RESUMEN
Fibroblast Growth Factor 6 (FGF6), also referred to as HST2 or HBGF6, is a member of the Fibroblast Growth Factor (FGF), the Heparin Binding Growth Factor (HBGF) and the Heparin Binding Secretory Transforming Gene (HST) families. The genomic and protein structure of FGF6 is highly conserved among varied species, as is its expression in muscle and muscle progenitor cells. Like other members of the FGF family, FGF6 regulates cell proliferation, differentiation, and migration. Specifically, it plays key roles in myogenesis and muscular regeneration, angiogenesis, along with iron transport and lipid metabolism. Similar to others from the FGF family, FGF6 also possesses oncogenic transforming activity, and as such is implicated in a variety of cancers.
Asunto(s)
Diferenciación Celular , Factor 6 de Crecimiento de Fibroblastos , Humanos , Animales , Diferenciación Celular/genética , Factor 6 de Crecimiento de Fibroblastos/genética , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Desarrollo de Músculos/genética , Proliferación Celular/genética , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patología , Movimiento Celular/genéticaRESUMEN
The de novo differentiation of hyperplastic adipocytes from adipocyte progenitor cells (APCs) is accompanied by a reduction in adipose tissue fibrosis and inflammation and improvement in insulin sensitivity in obesity and aging. However, the regulators of APC proliferation are poorly understood. Here, we show that fibroblast growth factor 6 (FGF6) acts in an autocrine and/or paracrine manner to control platelet-derived growth factor receptor α-positive APC proliferation via extracellular signal-regulated kinase (ERK) signaling. Specific FGF6 overexpression in inguinal white adipose tissue (iWAT) improved the signs of high-fat diet- or aging-induced adipose hypertrophy and insulin resistance. Conversely, chronic FGF6 expression blockade in iWAT, mediated by a neutralizing antibody or Fgf6 expression deficiency, impaired adipose tissue expansion and glucose tolerance. Overall, our data suggest that FGF6 acts as a proliferative factor for APCs to maintain fat homeostasis and insulin sensitivity.
Asunto(s)
Resistencia a la Insulina , Neoplasias , Animales , Ratones , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Tejido Adiposo/metabolismo , Adipocitos/metabolismo , Tejido Adiposo Blanco/metabolismo , Obesidad/metabolismo , Neoplasias/metabolismo , Proliferación Celular , Homeostasis , Dieta Alta en Grasa , Ratones Endogámicos C57BLRESUMEN
OBJECTIVES: Myocardial infarction (MI) commonly occurs in patients with coronary artery disease and have high mortality. Current clinical strategies for MI still limited to reducing the death of myocardial cells but failed to replace these cells. This study aimed to investigate the role of fibroblast growth factor 6 (FGF6) in enhancing the proliferative potential of cardiomyocytes (CMs) after ischemic injury via the Hippo pathway. MATERIALS AND METHODS: Expression of FGF6 protein was analysed in mice with MI induced by ligation of the left anterior descending coronary artery. Activation of the Hippo pathway and the proliferation potential were examined in ischemic CMs, treated with FGF6 protein or transfected with an adeno-virus carrying FGF6 sh-RNA. Immunofluorescence staining and western blotting were performed to assess the relationship between FGF6 and the Hippo pathway. RESULTS: We found that FGF6 expression was significantly increased in the MI mouse model. Knockdown of FGF6 synthesis resulted in poorer heart function after MI. By contrast, treatment with recombinant human FGF6 protein improved heart function, reduced infarct size, and promoted cardiac repair. Additionally, FGF6 restrains the activation of the Hippo pathway and subsequently promotes nuclear accumulation of YAP. This was largely counteracted by treatment with extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor U0126. CONCLUSION: FGF6 inhibits the Hippo pathway via ERK1/2, and facilitates nuclear translocation of YAP, and thereby promotes cardiac repair after MI.
