Publications by authors named "David M Ornitz"

157 Publications

Digenic Variants in the FGF21 Signaling Pathway Associated with Severe Insulin Resistance and Pseudoacromegaly.

J Endocr Soc 2020 Dec 22;4(12):bvaa138. Epub 2020 Sep 22.

Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, US.

Insulin-mediated pseudoacromegaly (IMPA) is a rare disease of unknown etiology. Here we report a 12-year-old female with acanthosis nigricans, hirsutism, and acromegalic features characteristic of IMPA. The subject was noted to have normal growth hormone secretion, with extremely elevated insulin levels. Studies were undertaken to determine a potential genetic etiology for IMPA. The proband and her family members underwent whole exome sequencing. Functional studies were undertaken to validate the pathogenicity of candidate variant alleles. Whole exome sequencing identified monoallelic, predicted deleterious variants in genes that mediate fibroblast growth factor 21 (FGF21) signaling, and which were inherited in trans from each parent. FGF21 has multiple metabolic functions but no known role in human insulin resistance syndromes. Analysis of the function of the and variants in vitro showed greatly attenuated ERK phosphorylation in response to FGF21, but not FGF2, suggesting that these variants act synergistically to inhibit endocrine FGF21 signaling but not canonical FGF2 signaling. Therefore, digenic variants in and provide a potential explanation for the subject's severe insulin resistance and may represent a novel category of insulin resistance syndromes related to FGF21.
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http://dx.doi.org/10.1210/jendso/bvaa138DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7653638PMC
December 2020

The Fgf8 subfamily (Fgf8, Fgf17 and Fgf18) is required for closure of the embryonic ventral body wall.

Development 2020 10 19;147(21). Epub 2020 Oct 19.

Cancer and Developmental Biology Lab, National Cancer Institute, National Institutes of Health, Frederick, MD 21702, USA

The closure of the embryonic ventral body wall in amniotes is an important morphogenetic event and is essential for life. Defects in human ventral wall closure are a major class of birth defect and a significant health burden. Despite this, very little is understood about how the ventral body wall is formed. Here, we show that fibroblast growth factor (FGF) ligands FGF8, FGF17 and FGF18 are essential for this process. Conditional mouse mutants for these genes display subtle migratory defects in the abdominal muscles of the ventral body wall and an enlarged umbilical ring, through which the internal organs are extruded. By refining where and when these genes are required using different Cre lines, we show that and are required in the presomitic mesoderm, whereas is required in the somites. This study identifies complex and multifactorial origins of ventral wall defects and has important implications for understanding their origins during embryonic development.
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http://dx.doi.org/10.1242/dev.189506DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595690PMC
October 2020

FGF20-FGFR1 signaling through MAPK and PI3K controls sensory progenitor differentiation in the organ of Corti.

Dev Dyn 2021 Feb 9;250(2):134-144. Epub 2020 Sep 9.

Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, USA.

Background: Fibroblast Growth Factor 20 (FGF20)-FGF receptor 1 (FGFR1) signaling is essential for cochlear hair cell (HC) and supporting cell (SC) differentiation. In other organ systems, FGFR1 signals through several intracellular pathways including MAPK (ERK), PI3K, phospholipase C ɣ (PLCɣ), and p38. Previous studies implicated MAPK and PI3K pathways in HC and SC development. We hypothesized that one or both would be important downstream mediators of FGF20-FGFR1 signaling for HC differentiation.

Results: By inhibiting pathways downstream of FGFR1 in cochlea explant cultures, we established that both MAPK and PI3K pathways are required for HC differentiation while PLCɣ and p38 pathways are not. Examining the canonical PI3K pathway, we found that while AKT is necessary for HC differentiation, it is not sufficient to rescue the Fgf20 phenotype. To determine whether PI3K functions downstream of FGF20, we inhibited Phosphatase and Tensin Homolog (PTEN) in Fgf20 explants. Overactivation of PI3K resulted in a partial rescue of the Fgf20 phenotype, demonstrating a requirement for PI3K downstream of FGF20. Consistent with a requirement for the MAPK pathway for FGF20-regulated HC differentiation, we show that treating Fgf20 explants with FGF9 increased levels of dpERK.

Conclusions: Together, these data provide evidence that both MAPK and PI3K are important downstream mediators of FGF20-FGFR1 signaling during HC and SC differentiation.
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http://dx.doi.org/10.1002/dvdy.231DOI Listing
February 2021

FAM20B-catalyzed glycosaminoglycans control murine tooth number by restricting FGFR2b signaling.

BMC Biol 2020 07 14;18(1):87. Epub 2020 Jul 14.

Department of Biomedical Sciences, Texas A&M University College of Dentistry, 3302 Gaston Ave, Dallas, TX, 75246, USA.

Background: The formation of supernumerary teeth is an excellent model for studying the molecular mechanisms that control stem/progenitor cell homeostasis needed to generate a renewable source of replacement cells and tissues. Although multiple growth factors and transcriptional factors have been associated with supernumerary tooth formation, the regulatory inputs of extracellular matrix in this regenerative process remains poorly understood.

Results: In this study, we present evidence that disrupting glycosaminoglycans (GAGs) in the dental epithelium of mice by inactivating FAM20B, a xylose kinase essential for GAG assembly, leads to supernumerary tooth formation in a pattern reminiscent of replacement teeth. The dental epithelial GAGs confine murine tooth number by restricting the homeostasis of Sox2(+) dental epithelial stem/progenitor cells in a non-autonomous manner. FAM20B-catalyzed GAGs regulate the cell fate of dental lamina by restricting FGFR2b signaling at the initial stage of tooth development to maintain a subtle balance between the renewal and differentiation of Sox2(+) cells. At the later cap stage, WNT signaling functions as a relay cue to facilitate the supernumerary tooth formation.

Conclusions: The novel mechanism we have characterized through which GAGs control the tooth number in mice may also be more broadly relevant for potentiating signaling interactions in other tissues during development and tissue homeostasis.
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http://dx.doi.org/10.1186/s12915-020-00813-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7359594PMC
July 2020

Analysis of FGF20-regulated genes in organ of Corti progenitors by translating ribosome affinity purification.

