Biomedical subjects

Saverio Bellusci

Publications and source records attributed to Saverio Bellusci.

At least 19 recordsLinked to original sources

PubMed2006

Fibroblast growth factor 10 is required for survival and proliferation but not differentiation of intestinal epithelial progenitor cells during murine colon development.

Epithelial-mesenchymal interactions that govern the development of the colon from the primitive gastrointestinal tract are still unclear. In this study, we determine the temporal-spatial expression pattern of Fibroblast growth factor 10 (Fgf10), a key developmental gene, in the colon at different developmental stages. We found that Fgf10 is expressed in the mesenchyme of the distal colon, while its main receptor Fgfr2-IIIb is expressed throughout the entire intestinal epithelium. We demonstrate that Fgf10 inactivation leads to decreased proliferation and increased cell apoptosis in the colonic epithelium at E10.5, therefore resulting in distal colonic atresia. Using newly described Fgf10 hypomorphic mice, we show that high levels of FGF10 are dispensable for the differentiation of the colonic epithelium. Our work unravels for the first time the pivotal role of FGF10 in the survival and proliferation of the colonic epithelium, biological activities which are essential for colonic crypt formation.

Animals↗

PubMed2006

Levels of mesenchymal FGFR2 signaling modulate smooth muscle progenitor cell commitment in the lung.

Fibroblast growth factor (FGF) signaling has been shown to regulate lung epithelial development but its influence on mesenchymal differentiation has been poorly investigated. To study the role of mesenchymal FGF signaling in the differentiation of the mesenchyme and its impact on epithelial morphogenesis, we took advantage of Fgfr2c(+/Delta) mice, which due to a splicing switch express Fgfr2b in mesenchymal tissues and manifest Apert syndrome-like phenotypes. Using a set of in vivo and in vitro studies, we show that an autocrine FGF10-FGFR2b signaling loop is established in the mutant lung mesenchyme, which has several consequences. It prevents the entry of the smooth muscle progenitors into the smooth muscle cell (SMC) lineage and results in reduced fibronectin and elastin deposition. Levels of Fgf10 expression are raised within the mutant mesenchyme itself. Epithelial branching as well as epithelial levels of FGF and canonical Wnt signaling is dramatically reduced. These defects result in arrested development of terminal airways and an "emphysema like" phenotype in postnatal lungs. Our work unravels part of the complex interactions that govern normal lung development and may be pertinent to understanding the basis of respiratory defects in Apert syndrome.

Animals↗

PubMed2006

The fibroblast growth factor pathway serves a regulatory role in proliferation and apoptosis in the pathogenesis of intestinal atresia.

BACKGROUND/PURPOSE: Intestinal atresia occurs in 1:5000 live births and is a neonatal challenge. Fibroblast growth factor receptor 2b (Fgfr2b) is a critical developmental regulator of proliferation and apoptosis in multiple organ systems including the gastrointestinal tract (GIT). Fgfr2b invalidation results in an autosomal recessive intestinal atresia phenotype. This study evaluates the role of Fgfr2b signaling in regulating proliferation and apoptosis in the pathogenesis of intestinal atresia. METHODS: Wild-type and Fgfr2b-/- embryos were harvested from timed pregnant mice. The GIT was harvested using standard techniques. Terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling) was used to evaluate apoptosis and bromodeoxyuridine to assess proliferation by standard protocols. Photomicrographs were compared (Institutional Animal Care and Use Committee-approved protocol 32-02). RESULTS: Wild-type and mutant GIT demonstrate that deletion of the Fgfr2b gene results in inhibition of epithelial proliferation and increased apoptosis. Inhibited proliferation and increased apoptosis are specific to those tissues of normal Fgfr2b expression, corresponding to the site of intestinal atresia. CONCLUSIONS: The absence of embryonic GIT Fgfr2b expression results in decreased proliferation and increased apoptosis resulting in GIT atresia. The regulation of proliferation and apoptosis in intestinal cells as a genetically based cause of intestinal atresia represents a novel consideration in the pathogenesis of intestinal atresia.

Animals↗

PubMed2006

Stomach development is dependent on fibroblast growth factor 10/fibroblast growth factor receptor 2b-mediated signaling.

