transcripts are in keeping with recent literature demonstrating such effects in patients with mood disorders.

Complementary patterns of gene expression by human oligodendrocyte progenitors and their environment predict determinants of progenitor maintenance and differentiation

OBJECTIVE

Glial progenitor cells are abundant in adult human white matter. This study was designed to identify signaling pathways regulating their self-renewal and fate.

METHODS

We compared the transcriptional profiles of freshly sorted adult human white matter progenitor cells (WMPCs), purified by A2B5-based immunomagnetic sorting, with those of the white matter from which they derived.

RESULTS

We identified 132 genes differentially expressed by WMPCs; these included principal components of five receptor-defined signaling pathways, represented by platelet derived growth factor receptor alpha (PDGFRA) and type 3 fibroblast growth factor receptor (FGFR3), receptor tyrosine phosphatase-beta/zeta (RTPZ), notch, and syndecan3. WMPCs also differentially expressed the bone morphogenetic protein 4 (BMP4) inhibitors neuralin and BAMBI (BMP and activin membrane-bound inhibitor), suggesting tonic defense against BMP signaling. Differential overexpression of RTPZ was accompanied by that of its modulators pleiotrophin, NrCAM, tenascin, and the chondroitin sulfate proteoglycans, suggesting the importance of RTPZ signaling to WMPCs. When exposed to the RTPZ inhibitor bpV(phen), or lentiviral-shRNAi against RTPZ, WMPCs differentiated as oligodendrocytes. Conversely, when neuralin and BAMBI were antagonized by BMP4, astrocytic differentiation was induced, which was reversible by noggin.

INTERPRETATION

The RTPZ and BMP pathways regulate the self-maintenance of adult human WMPCs, and can be modulated to induce their oligodendrocytic or astrocytic differentiation. As such, they provide targets by which to productively mobilize resident progenitor cells of the adult human brain.

Fibroblast growth factor 9: Cloning and immunolocalisation during tooth development in Didelphis albiventris

There are no reports in literature about functional roles of fibroblast growth factor 9 (FGF-9) in tooth development in animals with complete tooth pattern. The classical model for studying tooth development is the mouse, which has small number of teeth and distinctive incisor and molar patterns. The opossum Didelphis albiventris with five upper and four lower incisors, one canine, three premolars, and four molars, on each side of the jaw, seems to be a convenient model to test results obtained in the mouse. Molecular expression studies indicate that FGF-9 participates in murine tooth initiation and regulation of morphogenesis. Searching for similarities and differences in FGF-9 expression between the opossum and the mouse, amino acid sequence and expression pattern of FGF-9 in the developing first molars of D. albiventris were characterised. FGF-9 cDNA sequence was obtained using RT-PCR and expressed in bacterial system for recombinant protein production and analysis of immunoreactivity. FGF-9 expression during tooth development was investigated by immunoperoxidase method. FGF-9 protein consists in a 209-residue polypeptide with a predicted molecular mass of 23.5 kDa. FGF-9 amino acid sequence has 98% of sequence identity to human and 97% to rodents. During tooth development, epithelial FGF-9 expression was seen at the dental lamina stage. Mesenchymal expression was seen at the bud stage and at the cap stage. No significant expression was found in the enamel knot. While in rodents FGF-9 is involved in initiation and regulation of tooth shape, it is suggested that it is only involved in tooth initiation in D. albiventris.

Expression and possible function of fibroblast growth factor 9 (FGF9) and its cognate receptors FGFR2 and FGFR3 in postnatal and adult retina

Fibroblast growth factors (FGFs) are important regulators of retinal development and survival. We examined the expression and distribution of FGF9 and its preferred receptors FGFR2IIIc and FGFR3IIIc in this tissue. FGF9 transcripts in whole rat retina were detected by RT-PCR but were not present in purified cultured Muller glia. Transcripts appeared as 3.2-kb and 4.0-kb bands on Northern blots, and Western blotting of whole retina revealed FGF9-immunoreactive bands at 30 and 55 kDa. FGF9 mRNA demonstrated a biphasic expression profile, elevated at birth and adulthood, but relatively decreased during terminal retinal differentiation (4-14 days postnatal). Antibody labeling broadly reflected these findings: staining in vivo was observed mainly in the inner retina (and outer plexiform layer in adults) whereas FGF9 was not detectable in cultured Muller glia. In adults, FGF9 in situ hybridization also showed a detectable signal in inner retina. FGFR2IIIc and FGFR3IIIc were detected by RT-PCR, and Western blotting showed both FGFRs existed as multiple forms between approximately 100-200 kDa. FGFR2 and FGFR3 antibodies showed prominent labeling in the inner retina, especially in proliferating cultured Muller glia. Exogenous FGF9 elicited a dose-dependent increase in Muller glial proliferation in vitro. These data suggest a role for FGF9 in retinal differentiation and maturation, possibly representing a neuronally derived factor acting upon glial (and other) cells.