Dev Dyn 2020 10 10;249(10):1217-1242. Epub 2020 Jul 10.

Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, USA.

Background: Understanding the mechanisms that regulate hair cell (HC) differentiation in the organ of Corti (OC) is essential to designing genetic therapies for hearing loss due to HC loss or damage. We have previously identified Fibroblast Growth Factor 20 (FGF20) as having a key role in HC and supporting cell differentiation in the mouse OC. To investigate the genetic landscape regulated by FGF20 signaling in OC progenitors, we employ Translating Ribosome Affinity Purification combined with Next Generation RNA Sequencing (TRAPseq) in the Fgf20 lineage.

Results: We show that TRAPseq targeting OC progenitors effectively enriched for RNA from this rare cell population. TRAPseq identified differentially expressed genes (DEGs) downstream of FGF20, including Etv4, Etv5, Etv1, Dusp6, Hey1, Hey2, Heyl, Tectb, Fat3, Cpxm2, Sall1, Sall3, and cell cycle regulators such as Cdc20. Analysis of Cdc20 conditional-null mice identified decreased cochlea length, while analysis of Sall1-null and Sall1-ΔZn2-10 mice, which harbor a mutation that causes Townes-Brocks syndrome, identified a decrease in outer hair cell number.

Conclusions: We present two datasets: genes with enriched expression in OC progenitors, and DEGs downstream of FGF20 in the embryonic day 14.5 cochlea. We validate select DEGs via in situ hybridization and in vivo functional studies in mice.
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http://dx.doi.org/10.1002/dvdy.211DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7575056PMC
October 2020

Geminin is required for Hox gene regulation to pattern the developing limb.

Dev Biol 2020 08 23;464(1):11-23. Epub 2020 May 23.

Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA. Electronic address:

Development of the complex structure of the vertebrate limb requires carefully orchestrated interactions between multiple regulatory pathways and proteins. Among these, precise regulation of 5' Hox transcription factor expression is essential for proper limb bud patterning and elaboration of distinct limb skeletal elements. Here, we identified Geminin (Gmnn) as a novel regulator of this process. A conditional model of Gmnn deficiency resulted in loss or severe reduction of forelimb skeletal elements, while both the forelimb autopod and hindlimb were unaffected. 5' Hox gene expression expanded into more proximal and anterior regions of the embryonic forelimb buds in this Gmnn-deficient model. A second conditional model of Gmnn deficiency instead caused a similar but less severe reduction of hindlimb skeletal elements and hindlimb polydactyly, while not affecting the forelimb. An ectopic posterior SHH signaling center was evident in the anterior hindlimb bud of Gmnn-deficient embryos in this model. This center ectopically expressed Hoxd13, the HOXD13 target Shh, and the SHH target Ptch1, while these mutant hindlimb buds also had reduced levels of the cleaved, repressor form of GLI3, a SHH pathway antagonist. Together, this work delineates a new role for Gmnn in modulating Hox expression to pattern the vertebrate limb.
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http://dx.doi.org/10.1016/j.ydbio.2020.05.007DOI Listing
August 2020

FGF9 and FGF10 activate distinct signaling pathways to direct lung epithelial specification and branching.

Sci Signal 2020 03 3;13(621). Epub 2020 Mar 3.

Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO 63110, USA.

Fibroblast growth factors (FGFs) 9 and 10 are essential during the pseudoglandular stage of lung development. Mesothelium-produced FGF9 is principally responsible for mesenchymal growth, whereas epithelium-produced FGF9 and mesenchyme-produced FGF10 guide lung epithelial development, and loss of either of these ligands affects epithelial branching. Because FGF9 and FGF10 activate distinct FGF receptors (FGFRs), we hypothesized that they would control distinct developmental processes. Here, we found that FGF9 signaled through epithelial FGFR3 to directly promote distal epithelial fate specification and inhibit epithelial differentiation. By contrast, FGF10 signaled through epithelial FGFR2b to promote epithelial proliferation and differentiation. Furthermore, FGF9-FGFR3 signaling functionally opposed FGF10-FGFR2b signaling, and FGFR3 preferentially used downstream phosphoinositide 3-kinase (PI3K) pathways, whereas FGFR2b relied on downstream mitogen-activated protein kinase (MAPK) pathways. These data demonstrate that, within lung epithelial cells, different FGFRs function independently; they bind receptor-specific ligands and direct distinct developmental functions through the activation of distinct downstream signaling pathways.
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http://dx.doi.org/10.1126/scisignal.aay4353DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7271816PMC
March 2020

Identification of a FGF18-expressing alveolar myofibroblast that is developmentally cleared during alveologenesis.

Development 2020 01 17;147(2). Epub 2020 Jan 17.

Department of Developmental Biology, Washington University School of Medicine, St Louis, MO 63110, USA

Alveologenesis is an essential developmental process that increases the surface area of the lung through the formation of septal ridges. In the mouse, septation occurs postnatally and is thought to require the alveolar myofibroblast (AMF). Though abundant during alveologenesis, markers for AMFs are minimally detected in the adult. After septation, the alveolar walls thin to allow efficient gas exchange. Both loss of AMFs or retention and differentiation into another cell type during septal thinning have been proposed. Using a novel allele to lineage trace AMFs, we demonstrate that most AMFs are developmentally cleared during alveologenesis. Lung mesenchyme also contains other poorly described cell types, including alveolar lipofibroblasts (ALF). We show that marks both AMFs as well as ALFs, and lineage tracing shows that ALFs are retained in adult alveoli while AMFs are lost. We further show that multiple immune cell populations contain lineage-labeled particles, suggesting a phagocytic role in the clearance of AMFs. The demonstration that the AMF lineage is depleted during septal thinning through a phagocytic process provides a mechanism for the clearance of a transient developmental cell population.
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http://dx.doi.org/10.1242/dev.181032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6983722PMC
January 2020

FGFR2 Is Required for AEC2 Homeostasis and Survival after Bleomycin-induced Lung Injury.