BACKGROUND & AIMS: Fibroblast growth factors (Fgfs) and their receptors (Fgfrs) are important intercellular signaling molecules that are essential to mammalian embryonic development. The signaling pathways between endoderm-derived gastric epithelium and the surrounding mesenchyme are largely unknown; however, the developmental expression profile of the IIIb isoform of Fgfr2 (Fgfr2b) and its main ligand, Fgf10, suggest that they may be strong candidates. Mice lacking either component (Fgfr2b-/- or Fgf10-/-) were examined to determine the role of Fgfr2b-mediated signaling during gastric organogenesis. METHODS: Stomachs from embryonic day 13.5-18.5 Fgfr2b-/-, Fgf10-/-, and wild-type littermates were collected and analyzed by conventional histology, immunohistochemistry, in situ hybridization, and electron microscopy. RESULTS: Fgfr2b-/- and Fgf10-/- fetuses had stomachs smaller than wild-type, consisting of relatively proportionate forestomach but disproportionately reduced glandular stomach, the mucosa of which has low cytoarchitectural complexity with a spiral arrangement of large mucosal folds. During mid to late fetal stages (embryonic day 15.5-18.5), epithelial differentiation to mucous and chief cell lineages was rudimentary, with no expression of several early cytodifferentiation markers including GATA4, GATA6, and H+/K+-adenosine triphosphatase and abnormal expression of members of the hedgehog family of signaling molecules. CONCLUSIONS: Fgfr2b and Fgf10 are part of a signaling network with Sonic hedgehog and Indian hedgehog that are essential to anterior-posterior and radial patterning in gastric development.

Animals↗

PubMed2006

Gli3-mediated somitic Fgf10 expression gradients are required for the induction and patterning of mammary epithelium along the embryonic axes.

Little is known about the regulation of cell fate decisions that lead to the formation of five pairs of mammary placodes in the surface ectoderm of the mouse embryo. We have previously shown that fibroblast growth factor 10 (FGF10) is required for the formation of mammary placodes 1, 2, 3 and 5. Here, we have found that Fgf10 is expressed only in the somites underlying placodes 2 and 3, in gradients across and within these somites. To test whether somitic FGF10 is required for the formation of these two placodes, we analyzed a number of mutants with different perturbations of somitic Fgf10 gradients for the presence of WNT signals and ectodermal multilayering, markers for mammary line and placode formation. The mammary line is displaced dorsally, and formation of placode 3 is impaired in Pax3ILZ/ILZ mutants, which do not form ventral somitic buds. Mammary line formation is impaired and placode 3 is absent in Gli3Xt-J/Xt-J and hypomorphic Fgf10 mutants, in which the somitic Fgf10 gradient is shortened dorsally and less overall Fgf10 is expressed, respectively. Recombinant FGF10 rescued mammogenesis in Fgf10(-/-) and Gli3Xt-J/Xt-J flanks. We correlate increasing levels of somitic FGF10 with progressive maturation of the surface ectoderm, and show that full expression of somitic Fgf10, co-regulated by GLI3, is required for the anteroposterior pattern in which the flank ectoderm acquires a mammary epithelial identity. We propose that the intra-somitic Fgf10 gradient, together with ventral elongation of the somites, determines the correct dorsoventral position of mammary epithelium along the flank.

Animals↗

PubMed2006

Lung development and susceptibility to chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease with emphysema has been considered to be an accelerated involutional disease of aging smokers. However, because only a proportion ( approximately 15%) of smokers develop chronic obstructive pulmonary disease with emphysema, clearly genetic susceptibility must play a significant part in determining both the age of onset and the rapidity of decline in lung function. In mice, interference with key genes, either by null mutation, hypomorphism, or gain or loss of function, results in phenotypes comprising either neonatal lethal respiratory distress if the structural effect is severe, or reduced alveolarization and/or early-onset emphysema if the effect is milder. Likewise, null mutants that interfere with matrix assembly and/or integrity, such as elastin, lysyl oxidase, or fibrillin, also result in alveolar dysplasia. Importantly, null mutation of Smad3, which encodes a receptor-activated Smad in the transforming growth factor-beta signaling pathway, results in a more subtle failure to correctly organize the alveolar matrix, which is in turn antecedent to early-onset emphysema mediated by matrix metalloproteinase-9. Furthermore, exposure to side-stream smoke profoundly exacerbates and accelerates alveolar destruction, leading to more severe early-onset emphysema in young Smad3-null mice (unpublished data). Interestingly, polymorphisms in the fibrillin, transforming growth factor-beta type II receptor, and matrix metalloproteinase-9 genes have been described in humans with emphysema. Thus, dysplastic or degraded matrix cannot provide the structural niche for alveolar stem/progenitor cells to assume the correct phenotype and/or repair the alveolar cell lineage niche. The hope is that providing the correct exogenous signals can coax them into doing so.