Asunto(s)
Vía de Señalización Hippo , Infarto del Miocardio , Animales , Modelos Animales de Enfermedad , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Humanos , Ratones , Infarto del Miocardio/terapia , Miocitos CardíacosRESUMEN
Skeletal muscle stem cells, i.e., satellite cells (SCs), are the essential source of new myonuclei for skeletal muscle regeneration following injury or chronic degenerative myopathies. Both SC number and regenerative capacity diminish during aging. However, molecular regulators that govern sizing of the initial SC pool are unknown. We demonstrate that fibroblast growth factor 6 (FGF6) is critical for SC pool scaling. Mice lacking FGF6 have reduced SCs of early postnatal origin and impaired regeneration. By contrast, increasing FGF6 during the early postnatal period is sufficient for SC expansion. Together, these data support that FGF6 is necessary and sufficient to modulate SC numbers during a critical postnatal period to establish the quiescent adult muscle stem cell pool. Our work highlights postnatal development as a time window receptive for scaling a somatic stem cell population via growth factor signaling, which might be relevant for designing new biomedical strategies to enhance tissue regeneration.
Asunto(s)
Factor 6 de Crecimiento de Fibroblastos/metabolismo , Músculo Esquelético/patología , Células Madre/patología , Animales , Animales Recién Nacidos , Proliferación Celular , Ratones Endogámicos C57BL , Ratones Mutantes , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/lesiones , RegeneraciónRESUMEN
BACKGROUND: Bladder cancer (BCa) is a common genitourinary malignancy with higher incidence in males. Long intergenic non-protein coding RNA 265 (LINC00265) is identified as an oncogene in many malignancies, while its role in BCa development remains unknown. PURPOSE: To explore the functions and mechanism of LINC00265 in BCa. RESEARCH DESIGN: Reverse transcription quantitative polymerase chain reaction was performed to examine LINC00265 expression in BCa cells. Cell counting kit-8 assays, colony formation assays, TdT-mediated dUTP Nick-End Labeling assays, and Transwell assays were conducted to examine BCa cell viability, proliferation, apoptosis, and migration. Luciferase reporter assays and RNA immunoprecipitation assays were carried out to explore the binding capacity between miR-4677-3p and messenger RNA fibroblast growth factor 6 (FGF6) (or LINC00265). Xenograft tumor model was established to explore the role of LINC00265 in vivo. RESULTS: LINC00265 was highly expressed in BCa cells. LINC00265 knockdown inhibited xenograft tumor growth and BCa cell viability, proliferation and migration while enhancing cell apoptosis. Moreover, LINC00265 interacted with miR-4677-3p to upregulate the expression of FGF6. FGF6 overexpression reversed the suppressive effect of LINC00265 knockdown on malignant phenotypes of BCa cells. CONCLUSIONS: LINC00265 promotes the viability, proliferation, and migration of BCa cells by binding with miR-4677-3p to upregulate FGF6 expression.
Asunto(s)
Supervivencia Celular , Factor 6 de Crecimiento de Fibroblastos , Regulación Neoplásica de la Expresión Génica , ARN Largo no Codificante , Animales , Humanos , Masculino , Ratones , Línea Celular Tumoral , Movimiento Celular , Proliferación Celular , Supervivencia Celular/fisiología , Factor 6 de Crecimiento de Fibroblastos/genética , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Regulación Neoplásica de la Expresión Génica/fisiología , Ratones Desnudos , Neoplasias Experimentales , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismoRESUMEN
Obesity, a major health care issue, is characterized by metabolic abnormalities in multiple tissues, including the skeletal muscle. Although dysregulation of skeletal muscle metabolism can strongly influence the homeostasis of systemic energy, the underlying mechanism remains unclear. We found promoter hypermethylation and decreased gene expression of fibroblast growth factor 6 (FGF6) in the skeletal muscle of individuals with obesity using high-throughput sequencing. Reduced binding of the cyclic AMP responsive element binding protein-1 (CREB1) to the hypermethylated cyclic AMP response element, which is a regulatory element upstream of the transcription initiation site, partially contributed to the downregulation of FGF6 in patients with obesity. Overexpression of Fgf6 in mouse skeletal muscle stimulated protein synthesis, activating the mammalian target of rapamycin pathway, and prevented the increase in weight and the development of insulin resistance in high-fat diet-fed mice. Thus, our findings highlight the role played by Fgf6 in regulating skeletal muscle hypertrophy and whole-body metabolism, indicating its potential in strategies aimed at preventing and treating metabolic diseases.