Am J Respir Cell Mol Biol 2020 05;62(5):608-621

Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois; and.

Alveolar epithelial cell (AEC) injury is central to the pathogenesis of pulmonary fibrosis. Epithelial FGF (fibroblast growth factor) signaling is essential for recovery from hyperoxia- and influenza-induced lung injury, and treatment with FGFs is protective in experimental lung injury. The cell types involved in the protective effect of FGFs are not known. We hypothesized that FGF signaling in type II AECs (AEC2s) is critical in bleomycin-induced lung injury and fibrosis. To test this hypothesis, we generated mice with tamoxifen-inducible deletion of FGFR1-3 (fibroblast growth factor receptors 1, 2, and 3) in surfactant protein C-positive (SPC) AEC2s (SPC triple conditional knockout [SPC-TCKO]). In the absence of injury, SPC-TCKO mice had fewer AEC2s, decreased (surfactant protein C gene) expression, increased alveolar diameter, and increased collagen deposition. After intratracheal bleomycin administration, SPC-TCKO mice had increased mortality, lung edema, and BAL total protein, and flow cytometry and immunofluorescence revealed a loss of AEC2s. To reduce mortality of SPC-TCKO mice to less than 50%, a 25-fold dose reduction of bleomycin was required. Surviving bleomycin-injured SPC-TCKO mice had increased collagen deposition, fibrosis, and ACTA2 expression and decreased epithelial gene expression. Inducible inactivation of individual or revealed that , but not , was responsible for the increased mortality and lung injury after bleomycin administration. In conclusion, AEC2-specific FGFR2 is critical for survival in response to bleomycin-induced lung injury. These data also suggest that a population of SPC AEC2s require FGFR2 signaling for maintenance in the adult lung. Preventing epithelial FGFR inhibition and/or activating FGFRs in alveolar epithelium may therefore represent a novel approach to treating lung injury and reducing fibrosis.
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http://dx.doi.org/10.1165/rcmb.2019-0079OCDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193788PMC
May 2020

Mouse genetics identifies unique and overlapping functions of fibroblast growth factor receptors in keratinocytes.

J Cell Mol Med 2020 01 12;24(2):1774-1785. Epub 2019 Dec 12.

Department of Biology, Institute of Molecular Health Sciences, ETH Zurich, Zurich, Switzerland.

Fibroblast growth factors (FGFs) are key regulators of tissue development, homeostasis and repair, and abnormal FGF signalling is associated with various human diseases. In human and murine epidermis, FGF receptor 3 (FGFR3) activation causes benign skin tumours, but the consequences of FGFR3 deficiency in this tissue have not been determined. Here, we show that FGFR3 in keratinocytes is dispensable for mouse skin development, homeostasis and wound repair. However, the defect in the epidermal barrier and the resulting inflammatory skin disease that develops in mice lacking FGFR1 and FGFR2 in keratinocytes were further aggravated upon additional loss of FGFR3. This caused fibroblast activation and fibrosis in the FGFR1/FGFR2 double-knockout mice and even more in mice lacking all three FGFRs, revealing functional redundancy of FGFR3 with FGFR1 and FGFR2 for maintaining the epidermal barrier. Taken together, our study demonstrates that FGFR1, FGFR2 and FGFR3 act together to maintain epidermal integrity and cutaneous homeostasis, with FGFR2 being the dominant receptor.
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http://dx.doi.org/10.1111/jcmm.14871DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6991627PMC
January 2020

β-Catenin is required for radial cell patterning and identity in the developing mouse cochlea.

Proc Natl Acad Sci U S A 2019 10 30;116(42):21054-21060. Epub 2019 Sep 30.

Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305;

Development of multicellular organs requires the coordination of cell differentiation and patterning. Critical for sound detection, the mammalian organ of Corti contains functional units arranged tonotopically along the cochlear turns. Each unit consists of sensory hair cells intercalated by nonsensory supporting cells, both specified and radially patterned with exquisite precision during embryonic development. However, how cell identity and radial patterning are jointly controlled is poorly understood. Here we show that β-catenin is required for specification of hair cell and supporting cell subtypes and radial patterning of the cochlea in vivo. In 2 mouse models of conditional β-catenin deletion, early specification of Myosin7-expressing hair cells and Prox1-positive supporting cells was preserved. While β-catenin-deficient cochleae expressed FGF8 and FGFR3, both of which are essential for pillar cell specification, the radial patterning of organ of Corti was disrupted, revealed by aberrant expression of cadherins and the pillar cell markers P75 and Lgr6. Moreover, β-catenin ablation caused duplication of FGF8-positive inner hair cells and reduction of outer hair cells without affecting the overall hair cell density. In contrast, in another transgenic model with suppressed transcriptional activity of β-catenin but preserved cell adhesion function, both specification and radial patterning of the organ of Corti were intact. Our study reveals specific functions of β-catenin in governing cell identity and patterning mediated through cell adhesion in the developing cochlea.
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http://dx.doi.org/10.1073/pnas.1910223116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6800344PMC
October 2019

Crouzon syndrome mouse model exhibits cartilage hyperproliferation and defective segmentation in the developing trachea.

Sci China Life Sci 2019 Oct 26;62(10):1375-1380. Epub 2019 Aug 26.

Laboratory of Genetics, University of Wisconsin, Madison, WI, 53706, USA.

Crouzon syndrome is the result of a gain-of-function point mutation in FGFR2. Mimicking the human mutation, a mouse model of Crouzon syndrome (Fgfr) recapitulates patient deformities, including failed tracheal cartilage segmentation, resulting in a cartilaginous sleeve in the homozygous mutants. We found that the Fgfr2 mutants exhibited an increase in chondrocytes prior to segmentation. This increase is due at least in part to over proliferation. Genetic ablation of chondrocytes in the mutant led to restoration of segmentation in the lateral but not central portion of the trachea. These results suggest that in the Fgfr2 mutants, increased cartilage cell proliferation precedes and contributes to the disruption of cartilage segmentation in the developing trachea.
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http://dx.doi.org/10.1007/s11427-019-9568-xDOI Listing
October 2019

FGF2-induced STAT3 activation regulates pathologic neovascularization.