Cytosolic phospholipase A2 plays a key role in the pathogenesis of multiple sclerosis-like disease

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) that results in motor and sensory deficits. Although MS and its animal model, experimental autoimmune encephalomyelitis (EAE), are thought to be T cell-mediated diseases, the mechanisms underlying the lesions in the CNS are not fully understood. We propose that a strong candidate as a central mediator in evoking the complex pathological changes seen in MS and EAE is the enzyme cytosolic phospholipase A2 (cPLA2). One of the metabolic products of this enzyme is pro-inflammatory, while the other induces myelin breakdown, demyelination, and chemokine/cytokine expression. We provide evidence that cPLA2 is highly expressed in EAE lesions and show that blocking this enzyme leads to a remarkable reduction in the onset and progression of EAE.

Expression and synthesis of fibroblast growth factor-9 in human γδ T-lymphocytes. Response to isopentenyl pyrophosphate and TGF-β1/IL-15

Gammadelta T-lymphocytes are believed to play a role in maintaining the normal configuration of epithelial tissue. As little is known about the factors mediating this function, we addressed the question of whether gammadelta T-lymphocytes produce fibroblast growth factor (FGF)-9 as well as two other growth factors associated with epithelial tissue reconstitution. Blood gammadelta T cells isolated from healthy donors were grown in the presence of isopentenyl pyrophosphate (IPP) or transforming growth factor-beta1 (TGF-beta1)/interleukin-15 (IL-15) for 24 h and were assessed for the expression and synthesis of FGF-9, keratinocyte growth factor (KGF), and epidermal growth factor (EGF). Resting human gammadelta T cells constitutively expressed KGF and FGF-9 mRNA but no EGF mRNA. In the presence of IPP, FGF-9 mRNA expression significantly increased in a dose-dependent manner, expression of KGF remained unaltered, and EGF mRNA could not be detected. In contrast to IPP, stimulation of the cells with TGF-beta1/IL-15 did not alter FGF-9 expression. Moreover, stimulation with anti-CD3 does not induce FGF-9 expression but triggers a high signal of interferon-gamma mRNA. Western blot analysis of gammadelta T cell lysates, prepared 4 days following stimulation with IPP, showed an increase of FGF-9 protein as compared with control cells. In conclusion, the results demonstrate for the first time that human blood and bronchoalveolar lavage gammadelta T-lymphocytes are capable of expressing FGF-9. The data also provide novel evidence that immunoregulatory cells can synthesize FGF-9.

Angiogenesis and fibroblast growth factors (FGFs) in a three-dimensional collagen gel culture

Small pieces of mouse aorta were cultured in collagen gels, and the formation of capillary-like tubes from the aortic explant was observed under phase-contrast and transmission electron microscopes. Migration of fibroblastic cells from the aortic explant occurred in 2 days. After about 10 days of culture, capillary-like tubes from the aortic explant were formed in the collagen gels. An immunohistochemical study on the collagen gel culture revealed the expression of fibroblast growth factor 2 (FGF-2) near the aortic explant at the active initial stage, with random migration of fibroblastic cells expressing FGF-9. mRNA was isolated from these cultures, and reverse transcription-polymerase chain reaction (RT-PCR) of the cultures revealed the expressions of both FGF-2 and FGF-9. Based on our results, we propose that FGF-9 is also related to angiogenic events.