Asunto(s)
Factor 6 de Crecimiento de Fibroblastos/genética , Resistencia a la Insulina/genética , Músculo Esquelético/metabolismo , Obesidad/genética , Adulto , Animales , Dieta Alta en Grasa , Regulación hacia Abajo , Femenino , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Técnicas de Sustitución del Gen , Humanos , Masculino , Ratones , Persona de Mediana Edad , Obesidad/metabolismoRESUMEN
Uncoupling protein-1 (UCP1) plays a central role in energy dissipation in brown adipose tissue (BAT). Using high-throughput library screening of secreted peptides, we identify two fibroblast growth factors (FGF), FGF6 and FGF9, as potent inducers of UCP1 expression in adipocytes and preadipocytes. Surprisingly, this occurs through a mechanism independent of adipogenesis and involves FGF receptor-3 (FGFR3), prostaglandin-E2 and interaction between estrogen receptor-related alpha, flightless-1 (FLII) and leucine-rich-repeat-(in FLII)-interacting-protein-1 as a regulatory complex for UCP1 transcription. Physiologically, FGF6/9 expression in adipose is upregulated by exercise and cold in mice, and FGF9/FGFR3 expression in human neck fat is significantly associated with UCP1 expression. Loss of FGF9 impairs BAT thermogenesis. In vivo administration of FGF9 increases UCP1 expression and thermogenic capacity. Thus, FGF6 and FGF9 are adipokines that can regulate UCP1 through a transcriptional network that is dissociated from brown adipogenesis, and act to modulate systemic energy metabolism.
Asunto(s)
Adipocitos Marrones/metabolismo , Adipogénesis , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Factor 9 de Crecimiento de Fibroblastos/metabolismo , Obesidad/metabolismo , Proteína Desacopladora 1/metabolismo , Adipocitos Marrones/citología , Tejido Adiposo Pardo/citología , Tejido Adiposo Pardo/metabolismo , Animales , Factor 6 de Crecimiento de Fibroblastos/genética , Factor 9 de Crecimiento de Fibroblastos/genética , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Obesidad/genética , Obesidad/fisiopatología , Termogénesis , Proteína Desacopladora 1/genéticaRESUMEN
BACKGROUND: Severe peripheral nerve injury leads to skeletal muscle atrophy and impaired limb function that is not sufficiently improved by existing treatments. Fibroblast growth factor 6 (FGF6) is involved in tissue regeneration and is dysregulated in denervated rat muscles. However, the way that FGF6 affects skeletal muscle repair after peripheral nerve injury has not been fully elucidated. METHODS: In this study, we investigated the role of FGF6 in the regeneration of denervated muscles using myoblast cells and an in vivo model of peripheral nerve injury. RESULTS: FGF6 promoted the viability and migration of C2C12 and primary myoblasts in a dose-dependent manner through FGFR1-mediated upregulation of cyclin D1. Low concentrations of FGF6 promoted myoblast differentiation through FGFR4-mediated activation of ERK1/2, which upregulated expression of MyHC, MyoD, and myogenin. FGFR-1, FGFR4, MyoD, and myogenin were not upregulated when FGF6 expression was inhibited in myoblasts by shRNA-mediated knockdown. Injection of FGF6 into denervated rat muscles enhanced the MyHC-IIb muscle fiber phenotype and prevented muscular atrophy. CONCLUSION: These findings indicate that FGF6 reduces skeletal muscle atrophy by relying on the ERK1/2 mechanism and enhances the conversion of slow muscle to fast muscle fibers, thereby promoting functional recovery of regenerated skeletal muscle after innervation.