Exp Eye Res 2019 10 23;187:107775. Epub 2019 Aug 23.

Department of Ophthalmology and Visual Sciences, 660 S. Euclid Ave, St. Louis, MO, 63110, USA; Department of Developmental Biology, 660 S. Euclid Ave, St. Louis, MO, 63110, USA; Department of Medicine, Washington University in St. Louis School of Medicine, 660 S. Euclid Ave, St. Louis, MO, 63110, USA. Electronic address:

Cell-autonomous endothelial cell (EC) fibroblast growth factor receptor (FGFR) signaling through FGFR1/2 is essential for injury-induced wound vascularization and pathologic neovascularization as in blinding eye diseases such as age-related macular degeneration. Which FGF ligand(s) is critical in regulating angiogenesis is unknown. Utilizing ex vivo models of choroidal endothelial sprouting and in vivo models of choroidal neovascularization (CNV), we demonstrate here that only FGF2 is the essential ligand. Though FGF-FGFR signaling can activate multiple intracellular signaling pathways, we show that FGF2 regulates pathogenic angiogenesis via STAT3 activation. The identification of FGF2 as a critical mediator in aberrant neovascularization provides a new opportunity for developing multi-target therapies in blinding eye diseases especially given the limitations of anti-VEGF monotherapy.
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http://dx.doi.org/10.1016/j.exer.2019.107775DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6759401PMC
October 2019

Generation and validation of novel conditional flox and inducible Cre alleles targeting fibroblast growth factor 18 (Fgf18).

Dev Dyn 2019 09 22;248(9):882-893. Epub 2019 Jul 22.

Department of Developmental Biology, Washington University School of Medicine, Saint Louis, Missouri.

Background: Fibroblast growth factor 18 (FGF18) functions in the development of several tissues, including the lung, limb bud, palate, skeleton, central nervous system, and hair follicle. Mice containing a germline knockout of Fgf18 (Fgf18 ) die shortly after birth. Postnatally, FGF18 is being evaluated for pathogenic roles in fibrosis and several types of cancer. The specific cell types that express FGF18 have been difficult to identify, and the function of FGF18 in postnatal development and tissue homeostasis has been hampered by the perinatal lethality of Fgf18 null mice.

Results: We engineered a floxed allele of Fgf18 (Fgf18 ) that allows conditional gene inactivation and a CreER knockin allele (Fgf18 ) that allows the precise identification of cells that express Fgf18 and their lineage. We validated the Fgf18 allele by targeting it in mesenchymal tissue and primary mesoderm during embryonic development, resulting in similar phenotypes to those observed in Fgf18 null mice. We also use the Fgf18 allele, in combination with a conditional fluorescent reporter to confirm known and identify new sites of Fgf18 expression.

Conclusion: These alleles will be useful to investigate FGF18 function during organogenesis and tissue homeostasis, and to target specific cell lineages at embryonic and postnatal time points.
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http://dx.doi.org/10.1002/dvdy.85DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7029619PMC
September 2019

Sox2 and FGF20 interact to regulate organ of Corti hair cell and supporting cell development in a spatially-graded manner.

PLoS Genet 2019 07 5;15(7):e1008254. Epub 2019 Jul 5.

Department of Developmental Biology; Washington University School of Medicine; St. Louis, Missouri, United States of America.

The mouse organ of Corti, housed inside the cochlea, contains hair cells and supporting cells that transduce sound into electrical signals. These cells develop in two main steps: progenitor specification followed by differentiation. Fibroblast Growth Factor (FGF) signaling is important in this developmental pathway, as deletion of FGF receptor 1 (Fgfr1) or its ligand, Fgf20, leads to the loss of hair cells and supporting cells from the organ of Corti. However, whether FGF20-FGFR1 signaling is required during specification or differentiation, and how it interacts with the transcription factor Sox2, also important for hair cell and supporting cell development, has been a topic of debate. Here, we show that while FGF20-FGFR1 signaling functions during progenitor differentiation, FGFR1 has an FGF20-independent, Sox2-dependent role in specification. We also show that a combination of reduction in Sox2 expression and Fgf20 deletion recapitulates the Fgfr1-deletion phenotype. Furthermore, we uncovered a strong genetic interaction between Sox2 and Fgf20, especially in regulating the development of hair cells and supporting cells towards the basal end and the outer compartment of the cochlea. To explain this genetic interaction and its effects on the basal end of the cochlea, we provide evidence that decreased Sox2 expression delays specification, which begins at the apex of the cochlea and progresses towards the base, while Fgf20-deletion results in premature onset of differentiation, which begins near the base of the cochlea and progresses towards the apex. Thereby, Sox2 and Fgf20 interact to ensure that specification occurs before differentiation towards the cochlear base. These findings reveal an intricate developmental program regulating organ of Corti development along the basal-apical axis of the cochlea.
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http://dx.doi.org/10.1371/journal.pgen.1008254DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6636783PMC
July 2019

Osteocyte Death and Bone Overgrowth in Mice Lacking Fibroblast Growth Factor Receptors 1 and 2 in Mature Osteoblasts and Osteocytes.

J Bone Miner Res 2019 09 17;34(9):1660-1675. Epub 2019 Jun 17.

Musculoskeletal Research Center, Washington University School of Medicine, St. Louis, MO, USA.