Age Factors↗

PubMed2005

Wnt5a regulates Shh and Fgf10 signaling during lung development.

The role of WNT signaling and its interactions with other morphogenetic pathways were investigated during lung development. Previously, we showed that targeted disruption of Wnt5a results in over-branching of the epithelium and thickening of the interstitium in embryonic lungs. In this study, we generated and characterized transgenic mice with lung-specific over-expression of Wnt5a from the SpC promoter. Over-expression of Wnt5a interfered with normal epithelial-mesenchymal interactions resulting in reduced epithelial branching and dilated distal airways. During early lung development, over-expression of Wnt5a in the epithelium resulted in increased Fgf10 in the mesenchyme and decreased Shh in the epithelium. Both levels and distribution of SHH receptor, Ptc were reduced in SpC-Wnt5a transgenic lungs and were reciprocally correlated to changes of Fgf10 in the mesenchyme, suggesting that SHH signaling is decreased by over-expression of Wnt5a. Cultured mesenchyme-free epithelial explants from SpC-Wnt5a transgenic lungs responded abnormally to recombinant FGF10 supplied uniformly in the Matrigel with dilated branch tips that mimic the in vivo phenotype. In contrast, chemotaxis of transgenic epithelial explants towards a directional FGF10 source was inhibited. These suggest that over-expression of Wnt5a disrupts epithelial-response to FGF10. In conclusion, Wnt5a regulates SHH and FGF10 signaling during lung development.

Animals↗

PubMed2005

FGF10/FGFR2b signaling plays essential roles during in vivo embryonic submandibular salivary gland morphogenesis.

BACKGROUND: Analyses of Fgf10 and Fgfr2b mutant mice, as well as human studies, suggest that FGF10/FGFR2b signaling may play an essential, nonredundant role during embryonic SMG development. To address this question, we have analyzed the SMG phenotype in Fgf10 and Fgfr2b heterozygous and null mutant mice. In addition, although previous studies suggest that the FGF10/FGFR2b and FGF8/FGFR2c signaling pathways are functionally interrelated, little is known about the functional relationship between these two pathways during SMG development. We have designed in vivo and in vitro experiments to address this question. RESULTS: We analyzed Fgf10 and Fgfr2b heterozygous mutant and null mice and demonstrate dose-dependent SMG phenotypic differences. Hypoplastic SMGs are seen in Fgf10 and Fgfr2b heterozygotes whereas SMG aplasia is seen in Fgf10 and Fgfr2b null embryos. Complementary in vitro studies further indicate that FGF10/FGFR2b signaling regulates SMG epithelial branching and cell proliferation. To delineate the functional relationship between the FGF10/FGFR2b and FGF8/FGFR2c pathways, we compared the SMG phenotype in Fgfr2c+/Delta/Fgf10+/- double heterozygous mice to that seen in wildtype, Fgf10+/- (Fgfr2c+/+/Fgf10+/-) and Fgfr2c+/Delta (Fgfr2c+/Delta/Fgf10+/+) single heterozygous mutant littermates and demonstrate genotype-specific SMG phenotypes. In addition, exogenous FGF8 was able to rescue the abnormal SMG phenotype associated with abrogated FGFR2b signaling in vitro and restore branching to normal levels. CONCLUSION: Our data indicates that FGF10/FGFR2b signaling is essential for the SMG epithelial branching and histodifferentiation, but not earliest initial bud formation. The functional presence of other endogenous signaling pathways could not prevent complete death of embryonic SMG cells in Fgf10 and Fgfr2b null mice. Though we were able to rescue the abnormal phenotype associated with reduced in vitro FGF10/FGFR2b signaling with exogenous FGF8 supplementation, our results indicate that the FGF10/FGFR2b and FGF8/FGFR2c are nonredundant signaling pathways essential for in vivo embryonic SMG development. What remains to be determined is the in vivo functional relationship between the FGF10/FGFR2b signal transduction pathway and other key signaling pathways, and how these pathways are integrated during embryonic SMG development to compose the functional epigenome.

Animals↗

PubMed2005

A novel function for the protein tyrosine phosphatase Shp2 during lung branching morphogenesis.