Asunto(s)
Factor 6 de Crecimiento de Fibroblastos/genética , Proteína Quinasa 1 Activada por Mitógenos/genética , Proteína Quinasa 3 Activada por Mitógenos/genética , Músculo Esquelético/metabolismo , Traumatismos de los Nervios Periféricos/genética , Receptor Tipo 1 de Factor de Crecimiento de Fibroblastos/genética , Regeneración/genética , Animales , Diferenciación Celular , Línea Celular , Movimiento Celular , Proliferación Celular , Ciclina D1/genética , Ciclina D1/metabolismo , Factor 6 de Crecimiento de Fibroblastos/antagonistas & inhibidores , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Regulación de la Expresión Génica , Masculino , Proteína Quinasa 1 Activada por Mitógenos/metabolismo , Proteína Quinasa 3 Activada por Mitógenos/metabolismo , Desnervación Muscular/métodos , Músculo Esquelético/inervación , Músculo Esquelético/patología , Proteína MioD/genética , Proteína MioD/metabolismo , Mioblastos/metabolismo , Mioblastos/patología , Miogenina/genética , Miogenina/metabolismo , Cadenas Pesadas de Miosina/genética , Cadenas Pesadas de Miosina/metabolismo , Traumatismos de los Nervios Periféricos/metabolismo , Traumatismos de los Nervios Periféricos/patología , Cultivo Primario de Células , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Ratas , Ratas Sprague-Dawley , Receptor Tipo 1 de Factor de Crecimiento de Fibroblastos/metabolismo , Receptor Tipo 4 de Factor de Crecimiento de Fibroblastos/genética , Receptor Tipo 4 de Factor de Crecimiento de Fibroblastos/metabolismo , Nervio Ciático/lesionesRESUMEN
The present study was conducted to investigate the regulative function of FGF6 in the muscle growth of grass carp (Ctenopharyngodon idellus) by the bioinformatics analysis and expression pattern analyses of FGF6 genes in different developmental stages and tissues, as well as the correlation analysis between muscle growth and FGF6 expression after fish were fed with different levels of dietary lotus leaf flavonoids (LLF) (0, 0.03%, 0.06%, 0.09%). Results showed that the FGF6a and FGF6b genes are two homologs of the FGF6 family, encoding 205 and 209 amino acids, respectively. Alignment of amino acid sequences and phylogenetic analysis demonstrated that FGF6a and FGF6b are highly conserved with other vertebrates. Quantitative RT-PCR analysis showed both FGF6a and FGF6b expressions were high in brain and muscle but low in other examined tissues. During embryonic development, FGF6a and FGF6b mRNA expressions could be detected as early as at fertilized egg stage and displayed the highest value at cleavage stage. Dietary LLF affected the gene expression of FGF6 in white muscle. The relative expression of FGF6a of 0.06% LLF group was significantly higher than that of 0.09% LLF group, while FGF6b expression of 0.06% LLF group was higher than those of other groups (P < 0.05). The muscle fiber diameter was significantly higher in 0.06% LLF group in comparison with other groups, while the fiber density in this group was lower (P < 0.05). Both FGF6a and FGF6b expressions were positively correlated with fiber diameter but negatively correlated with fiber density. These results collectively suggest that FGF6a and FGF6b play an important role in muscle growth regulation in grass carp.
Asunto(s)
Carpas/crecimiento & desarrollo , Carpas/metabolismo , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Regulación del Desarrollo de la Expresión Génica/fisiología , Músculo Esquelético/crecimiento & desarrollo , Secuencia de Aminoácidos , Animales , Carpas/embriología , Factor 6 de Crecimiento de Fibroblastos/genética , Flavonoides/química , Flavonoides/farmacología , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Larva , Lotus/química , Modelos Moleculares , Filogenia , Extractos Vegetales/química , Hojas de la Planta/química , Conformación Proteica , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
Standard analyses applied to genome-wide association data are well designed to detect additive effects of moderate strength. However, the power for standard genome-wide association study (GWAS) analyses to identify effects from recessive diplotypes is not typically high. We proposed and conducted a gene-based compound heterozygosity test to reveal additional genes underlying complex diseases. With this approach applied to iron overload, a strong association signal was identified between the fibroblast growth factor-encoding gene, FGF6, and hemochromatosis in the central Wisconsin population. Functional validation showed that fibroblast growth factor 6 protein (FGF-6) regulates iron homeostasis and induces transcriptional regulation of hepcidin. Moreover, specific identified FGF6 variants differentially impact iron metabolism. In addition, FGF6 downregulation correlated with iron-metabolism dysfunction in systemic sclerosis and cancer cells. Using the recessive diplotype approach revealed a novel susceptibility hemochromatosis gene and has extended our understanding of the mechanisms involved in iron metabolism.