Fibroblast growth factor (FGF) signaling pathways have well-established roles in skeletal development, with essential functions in both chondrogenesis and osteogenesis. In mice, previous conditional knockout studies suggested distinct roles for FGF receptor 1 (FGFR1) signaling at different stages of osteogenesis and a role for FGFR2 in osteoblast maturation. However, the potential for redundancy among FGFRs and the mechanisms and consequences of stage-specific osteoblast lineage regulation were not addressed. Here, we conditionally inactivate Fgfr1 and Fgfr2 in mature osteoblasts with an Osteocalcin (OC)-Cre or Dentin matrix protein 1 (Dmp1)-CreER driver. We find that young mice lacking both receptors or only FGFR1 are phenotypically normal. However, between 6 and 12 weeks of age, OC-Cre Fgfr1/Fgfr2 double- and Fgfr1 single-conditional knockout mice develop a high bone mass phenotype with increased periosteal apposition, increased and disorganized endocortical bone with increased porosity, and biomechanical properties that reflect increased bone mass but impaired material properties. Histopathological and gene expression analyses show that this phenotype is preceded by a striking loss of osteocytes and accompanied by activation of the Wnt/β-catenin signaling pathway. These data identify a role for FGFR1 signaling in mature osteoblasts/osteocytes that is directly or indirectly required for osteocyte survival and regulation of bone mass during postnatal bone growth. © 2019 American Society for Bone and Mineral Research.
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http://dx.doi.org/10.1002/jbmr.3742DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6744314PMC
September 2019

Characterisation of endogenous players in fibroblast growth factor-regulated functions of hypothalamic tanycytes and energy-balance nuclei.

J Neuroendocrinol 2019 08 8;31(8):e12750. Epub 2019 Jul 8.

School of Biological Sciences, University of East Anglia, Norwich, UK.

The mammalian hypothalamus regulates key homeostatic and neuroendocrine functions ranging from circadian rhythm and energy balance to growth and reproductive cycles via the hypothalamic-pituitary and hypothalamic-thyroid axes. In addition to its neurones, tanycytes are taking centre stage in the short- and long-term augmentation and integration of diverse hypothalamic functions, although the genetic regulators and mediators of their involvement are poorly understood. Exogenous interventions have implicated fibroblast growth factor (FGF) signalling, although the focal point of the action of FGF and any role for putative endogenous players also remains elusive. We carried out a comprehensive high-resolution screen of FGF signalling pathway mediators and modifiers using a combination of in situ hybridisation, immunolabelling and transgenic reporter mice, aiming to map their spatial distribution in the adult hypothalamus. Our findings suggest that β-tanycytes are the likely focal point of exogenous and endogenous action of FGF in the third ventricular wall, utilising FGF receptor (FGFR)1 and FGFR2 IIIc isoforms, but not FGFR3. Key IIIc-activating endogenous ligands include FGF1, 2, 9 and 18, which are expressed by a subset of ependymal and parenchymal cells. In the parenchymal compartment, FGFR1-3 show divergent patterns, with FGFR1 being predominant in neuronal nuclei and expression of FGFR3 being associated with glial cell function. Intracrine FGFs are also present, suggestive of multiple modes of FGF function. Our findings provide a testable framework for understanding the complex role of FGFs with respect to regulating the metabolic endocrine and neurogenic functions of hypothalamus in vivo.
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http://dx.doi.org/10.1111/jne.12750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6772024PMC
August 2019

Effect of FGF/FGFR pathway blocking on lung adenocarcinoma and its cancer-associated fibroblasts.

J Pathol 2019 10 24;249(2):193-205. Epub 2019 Jun 24.

Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Tokyo, Japan.

Cancer-associated fibroblasts (CAFs) are known to promote tumourigenesis through various mechanisms. Fibroblast growth factor (FGF)/FGF receptor (FGFR)-dependent lung cancers have been described. We have developed a mouse model of lung adenocarcinoma that was constructed through the induction of Fgf9 overexpression in type 2 alveolar cells. The expression of Fgf9 in adult lungs resulted in the rapid development of multiple adenocarcinoma-like tumour nodules. Here, we have characterised the contribution of CAFs and the Fgf/Fgfr signalling pathway in maintaining the lung tumours initiated by Fgf9 overexpression. We found that CAF-secreted Fgf2 contributes to tumour cell growth. CAFs overexpressed Tgfb, Mmp7, Fgf9, and Fgf2; synthesised more collagen, and secreted inflammatory cell-recruiting cytokines. CAFs also enhanced the conversion of tumour-associated macrophages (TAMs) to the tumour-supportive M2 phenotype but did not influence angiogenesis. In vivo inhibition of Fgfrs during early lung tumour development resulted in significantly smaller and fewer tumour nodules, whereas inhibition in established lung tumours caused a significant reduction in tumour size and number. Fgfr inhibition also influenced tumour stromal cells, as it significantly abolished TAM recruitment and reduced tumour vascularity. However, the withdrawal of the inhibitor caused a significant recurrence/regrowth of Fgf/Fgfr-independent lung tumours. These recurrent tumours did not possess a higher proliferative or propagative potential. Our results provide evidence that fibroblasts associated with the Fgf9-induced lung adenocarcinoma provide multiple means of support to the tumour. Although the Fgfr blocker significantly suppressed the tumour and its stromal cells, it was not sufficient to completely eliminate the tumour, probably due to the emergence of alternative (resistance/maintenance) mechanism(s). This model represents an excellent tool to further study the complex interactions between CAFs, their related chemokines, and the progression of lung adenocarcinoma; it also provides further evidence to support the need for a combinatorial strategy to treat lung cancer. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/path.5290DOI Listing
October 2019

Diagnosis and Pathophysiological Mechanisms of Group 3 Hypoxia-Induced Pulmonary Hypertension.

Curr Treat Options Cardiovasc Med 2019 Mar 22;21(3):16. Epub 2019 Mar 22.

Department of Pediatrics, Washington University School of Medicine, One Children's place, Campus Box 8116-NWT, St. Louis, MO, 63132, USA.

Purpose Of Review: Group 3 hypoxia-induced pulmonary hypertension (PH) is an important and increasingly diagnosed condition in both the pediatric and adult population. The majority of pulmonary hypertension studies to date and all three classes of drug therapies were designed to focus on group 1 PH. There is a clear unmet medical need for understanding the molecular mechanisms of group 3 PH and a need for novel non-invasive methods of assessing PH in neonates.