Human RPE cells express the FGFR2IIIc and FGFR3IIIc splice variants and FGF9 as a potential high affinity ligand

The expression of splice variants of FGF receptors, which differ in the third Ig domain, was investigated in retinal pigment epithelium (RPE) cells in vitro and in vivo. This region of the protein determines ligand-binding specificity. Additionally, the expression of potential ligands for these receptors was investigated. Expression of FGF receptor transcript alternative splicing was analyzed by RT-PCR/Southern analysis in RPE cells in vitro and in vivo. The expression of FGFs by RT-PCR, in situ hybridization, and immunohistochemistry in sections of the human posterior pole was also investigated. The ARPE-19 cell line expresses only the FGFR2IIIc splice variant and does not express any FGFR3 splice variants in vitro. Two in vivo samples exhibited expression of the FGFR2IIIc and FGFR3IIIc splice variants and no evidence of the corresponding IIIb splice variant. The results from previous studies for these receptors imply that FGF9 or FGF4 could act as ligands. We demonstrated that FGF9 is expressed in a subpopulation of the RPE, as well as photoreceptors and other neurons of the retina. FGF4 was not detected by RT-PCR analysis in RPE cells in vitro. These data suggest that FGF9 may be an autocrine/paracrine factor in the outer retina.

FGF-18 is a neuron-derived glial cell growth factor expressed in the rat brain during early postnatal development

We examined the expression of fibroblast growth factor-18 (FGF-18) in the rat brain during postnatal development by in situ hybridization. FGF-18 was transiently expressed at the early postnatal stages in various regions of the rat brain including the cerebral cortex and hippocampus. FGF-18 in the brain was preferentially expressed in neurons but not in glial cells. To elucidate the role of FGF-18 in the brain, we examined the ligand-specificity of FGF-18 by the BIAcore system. FGF-18 was found to bind to FGF receptors (FGFRs)-3c and -2c but not to FGFR-1c, suggesting that FGF-18 acts on glial cells but not on neurons. Therefore, we examined the mitogenic activity of FGF-18 for cultured rat astrocytes and microglia. FGF-18 was found to have mitogenic activity for both astrocytes and microglia. We also examined the neurotrophic activity of FGF-18 for cultured rat cortical neurons. FGF-18 was found to have no neurotrophic activity. The present findings indicated that FGF-18 is a unique FGF that plays a role as a neuron-derived glial cell growth factor in early postnatal development when gliogenesis occurs.

Oligodendrocytes as providers of growth factors

Glial cells recently are being appreciated as supporters of brain neurons. This review addresses their role as growth factor providers. While the function of astrocytes in this capacity is known, new data indicate that oligodendrocytes, the myelinating cells of the brain, exhibit similar abilities. Oligodendrocytes provide trophic signals to nearby neurons and synthesize defined growth factors. Expression of growth factors is influenced by neural signals. The review summarizes these roles and their implications in brain function.

Fibroblast growth factors in the developing central nervous system

1. It is now clear that members of the fibroblast growth factor (FGF) family have multiple roles during the formation of the central nervous system (CNS). 2. There are at least 23 members of the FGF family and, of these, 10 are expressed in the developing CNS, along with four FGF receptors (FGFR-1-4). 3. The present review discusses the roles of these FGFs, with emphasis on FGF-2, FGF-8, FGF-15 and FGF-17. Fibroblast growth factors-2 and -15 are generally expressed throughout the developing CNS, whereas FGF-8 and FGF-17 are tightly localized to specific regions of the developing brain and are only expressed in the embryo during the early phases of proliferation and neurogenesis. 4. Expression studies on FGFRs in the chick and mouse indicate that FGFR-1 is most generally expressed, whereas FGFR-2 and FGFR-3 show highly localized but changing patterns of expression throughout CNS development. The FGFR-4 has been localized to the developing CNS in fish but not at a detailed level, as yet, in chick or mouse. 5. A picture is emerging from these studies that particular FGFs signal through specific receptors in a highly localized manner to regulate the development of different regions of the brain. 6. This picture has been demonstrated so far for the developing cortex (FGF-2-/- mice), the forebrain and midbrain (FGF-8 hypomorphs) and the cerebellum (FGF-17/FGF-8 mutant mice). In addition, generation of mutant animals deleted for FGFR-1 and FGFR-2b IIIb demonstrate their importance in FGF signalling. 7. However, there are significant gaps in our knowledge of the localization of members of the FGF family and their receptors. More detailed information on the spatio-temporal mapping of FGFs and FGFR isoforms is required in order to understand the molecular mechanisms through which FGFs signal.