Asunto(s)
Exoma/genética , Factor 6 de Crecimiento de Fibroblastos/genética , Regulación de la Expresión Génica , Predisposición Genética a la Enfermedad , Hemocromatosis/patología , Hepcidinas/metabolismo , Sobrecarga de Hierro/patología , Hierro/metabolismo , Secuencia de Aminoácidos , Estudios de Casos y Controles , Diploidia , Femenino , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Estudios de Seguimiento , Genes Recesivos , Estudio de Asociación del Genoma Completo , Hemocromatosis/genética , Hepcidinas/genética , Humanos , Sobrecarga de Hierro/genética , Masculino , Persona de Mediana Edad , Neoplasias/genética , Neoplasias/patología , Mapas de Interacción de Proteínas , Esclerodermia Sistémica/genética , Esclerodermia Sistémica/patología , Homología de SecuenciaRESUMEN
The long term effects of fish oil (FO) substitution by increasing the levels of vegetable oils (VO), 0% (CTR), 50% (VO50) and 100% (VO100), in diets for Senegalese sole were evaluated in terms of skeletal muscle cellularity and expression of related genes. After 140 days of feeding, all fish had similar body weight and length. The inclusion of 50% VO did not result in differences in muscle cellularity, but dorsal muscle cross-sectional area and fast-twitch fibre diameter increased in fish fed total FO substitution, whilst fibre density was reduced (P < 0.05) in relation to CTR. The total number of fibres was similar in all treatments. FO substitution did not affect the transcript levels of myogenic genes (myf5, mrf4, myog, myod1, myod2), but resulted in a two-fold increase of fgf6 transcript levels compared to CTR (P < 0.05). The relative expression of igf-I was higher in VO100 than in VO50, but was similar to CTR. FO substitution resulted in cellularity changes related to the stimulation of muscle hypertrophic growth, but not hyperplastic growth, and associated with a nutritional modulation of fgf6 by dietary VO. This study indicates that 50% VO does not affect the muscle phenotype, but total FO substitution stimulates muscle hypertrophy.
Asunto(s)
Alimentación Animal/análisis , Factor 6 de Crecimiento de Fibroblastos/genética , Aceites de Pescado/metabolismo , Proteínas de Peces/genética , Peces Planos/crecimiento & desarrollo , Músculos/metabolismo , Aceites de Plantas/metabolismo , Animales , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Proteínas de Peces/metabolismo , Peces Planos/genética , Peces Planos/metabolismo , Desarrollo de Músculos , Regulación hacia ArribaRESUMEN
The development of the craniofacial muscles requires reciprocal interactions with surrounding craniofacial tissues that originate from cranial neural crest cells (CNCCs). However, the molecular mechanism involved in the tissue-tissue interactions between CNCCs and muscle progenitors during craniofacial muscle development is largely unknown. In the current study, we address how CNCCs regulate the development of the tongue and other craniofacial muscles using Wnt1-Cre; Alk5(fl/fl) mice, in which loss of Alk5 in CNCCs results in severely disrupted muscle formation. We found that Bmp4 is responsible for reduced proliferation of the myogenic progenitor cells in Wnt1-Cre; Alk5(fl/fl) mice during early myogenesis. In addition, Fgf4 and Fgf6 ligands were reduced in Wnt1-Cre; Alk5(fl/fl) mice and are critical for differentiation of the myogenic cells. Addition of Bmp4 or Fgf ligands rescues the proliferation and differentiation defects in the craniofacial muscles of Alk5 mutant mice in vitro. Taken together, our results indicate that CNCCs play critical roles in controlling craniofacial myogenic proliferation and differentiation through tissue-tissue interactions.