Recent Findings: Several growth factors are expressed in patients and in animal models of group 3 PH and are thought to contribute to the pathophysiology of this disease. Here, we review some of the findings on the roles of vascular endothelial growth factor A (VEGFA), platelet-derived growth factor B (PDGFB), transforming growth factor-beta (TGFB1), and fibroblast growth factors (FGF) in PH. Additionally, we discuss novel uses of echocardiographic parameters in assessing right ventricular form and function. FGF2, TGFB, PDGFB, and VEGFA may serve as biomarkers in group 3 PH along with echocardiographic methods to diagnose and follow right ventricle function. FGFs and VEGFs may also function in the pathophysiology of group 3 PH.
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http://dx.doi.org/10.1007/s11936-019-0718-3DOI Listing
March 2019

Fibroblast growth factors in skeletal development.

Curr Top Dev Biol 2019 3;133:195-234. Epub 2019 Jan 3.

UMR-1132 Inserm (Institut national de la Santé et de la Recherche Médicale) and University Paris Diderot, Sorbonne Paris Cité, Hôpital Lariboisière, Paris, France.

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are expressed throughout all stages of skeletal development. In the limb bud and in cranial mesenchyme, FGF signaling is important for formation of mesenchymal condensations that give rise to bone. Once skeletal elements are initiated and patterned, FGFs regulate both endochondral and intramembranous ossification programs. In this chapter, we review functions of the FGF signaling pathway during these critical stages of skeletogenesis, and explore skeletal malformations in humans that are caused by mutations in FGF signaling molecules.
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http://dx.doi.org/10.1016/bs.ctdb.2018.11.020DOI Listing
March 2020

Neural crest-derived neurons invade the ovary but not the testis during mouse gonad development.

Proc Natl Acad Sci U S A 2019 03 28;116(12):5570-5575. Epub 2019 Feb 28.

Department of Cell Biology, Duke University Medical Center, Durham, NC 27710;

Testes and ovaries undergo sex-specific morphogenetic changes and adopt strikingly different morphologies, despite the fact that both arise from a common precursor, the bipotential gonad. Previous studies showed that recruitment of vasculature is critical for testis patterning. However, vasculature is not recruited into the early ovary. Peripheral innervation is involved in patterning development of many organs but has been given little attention in gonad development. In this study, we show that while innervation in the male reproductive complex is restricted to the epididymis and vas deferens and never invades the interior of the testis, neural crest-derived innervation invades the interior of the ovary around E16.5. Individual neural crest cells colonize the ovary, differentiate into neurons and glia, and form a dense neural network within the ovarian medulla. Using a sex-reversing mutant mouse line, we show that innervation is specific to ovary development, is not dependent on the genetic sex of gonadal or neural crest cells, and may be blocked by repressive guidance signals elevated in the male pathway. This study reveals another aspect of sexually dimorphic gonad development, establishes a precise timeline and structure of ovarian innervation, and raises many questions for future research.
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http://dx.doi.org/10.1073/pnas.1814930116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431225PMC
March 2019

Dermal Condensate Niche Fate Specification Occurs Prior to Formation and Is Placode Progenitor Dependent.

Dev Cell 2019 01 27;48(1):32-48.e5. Epub 2018 Dec 27.

Black Family Stem Cell Institute, Icahn School of Medicine at Mount Sinai, Atran Building AB7-10C, Box 1020, New York, NY 10029, USA; Department of Cell, Developmental, and Regenerative Biology, Icahn School of Medicine at Mount Sinai, Atran Building AB7-10C, Box 1020, New York, NY 10029, USA; Graduate School of Biomedical Sciences, Icahn School of Medicine at Mount Sinai, Atran Building AB7-10C, Box 1020, New York, NY 10029, USA; Department of Dermatology, Icahn School of Medicine at Mount Sinai, Atran Building AB7-10C, Box 1020, New York, NY 10029, USA. Electronic address:

Cell fate transitions are essential for specification of stem cells and their niches, but the precise timing and sequence of molecular events during embryonic development are largely unknown. Here, we identify, with 3D and 4D microscopy, unclustered precursors of dermal condensates (DC), signaling niches for epithelial progenitors in hair placodes. With population-based and single-cell transcriptomics, we define a molecular time-lapse from pre-DC fate specification through DC niche formation and establish the developmental trajectory as the DC lineage emerges from fibroblasts. Co-expression of downregulated fibroblast and upregulated DC genes in niche precursors reveals a transitory molecular state following a proliferation shutdown. Waves of transcription factor and signaling molecule expression then coincide with DC formation. Finally, ablation of epidermal Wnt signaling and placode-derived FGF20 demonstrates their requirement for pre-DC specification. These findings uncover a progenitor-dependent niche precursor fate and the transitory molecular events controlling niche formation and function.
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http://dx.doi.org/10.1016/j.devcel.2018.11.034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6370312PMC
January 2019

Impaired tumor growth and angiogenesis in mice heterozygous for Vegfr2 (Flk1).

Sci Rep 2018 10 3;8(1):14724. Epub 2018 Oct 3.

Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA.

VEGF signaling through its tyrosine kinase receptor, VEGFR2 (FLK1), is critical for tumor angiogenesis. Previous studies have identified a critical gene dosage effect of VegfA in embryonic development and vessel homeostasis, neovascularization, and tumor growth, and potent inhibitors of VEGFR2 have been used to treat a variety of cancers. Inhibition of FGFR signaling has also been considered as an antiangiogenic approach to treat a variety of cancers. Inhibition of VEGFR2 with neutralizing antibodies or with pharmacological inhibitors of the VEGFR tyrosine kinase domain has at least short-term efficacy with some cancers; however, also affects vessel homeostasis, leading to adverse complications. We investigate gene dosage effects of Vegfr2, Fgfr1, and Fgfr2 in three independent mouse models of tumorigenesis: two-stage skin chemical carcinogenesis, and sub-cutaneous transplantation of B16F0 melanoma and Lewis Lung Carcinoma (LLC). Mice heterozygous for Vegfr2 display profound defects in supporting tumor growth and angiogenesis. Unexpectedly, additional deletion of endothelial Fgfr1 and Fgfr2 in Vegfr2 heterozygous mice shows similar tumor growth and angiogenesis as the Vegfr2 heterozygous mice. Notably, hematopoietic deletion of two alleles of Vegfr2 had minimal impact on tumor growth, with little effect on angiogenesis, reinforcing the importance of endothelial Vegfr2 heterozygosity. These studies reveal previously unrecognized Vegfr2 gene dosage effects in tumor angiogenesis and a lack of synergy between VEGFR2 and endothelial FGFR1/2 signaling during tumor growth.
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http://dx.doi.org/10.1038/s41598-018-33037-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6170482PMC
October 2018

Sculpting the skull through neurosensory epithelial-mesenchymal signaling.