Crystal structure of fibroblast growth factor 9 reveals regions implicated in dimerization and autoinhibition

Fibroblast growth factors (FGFs) constitute a large family of heparin-binding growth factors with diverse biological activities. FGF9 was originally described as glia-activating factor and is expressed in the nervous system as a potent mitogen for glia cells. Unlike most FGFs, FGF9 forms dimers in solution with a K(d) of 680 nm. To elucidate the molecular mechanism of FGF9 dimerization, the crystal structure of FGF9 was determined at 2.2 A resolution. FGF9 adopts a beta-trefoil fold similar to other FGFs. However, unlike other FGFs, the N- and C-terminal regions outside the beta-trefoil core in FGF9 are ordered and involved in the formation of a 2-fold crystallographic dimer. A significant surface area (>2000 A(2)) is buried in the dimer interface that occludes a major receptor binding site of FGF9. Thus, we propose an autoinhibitory mechanism for FGF9 that is dependent on sequences outside of the beta-trefoil core. Moreover, a model is presented providing a molecular basis for the preferential affinity of FGF9 toward FGFR3.

Self-secretion of fibroblast growth factor-9 supports basal forebrain cholinergic neurons in an autocrine/paracrine manner

We examined the effect of fibroblast growth factor (FGF)-9 on primary cultures of rat basal forebrain cholinergic neurons (BFCN) obtained at embryonic day 17. FGF-9 enhanced survival of AChE-positive neurons, increased their mean soma size, and up-regulated their choline acetyltransferase (ChAT) activity. The ChAT-promoting effect of FGF-9 was approximately as potent as that of nerve growth factor (NGF) and was greater than those of basic fibroblast growth factor (bFGF), ciliary neurotrophic factor (CNTF), or glia-derived neurotrophic factor (GDNF). Simultaneous addition of FGF-9 and NGF induced extremely high ChAT levels, suggesting that FGF-9 and NGF may enhance cholinergic properties in BFCN via different pathways that can act synergistically. In immunocytochemical and in situ hybridization studies in cultured cells and also in sections of adult rat brain, BFCN showed cytoplasmic immunostaining for FGF-9 and expressed FGF-9 messenger RNA; thus, we concluded that FGF-9 acts on BFCN in an autocrine and/or paracrine manner. Although effective delivery of exogenous FGF-9 into the central nervous system remains a problem to be solved, FGF-9 may be a promising candidate for therapeutic trials in Alzheimer disease.

Fibroblast growth factor-9 modulates the expression of myelin related proteins and multiple fibroblast growth factor receptors in developing oligodendrocytes

The effect of fibroblast growth factor (FGF)-9 on the expression of FGF receptors (FGFR) and the major myelin proteins was examined in cultures of developing rat brain oligodendrocytes (OLs), using immunological techniques. FGFR-1, -3, and -4 were expressed at all developmental stages but were not present in isolated myelin fractions. By contrast, FGFR-2 protein was predominantly localized to differentiating cells and myelin. FGF-9 altered FGFR and myelin protein levels during OL differentiation; there was increased expression of FGFR-1 and decreased levels of both FGFR-2 and myelin proteins. Further, FGF-9 stimulated mitogen-associated protein kinase (MAPK) phosphorylation. The effect of FGF-9 on MAPK, however, was transient and less robust in progenitor cells than in differentiated oligodendrocytes. The effects of FGF-9 and FGF-2 on FGFR and myelin protein levels were comparable; both up-regulated FGFR-1, and down-regulated FGFR-2, CNP, PLP and MBP. These findings suggest that FGF-9 may be important for glial cell development.

Skeletal dysplasia and defective chondrocyte differentiation by targeted overexpression of fibroblast growth factor 9 in transgenic mice

Mutations in fibroblast growth factor receptor 3 (FGFR3) cause several human chondrodysplasias, including achondroplasia, the most common form of dwarfism in humans. From in vitro studies, the skeletal defects observed in these disorders have been attributed to constitutive activation of FGFR3. Here we show that FGF9 and FGFR3, a high-affinity receptor for this ligand, have similar developmental expression patterns, particularly in areas of active chondrogenesis. Targeted overexpression of FGF9 to cartilage of transgenic mice disturbs postnatal skeletal development and linear bone growth. The growth plate of these mice exhibits reduced proliferation and terminal differentiation of chondrocytes similar to that observed in the human disorders. The observations provide evidence that targeted, in vivo activation of endogenous FGFR3 inhibits bone growth and demonstrate that signals derived from FGF9-FGFR3 interactions can physiologically block endochondral ossification to produce a phenotype characteristic of the achondroplasia group of human chondrodysplasias.