Asunto(s)
Músculos Faciales/embriología , Desarrollo de Músculos/genética , Cresta Neural/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Receptores de Factores de Crecimiento Transformadores beta/genética , Animales , Apoptosis/genética , Proteína Morfogenética Ósea 4/biosíntesis , Proteína Morfogenética Ósea 4/genética , Proteína Morfogenética Ósea 4/metabolismo , Diferenciación Celular/genética , Proliferación Celular , Células Cultivadas , Factor 4 de Crecimiento de Fibroblastos/biosíntesis , Factor 4 de Crecimiento de Fibroblastos/genética , Factor 4 de Crecimiento de Fibroblastos/metabolismo , Factor 6 de Crecimiento de Fibroblastos/biosíntesis , Factor 6 de Crecimiento de Fibroblastos/genética , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Regulación del Desarrollo de la Expresión Génica , Ratones , Ratones Transgénicos , Cresta Neural/citología , Técnicas de Cultivo de Órganos , Receptor Tipo I de Factor de Crecimiento Transformador beta , Transducción de Señal/genética , Proteína Smad1/metabolismo , Proteína Smad5/metabolismo , Proteína Smad8/metabolismo , Lengua/embriología , Enfermedades de la Lengua/genética , Factor de Crecimiento Transformador beta/genética , Proteína Wnt1/genéticaRESUMEN
OBJECTIVE: To investigate the changes of fibroblast growth factor (FGF)-6 expression in the regeneration and repair process after exercise-induced muscle damage (EIMD) and the relationship with skeletal muscle regeneration and repair. METHODS: The expression of FGF-6 at different time points was examined by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry staining after a downhill treadmill exercise. Skeletal muscle injury and regeneration at different times after EIMD was assessed by haematoxylin and eosin (H & E) staining. RESULTS: The FGF-6 protein expression was initially elevated, followed by a gradual reduction, while the changes of FGF-6 mRNA were almost all raised after the treadmill exercise. CONCLUSION: The results point out that FGF-6 is closely related to skeletal muscle regeneration and repair, probably implying a dual function in muscle regeneration.
OBJETIVO: Investigar los cambios de expresión del factor de crecimiento fibroblástico (FGF)-6 en el proceso de regeneración y reparación después de daño muscular inducido por el ejercicio (DMIE) y la relación con la reparación y regeneración del músculo esquelético. MÉTODOS: La expresión de FGF-6 en diferentes tiempos fue examinada mediante reacción en cadena de la polimerasa con transcriptasa inversa (RT-PCR) y tinción inmunohistoquímica, después de un ejercicio de carrera descendente en cinta rodante. La lesión del músculo esquelético y la regeneración en diferentes momentos después del DMIE, fueron evaluadas mediante hematoxilina y eosina (H & E). RESULTADOS: La expresión de la proteína FGF-6 fue elevada al principio, seguida por una reducción gradual, mientras que los cambios de FGF-6 mRNA fueron casi todos incrementados tras los ejercicios en la cinta rodante. CONCLUSIÓN: Nuestros resultados señalan que FGF-6 se relaciona estrechamente con la regeneración del músculo esquelético, lo que probablemente implica una función dual en la regeneración muscular.
Asunto(s)
Animales , Masculino , Ratas , Condicionamiento Físico Animal/efectos adversos , Regeneración/fisiología , Músculo Esquelético/lesiones , Factor 6 de Crecimiento de Fibroblastos/metabolismo , ARN Mensajero/metabolismo , Ratas Sprague-Dawley , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Modelos Animales de EnfermedadRESUMEN
FGFs with similar sequences can play different roles depending on the model organisms examined. Determining these roles requires knowledge of spatio-temporal Fgf gene expression patterns. In this study, we report the cloning of chick Fgf5, 6 and 7, and examine their gene expression patterns by whole mount in situ hybridization. We show that Fgf5's spatio-temporally restricted expression pattern indicates a potentially novel role during inner ear development. Fgf6 and Fgf7, although belonging to different subfamilies with diverged sequences, are expressed in similar patterns within the mesoderm. Alignment of protein sequences and phylogenetic analysis demonstrate that FGF5 and FGF6 are highly conserved between chick, human, mouse and zebrafish. FGF7 is similarly conserved except for the zebrafish, which has considerably diverged.