Dev Dyn 2019 01 24;248(1):88-97. Epub 2018 Sep 24.

Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri.

The vertebrate skull is a complex structure housing the brain and specialized sensory organs, including the eye, the inner ear, and the olfactory system. The close association between bones of the skull and the sensory organs they encase has posed interesting developmental questions about how the tissues scale with one another. Mechanisms that regulate morphogenesis of the skull are hypothesized to originate in part from the encased neurosensory organs. Conversely, the developing skull is hypothesized to regulate the growth of neurosensory organs, through mechanical forces or molecular signaling. Here, we review studies of epithelial-mesenchymal interactions during inner ear and olfactory system development that may coordinate the growth of the two sensory organs with their surrounding bone. We highlight recent progress in the field and provide evidence that mechanical forces arising from bone growth may affect olfactory epithelium development. Developmental Dynamics 248:88-97, 2019. © 2018 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/dvdy.24664DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6312752PMC
January 2019

FGF20-Expressing, Wnt-Responsive Olfactory Epithelial Progenitors Regulate Underlying Turbinate Growth to Optimize Surface Area.

Dev Cell 2018 09 9;46(5):564-580.e5. Epub 2018 Aug 9.

Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA. Electronic address:

The olfactory epithelium (OE) is a neurosensory organ required for the sense of smell. Turbinates, bony projections from the nasal cavity wall, increase the surface area within the nasal cavity lined by the OE. Here, we use engineered fibroblast growth factor 20 (Fgf20) knockin alleles to identify a population of OE progenitor cells that expand horizontally during development to populate all lineages of the mature OE. We show that these Fgf20-positive epithelium-spanning progenitor (FEP) cells are responsive to Wnt/β-Catenin signaling. Wnt signaling suppresses FEP cell differentiation into OE basal progenitors and their progeny and positively regulates Fgf20 expression. We further show that FGF20 signals to the underlying mesenchyme to regulate the growth of turbinates. These studies thus identify a population of OE progenitor cells that function to scale OE surface area with the underlying turbinates.
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http://dx.doi.org/10.1016/j.devcel.2018.07.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7271766PMC
September 2018

Fibroblast growth factor 2 decreases bleomycin-induced pulmonary fibrosis and inhibits fibroblast collagen production and myofibroblast differentiation.

J Pathol 2018 09 5;246(1):54-66. Epub 2018 Jul 5.

University of Chicago, Department of Medicine, Section of Pulmonary and Critical Care Medicine, Chicago, IL, USA.

Fibroblast growth factor (FGF) signaling has been implicated in the pathogenesis of pulmonary fibrosis. Mice lacking FGF2 have increased mortality and impaired epithelial recovery after bleomycin exposure, supporting a protective or reparative function following lung injury. To determine whether FGF2 overexpression reduces bleomycin-induced injury, we developed an inducible genetic system to express FGF2 in type II pneumocytes. Double-transgenic (DTG) mice with doxycycline-inducible overexpression of human FGF2 (SPC-rtTA;TRE-hFGF2) or single-transgenic controls were administered intratracheal bleomycin and fed doxycycline chow, starting at either day 0 or day 7. In addition, wild-type mice received intratracheal or intravenous recombinant FGF2, starting at the time of bleomycin treatment. Compared to controls, doxycycline-induced DTG mice had decreased pulmonary fibrosis 21 days after bleomycin, as assessed by gene expression and histology. This beneficial effect was seen when FGF2 overexpression was induced at day 0 or day 7 after bleomycin. FGF2 overexpression did not alter epithelial gene expression, bronchoalveolar lavage cellularity or total protein. In vitro studies using primary mouse and human lung fibroblasts showed that FGF2 strongly inhibited baseline and TGFβ1-induced expression of alpha smooth muscle actin (αSMA), collagen, and connective tissue growth factor. While FGF2 did not suppress phosphorylation of Smad2 or Smad-dependent gene expression, FGF2 inhibited TGFβ1-induced stress fiber formation and serum response factor-dependent gene expression. FGF2 inhibition of stress fiber formation and αSMA requires FGF receptor 1 (FGFR1) and downstream MEK/ERK, but not AKT signaling. In summary, overexpression of FGF2 protects against bleomycin-induced pulmonary fibrosis in vivo and reverses TGFβ1-induced collagen and αSMA expression and stress fiber formation in lung fibroblasts in vitro, without affecting either inflammation or epithelial gene expression. Our results suggest that in the lung, FGF2 is antifibrotic in part through decreased collagen expression and fibroblast to myofibroblast differentiation. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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http://dx.doi.org/10.1002/path.5106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6175645PMC
September 2018

Tumor associated macrophages support the growth of FGF9-induced lung adenocarcinoma by multiple mechanisms.

Lung Cancer 2018 05 2;119:25-35. Epub 2018 Mar 2.

Division of Pulmonary Medicine, Department of Medicine, Keio University School of Medicine, Tokyo, Japan. Electronic address:

Objectives: Tumor-associated macrophages (TAMs) are known to promote tumorigenesis but the mechanism(s) remain elusive. We have developed a mouse model of lung cancer that is initiated through an inducible overexpression of fibroblast growth factor 9 (FGF9) in type-2 pneumocytes. Expression of FGF9 in adult lungs resulted in a rapid development of multiple adenocarcinoma-like tumor nodules, and is associated with an intense immunological reaction. The purpose of this study is to characterize the immune response to the FGF9-induced lung adenocarcinoma and to determine the contribution of TAMs to growth and survival of these tumors.