A hydrophobic region locating at the center of fibroblast growth factor-9 is crucial for its secretion

Fibroblast growth factor (FGF)-9 is a glycosylated neurotrophic polypeptide highly expressed in brain. The mechanism for its secretion from expressing cells is unclear, because its primary structure lacks a cleavable signal sequence. We, therefore, investigated the mechanism and structural requirements for secretion of FGF-9. As with other secreted proteins, in vitro translation of FGF-9 was inhibited by signal recognition particle, which binds to the signal sequence. When translated in vitro, full-length FGF-9 was translocated into microsomes, glycosylated, and protected from trypsin digestion. By using various FGF-9 deletion mutants, we found that two hydrophobic domains, located at the N terminus and at the center of the FGF-9 primary structure, were crucial for translocation. Examination of various point mutants revealed that local hydrophobicity of the central hydrophobic domain, but not the N terminus, was crucial for translocation. Analogous results were obtained with respect to FGF-9 secretion from transfectant cells. Upon deletion of the complete sequence preceding it, the previously uncleavable hydrophobic domain appeared to serve as a cleavable signal sequence. Our results suggest that nascent FGF-9 polypeptides translocate into endoplasmic reticulum without peptide cleavage via a co-translational pathway in which both the N terminus and the central hydrophobic domain are important; thereafter, FGF-9 is glycosylated and secreted.

Genomic organization and embryonic expression of the mouse fibroblast growth factor 9 gene

Fibroblast growth factor 9 (FGF9), originally cloned as glial-activating factor from human glioma cells, is expressed in adult rat brain and kidney. Here we report the chromosomal localization, genomic organization, and embryonic expression pattern of the mouse Fgf9 gene. Fgf9 maps to chromosome 14 near the Ctla6 locus. The gene spans more than 34 kb and contains three exons and two introns. Translation initiation occurs in exon 1, and translation termination occurs in exon 3. Fgf9 RNA was detected during mouse embryogenesis in several tissues in which Fgf gene expression has not been previously described, including intermediate mesoderm of late-stage gastrulation, ventricular myocardium, lung pleura, skeletal myoblasts in the early limb bud, spinal cord motor neurons, olfactory bulb, and gut lumenal epithelium. Fgf9 is coexpressed with other Fgf genes in some skeletal myoblasts, in limb apical ectoderm, in craniofacial ectoderm, and in the retina, inner ear, and tooth bud. Dev Dyn 1999;216:72-88.

Characterization of a novel member of the FGF family, XFGF-20, in Xenopus laevis

The cDNA for a novel member of the FGF family (XFGF-20) was isolated from a Xenopus cDNA library prepared at the tailbud stage using as a probe the product of degenerate PCR performed with primers based on mammalian FGF-9s. This cDNA was 1860 bp long, and contained a single open reading frame that encoded 208 amino acid residues. The deduced amino acid sequence contained a motif characteristic of the FGF family and it was similar (73.1% overall homology) to XFGF-9 but differed from XFGF-9 in its amino-terminal region (33.3% homology). XFGF-20 mRNA was expressed only zygotically in embryos at and after the blastula stage, but it was also specifically expressed in the stomach and testis of adults. By contrast, XFGF-9 mRNA was expressed maternally in eggs and in many adult tissues. When XFGF-20 mRNA was overexpressed in early embryos, gastrulation was abnormal and development of anterior structures was suppressed. In such embryos, the expression of the Xbra transcript was suppressed during gastrulation while the expression of the transcripts of cerberus, Siamois, dkk-1, chordin, and Xotx-2 genes was normal. These results suggest that correct expression of XFGF-20 during gastrulation is required for the formation of normal head structures in Xenopus laevis during embryogenesis and that expression of the Xbra gene mediates this phenomenon.