Asunto(s)
Pollos/metabolismo , Factor 5 de Crecimiento de Fibroblastos/genética , Factor 6 de Crecimiento de Fibroblastos/genética , Factor 7 de Crecimiento de Fibroblastos/genética , Regulación del Desarrollo de la Expresión Génica , Secuencia de Aminoácidos , Animales , Embrión de Pollo , Pollos/genética , Clonación Molecular , Secuencia Conservada , Oído Interno/embriología , Oído Interno/metabolismo , Factor 5 de Crecimiento de Fibroblastos/metabolismo , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Factor 7 de Crecimiento de Fibroblastos/metabolismo , Hibridación in Situ , Funciones de Verosimilitud , Datos de Secuencia Molecular , Especificidad de Órganos , FilogeniaRESUMEN
The tongue is a muscular organ and plays a crucial role in speech, deglutition and taste. Despite the important physiological functions of the tongue, little is known about the regulatory mechanisms of tongue muscle development. TGFß family members play important roles in regulating myogenesis, but the functional significance of Smad-dependent TGFß signaling in regulating tongue skeletal muscle development remains unclear. In this study, we have investigated Smad4-mediated TGFß signaling in the development of occipital somite-derived myogenic progenitors during tongue morphogenesis through tissue-specific inactivation of Smad4 (using Myf5-Cre;Smad4(flox/flox) mice). During the initiation of tongue development, cranial neural crest (CNC) cells occupy the tongue buds before myogenic progenitors migrate into the tongue primordium, suggesting that CNC cells play an instructive role in guiding tongue muscle development. Moreover, ablation of Smad4 results in defects in myogenic terminal differentiation and myoblast fusion. Despite compromised muscle differentiation, tendon formation appears unaffected in the tongue of Myf5-Cre;Smad4(flox/flox) mice, suggesting that the differentiation and maintenance of CNC-derived tendon cells are independent of Smad4-mediated signaling in myogenic cells in the tongue. Furthermore, loss of Smad4 results in a significant reduction in expression of several members of the FGF family, including Fgf6 and Fgfr4. Exogenous Fgf6 partially rescues the tongue myoblast fusion defect of Myf5-Cre;Smad4(flox/flox) mice. Taken together, our study demonstrates that a TGFß-Smad4-Fgf6 signaling cascade plays a crucial role in myogenic cell fate determination and lineage progression during tongue myogenesis.
Asunto(s)
Diferenciación Celular/fisiología , Regulación del Desarrollo de la Expresión Génica/fisiología , Desarrollo de Músculos/fisiología , Transducción de Señal/fisiología , Proteína Smad4/metabolismo , Lengua/embriología , Factor de Crecimiento Transformador beta/metabolismo , Animales , Western Blotting , Células Cultivadas , Factor 6 de Crecimiento de Fibroblastos/metabolismo , Citometría de Flujo , Regulación del Desarrollo de la Expresión Génica/genética , Hibridación in Situ , Ratones , Ratones Mutantes , Microscopía Electrónica de Rastreo , Mioblastos/citología , Cresta Neural/embriología , Reacción en Cadena en Tiempo Real de la Polimerasa , Transducción de Señal/genética , Proteína Smad4/genética , Tendones/citología , Lengua/citología , beta-GalactosidasaRESUMEN
Fibroblast growth factor-6 (FGF-6) is known to be the key ligand for fibroblast growth factor receptor 4 (FGFR4) during muscle regeneration but its role in bone has yet to be verified. FGFR signaling is known to be important in the initiation and regulation of osteogenesis, so in this study the actions of FGF-6 on human osteoblasts and osteoclasts were investigated. Human primary osteoblasts (hOB) were used to study the effect of FGF-6 on proliferation (by ATP quantification), signal transduction (by ERK and AKT phosphorylation), differentiation (by alkaline phosphatase activity, APA), and mineralization (by calcein staining). To study FGF-6 activity on osteoclast differentiation, human bone marrow cells were used and tartrate-resistant acid phosphatase (TRAP) multinucleated cells together with actin filaments arrangements were quantified. Human primary mature osteoclasts were used to evaluate the effect of FGF-6 on osteoclast reabsorbing activity by reabsorbed pit measurements. FGF-6 >10(-9) M as FGF-2 10(-7) M induced hOB proliferation mediated by pERK together with a reduction in APA and reduced mineralization of the treated cells. Moreover FGF-6 increased the formation of TRAP-positive multinucleated cells in a dose-dependent manner (maximal effect at 10(-8) M). FGF-6-treated cells showed also a greater percentage of cells that formed typical osteoclast sealing zones. Mature osteoclasts cultured on dentine slice increased the area of reabsorption with a maximal effect of FGF-6 at 10(-12) M. FGF-6 may be considered a regulator of bone metabolism as shown by its activity on both osteoblasts and osteoclasts.