Materials And Methods: We used flow cytometry, immunostaining, RT-PCR and in vitro culture system on various cell populations isolated from the FGF9-induced adenocarcinoma mouse lungs.

Results: Immunostaining demonstrated that the majority of the inflammatory cells recruited to FGF9-induced lung tumors were macrophages. These TAMs were enriched for the alternatively activated (M2) macrophage subtype. TAMs performed a significantly high immune suppressive function on T-cells and displayed high levels of arginase-1 expression and activity. The growth and colony forming potential of tumor cells was induced by co-culture with TAMs. Additionally, TAMs were shown to promote fibroblast proliferation and angiogenesis. TAMs had high expression of Tgf-β, Vegf, Fgf2, Fgf10, Fgfr2 and several matrix metalloproteinases; factors that play multiple roles in supporting tumor growth, immune protection, fibroblast activation and angiogenesis.

Conclusion: Our results provide evidence that the Fgf9-induced lung adenocarcinoma is associated with recruitment and activation of M2-biased TAMs, which provided multiple means of support to the tumor. This model represents an excellent means to further study the complex interactions between TAMs, their related chemokines, and progression of lung adenocarcinoma, and adds further evidence to support the importance of TAMs in tumorigenesis.
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http://dx.doi.org/10.1016/j.lungcan.2018.02.015DOI Listing
May 2018

Ectodysplasin target gene Fgf20 regulates mammary bud growth and ductal invasion and branching during puberty.

Sci Rep 2017 07 11;7(1):5049. Epub 2017 Jul 11.

Developmental Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.

Mammary gland development begins with the appearance of epithelial placodes that invaginate, sprout, and branch to form small arborized trees by birth. The second phase of ductal growth and branching is driven by the highly invasive structures called terminal end buds (TEBs) that form at ductal tips at the onset of puberty. Ectodysplasin (Eda), a tumor necrosis factor-like ligand, is essential for the development of skin appendages including the breast. In mice, Eda regulates mammary placode formation and branching morphogenesis, but the underlying molecular mechanisms are poorly understood. Fibroblast growth factor (Fgf) receptors have a recognized role in mammary ductal development and stem cell maintenance, but the ligands involved are ill-defined. Here we report that Fgf20 is expressed in embryonic mammary glands and is regulated by the Eda pathway. Fgf20 deficiency does not impede mammary gland induction, but compromises mammary bud growth, as well as TEB formation, ductal outgrowth and branching during puberty. We further show that loss of Fgf20 delays formation of Eda-induced supernumerary mammary buds and normalizes the embryonic and postnatal hyperbranching phenotype of Eda overexpressing mice. These findings identify a hitherto unknown function for Fgf20 in mammary budding and branching morphogenesis.
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http://dx.doi.org/10.1038/s41598-017-04637-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5505952PMC
July 2017

Pulmonary fibrosis requires cell-autonomous mesenchymal fibroblast growth factor (FGF) signaling.

J Biol Chem 2017 06 9;292(25):10364-10378. Epub 2017 May 9.

the Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri 63110, and.

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive pulmonary scarring, decline in lung function, and often results in death within 3-5 five years after diagnosis. Fibroblast growth factor (FGF) signaling has been implicated in the pathogenesis of IPF; however, the mechanism through which FGF signaling contributes to pulmonary fibrosis remains unclear. We hypothesized that FGF receptor (FGFR) signaling in fibroblasts is required for the fibrotic response to bleomycin. To test this, mice with mesenchyme-specific tamoxifen-inducible inactivation of FGF receptors 1, 2, and 3 (α mice) were lineage labeled and administered intratracheal bleomycin. Lungs were collected for histologic analysis, whole lung RNA and protein, and dissociated for flow cytometry and FACS. Bleomycin-treated α mice have decreased pulmonary fibrosis, collagen production, and fewer α-smooth muscle actin-positive (αSMA+) myofibroblasts compared with controls. Freshly isolated α mesenchymal cells from bleomycin-treated mice have decreased collagen expression compared with wild type mesenchymal cells. Furthermore, lineage labeled FGFR-deficient fibroblasts have decreased enrichment in fibrotic areas and decreased proliferation. These data identify a cell autonomous requirement for mesenchymal FGFR signaling in the development of pulmonary fibrosis, and for the enrichment of the αpositive (α+) mesenchymal lineage in fibrotic tissue following bleomycin exposure. We conclude that mesenchymal FGF signaling is required for the development of pulmonary fibrosis, and that therapeutic strategies aimed directly at mesenchymal FGF signaling could be beneficial in the treatment of IPF.
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http://dx.doi.org/10.1074/jbc.M117.791764DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481550PMC
June 2017

FGF21 Regulates Metabolism Through Adipose-Dependent and -Independent Mechanisms.

Cell Metab 2017 Apr;25(4):935-944.e4

Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA; Fraternal Order of Eagles Diabetes Research Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA. Electronic address:

FGF21 is an endocrine hormone that regulates energy homeostasis and insulin sensitivity. The mechanism of FGF21 action and the tissues responsible for these effects have been controversial, with both adipose tissues and the central nervous system having been identified as the target site mediating FGF21-dependent increases in insulin sensitivity, energy expenditure, and weight loss. Here we show that, while FGF21 signaling to adipose tissue is required for the acute insulin-sensitizing effects of FGF21, FGF21 signaling to adipose tissue is not required for its chronic effects to increase energy expenditure and lower body weight. Also, in contrast to previous studies, we found that adiponectin is dispensable for the metabolic effects of FGF21 in increasing insulin sensitivity and energy expenditure. Instead, FGF21 acutely enhances insulin sensitivity through actions on brown adipose tissue. Our data reveal that the acute and chronic effects of FGF21 can be dissociated through adipose-dependent and -independent mechanisms.
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http://dx.doi.org/10.1016/j.cmet.2017.03.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5494834PMC
April 2017