FGF-9 is an autocrine/paracrine neurotrophic substance for spinal motoneurons

Motoneurons need muscle-derived neurotrophic substances for their survival during the initial phase of their development, but after maturation they lose this requirement and can survive after axotomy. This suggests that some neurotrophic substances other than target-derived ones control the survival of motoneurons in adults. Because spinal motoneurons express fibroblast growth factor-9 (FGF-9) messenger RNA, we hypothesized that FGF-9 might be an autocrine or paracrine survival factor for motoneurons. FGF-9 promoted the survival of motoneurons and upregulated the choline acetyl-transferase (ChAT) activity in the dissociated cultures of ventral half of rat E13 spinal cord. Externally added FGF-9 was more effective in low density cultures, and polyclonal blocking antibody against FGF-9 significantly lowered the ChAT activity. Our results support an autocrine or paracrine role for FGF-9 in mediating the survival of spinal motoneurons. Non-target-derived neurotrophic substances for motoneurons including FGF-9 should be important in the pathogenesis of motor neuron disorders in the adults, especially amyotrophic lateral sclerosis.

Recombinant rat fibroblast growth factor-16: structure and biological activity

Fibroblast growth factor-16 (FGF-16) is the most recent member of the FGF family to be cloned. Since the biologic activity of rat FGF-16 (rFGF-16) was unknown, and this protein has no apparent signal sequence, we transformed its entire cDNA into Escherichia coli for high-level expression and further characterization of this novel protein. An attempt was made to purify the expressed protein from the supernatant of mechanically lysed cells using sequential cation-exchange chromatography. This resulted in a gradual loss of the protein as precipitate throughout the purification process. In addition to precipitation during purification, sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the partially purified materials showed a cluster of protein bands around 20k to 29k. Sequence analysis of the major bands indicated that two N-terminal truncations had occurred, during E. coli fermentation, purification, or both. The largest truncation resulted in the removal of the 34 N-terminal amino acids, including the initiation codon methionine. We cloned d34 rFGF-16, expressed the gene in E. coli, and developed a purification process for this form. Even with this truncated form, precipitation was a problem. We were largely able to overcome this problem, however, by including EDTA throughout the purification process. We have characterized the structure of purified d34 rFGF-16 extensively using circular dichroism, Fourier transform infrared spectroscopy, and sedimentation velocity analysis. These studies revealed that the protein has a distinct tertiary structure, consists primarily of beta-strands, has a weak tendency to self-associate, and is fairly extended. We then performed biologic assays which showed that d34 rFGF-16 induces oligodendrocyte proliferation in vitro, and induces hepatocellular proliferation and increased liver weight in vivo. In summary, FGF-16, a novel FGF family member, has both unique structural and biological properties.

Fibroblast growth factor (FGF)-9 immunoreactivity in senile plaques

We examined fibroblast growth factor (FGF)-9 immunoreactivity in human hippocampal sections of Alzheimer's disease (AD). FGF-9 immunoreactivity was observed in dystrophic neurites of senile plaques in AD and control cases, in addition to the hippocampal and cortical neurons. The amyloid core and neurofibrillary tangles lacked immunoreactivity. FGF-9 immunoreactive astrocytes were conspicuous in AD brains. FGF-9 may be involved in the neuropathology of AD.

Overlapping effects of different members of the FGF family on lens fiber differentiation in transgenic mice

Fibroblast growth factors (FGFs), such as FGF-1, have been shown to induce differentiation of lens epithelial cells both in tissue culture and in transgenic mice. In the present study, using the alpha A-crystallin promoter, we generated transgenic mice that express different FGFs (FGF-4, FGF-7, FGF-8, FGF-9) specifically in the lens. All four FGFs induced changes in ocular development. Microphthalmic eyes were evident in transgenic mice expressing FGF-8, FGF-9 and some lines expressing FGF-4. A developmental study of the microphthalmic eyes revealed that, by embryonic day 15, expression of these FGFs induced lens epithelial cells to undergo premature fiber differentiation. In less severely affected lines expressing FGF-4 or FGF-7, the lens epithelial cells exhibited a premature exit from the cell cycle and underwent a fiber differentiation response later in development, leading to cataract formation. The responsiveness of lens cells to different FGFs indicates that these proteins stimulate the same or overlapping downstream signalling pathway(s). These overlapping effects of different FGFs on a common cell type indicate that the normal developmental roles for these genes are determined by the temporal and spatial regulation of their expression patterns. The fact that any of these FGFs can induce ocular defects and loss of lens transparency implies that it is essential for the normal eye to maintain very specific spatial control over FGF expression in order to prevent cataract induction.