Asunto(s)
Factor 6 de Crecimiento de Fibroblastos/metabolismo , Osteoblastos/fisiología , Osteoclastos/fisiología , Fosfatasa Ácida/metabolismo , Células de la Médula Ósea/metabolismo , Huesos/citología , Huesos/metabolismo , Diferenciación Celular , Células Cultivadas , Factor 6 de Crecimiento de Fibroblastos/genética , Regulación de la Expresión Génica , Humanos , Isoenzimas/metabolismo , Osteoblastos/citología , Osteoclastos/citología , Receptor Tipo 4 de Factor de Crecimiento de Fibroblastos/metabolismo , Transducción de Señal , Fosfatasa Ácida Tartratorresistente , Factores de TiempoRESUMEN
Sprouty (Spry) proteins were identified as negative regulators of fibroblast growth factor (FGF) signaling in vertebrates and invertebrates. Given the importance of the FGFs in myogenesis, we performed cardiotoxin injury-induced regeneration experiments on soleus muscles of both, adult control and FGF6 ( - / - ) mutant mice and analyzed the accumulation of Spry (1, 2 and 4) transcripts using semi-quantitative and real-time RT-PCR assays and in situ hybridization. We also analyzed the effects of muscle denervation on the accumulation of Spry transcripts. The three Spry genes begin to be expressed as early as the first stages of muscle regeneration and are characterized by distinct expression patterns. Moreover, Spry gene expression was highly and differentially up-regulated, precociously by the lack of FGF6, and belatedly by muscle denervation strongly suggesting that the transient rise of Spry mRNA accumulation was associated to muscle differentiation. Rescue experiments supported the idea of a specific relationship between FGF6 and Spry 2, both being known for their particular involvement in myogenesis.
Asunto(s)
Factor 6 de Crecimiento de Fibroblastos/metabolismo , Proteínas de la Membrana/biosíntesis , Músculo Esquelético/fisiología , Proteínas Proto-Oncogénicas/metabolismo , Regeneración , Proteínas Adaptadoras Transductoras de Señales , Animales , Factor 6 de Crecimiento de Fibroblastos/genética , Regulación de la Expresión Génica , Péptidos y Proteínas de Señalización Intracelular , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Desnervación Muscular , Músculo Esquelético/inervación , Isoformas de Proteínas/biosíntesis , Proteínas Serina-Treonina Quinasas , Proteínas Proto-Oncogénicas/genética , ARN Mensajero/metabolismoRESUMEN
With the use of Hoechst staining techniques, we have previously shown that the C2C12 myogenic cell line contains a side population (SP) that is largely increased in the presence of fibroblast growth factor 6 (FGF6). Here, we compared transcriptional profiles from SP and main population (MP) cells from either C2C12 or FGF6-expressing C2C12. Expression profiles of SPs show that these cells are less differentiated than MPs and display some similarities to stem cells. Moreover, principal component analysis made it possible to distinguish specific contributions of either FGF6 or differentiation effects on gene expression profiles. This demonstrated that FGF6-expanded SPs were similar to parental C2C12-derived SPs. Conversely, FGF6-treated MPs differed from parental MPs and were more related to SP cells. These results show that FGF6 pushed committed myogenic cells toward a more immature phenotype resulting in the accumulation of cells with a SP phenotype. We propose that FGF6 conditioning could provide a way to expand the pool of immature cells by myoblast dedifferentiation.