Branching morphogenesis of many organs, including the embryonic lung, is a dynamic process in which growth factor mediated tyrosine kinase receptor activation is required, but must be tightly regulated to direct ramifications of the terminal branches. However, the specific regulators that modulate growth factor signaling downstream of the tyrosine kinase receptor remain to be determined. Herein, we demonstrate for the first time an important function for the intracellular protein tyrosine phosphatase Shp2 in directing embryonic lung epithelial morphogenesis. We show that Shp2 is specifically expressed in embryonic lung epithelial buds, and that loss of function by the suppression of Shp2 mRNA expression results in a 53% reduction in branching morphogenesis. Furthermore, by intra-tracheal microinjection of a catalytically inactive adenoviral Shp2 construct, we provide direct evidence that the catalytic activity of Shp2 is required for proper embryonic lung branch formation. We demonstrate that Shp2 activity is required for FGF10 induced endodermal budding. Furthermore, a loss of Shp2 catalytic activity in the embryonic lung was associated with a reduction in ERK phosphorylation and epithelial cell proliferation. However, epithelial cell differentiation was not affected. Our results show that the protein tyrosine phosphatase Shp2 plays an essential role in modulating growth factor mediated tyrosine kinase receptor activation in early embryonic lung branching morphogenesis.

Adenoviridae↗

PubMed2005

Molecular mechanisms of early lung specification and branching morphogenesis.

The "hard wiring" encoded within the genome that determines the emergence of the laryngotracheal groove and subsequently early lung branching morphogenesis is mediated by finely regulated, interactive growth factor signaling mechanisms that determine the automaticity of branching, interbranch length, stereotypy of branching, left-right asymmetry, and finally gas diffusion surface area. The extracellular matrix is an important regulator as well as a target for growth factor signaling in lung branching morphogenesis and alveolarization. Coordination not only of epithelial but also endothelial branching morphogenesis determines bronchial branching and the eventual alveolar-capillary interface. Improved prospects for lung protection, repair, regeneration, and engineering will depend on more detailed understanding of these processes. Herein, we concisely review the functionally integrated morphogenetic signaling network comprising the critical bone morphogenetic protein, fibroblast growth factor, Sonic hedgehog, transforming growth factor-beta, vascular endothelial growth factor, and Wnt signaling pathways that specify and drive early embryonic lung morphogenesis.

Animals↗

PubMed2005

Fgf10 expression identifies parabronchial smooth muscle cell progenitors and is required for their entry into the smooth muscle cell lineage.

Lineage formation in the lung mesenchyme is poorly understood. Using a transgenic mouse line expressing LacZ under the control of Fgf10 regulatory sequences, we show that the pool of Fgf10-positive cells in the distal lung mesenchyme contains progenitors of the parabronchial smooth muscle cells. Fgf10 gene expression is slightly repressed in this transgenic line. This allowed us to create a hypomorphic Fgf10 phenotype by expressing the LacZ transgene in a heterozygous Fgf10 background. Hypomorphic Fgf10 mutant lungs display a decrease in beta-galactosidase-positive cells around the bronchial epithelium associated with an accumulation of beta-galactosidase-expressing cells in the distal mesenchyme. This correlates with a marked reduction of alpha smooth muscle actin expression, thereby demonstrating that FGF10 is mostly required for the entry of mesenchymal cells into the parabronchial smooth muscle cell lineage. The failure of exogenous FGF10 to phosphorylate its known downstream targets ERK and AKT in lung mesenchymal cultures strongly suggests that FGF10 acts indirectly on the progenitor population via an epithelial intermediate. We provide support for a role of epithelial BMP4 in mediating the formation of parabronchial smooth muscle cells.

Actins↗

PubMed2005

Protein interaction mapping: a Drosophila case study.

The Drosophila (fruit fly) model system has been instrumental in our current understanding of human biology, development, and diseases. Here, we used a high-throughput yeast two-hybrid (Y2H)-based technology to screen 102 bait proteins from Drosophila melanogaster, most of them orthologous to human cancer-related and/or signaling proteins, against high-complexity fly cDNA libraries. More than 2300 protein-protein interactions (PPI) were identified, of which 710 are of high confidence. The computation of a reliability score for each protein-protein interaction and the systematic identification of the interacting domain combined with a prediction of structural/functional motifs allow the elaboration of known complexes and the identification of new ones. The full data set can be visualized using a graphical Web interface, the PIMRider (http://pim.hybrigenics.com), and is also accessible in the PSI standard Molecular Interaction data format. Our fly Protein Interaction Map (PIM) is surprisingly different from the one recently proposed by Giot et al. with little overlap between the two data sets. Analysis of the differences in data sets and methods suggests alternative strategies to enhance the accuracy and comprehensiveness of the post-genomic generation of broad-scale protein interaction maps.

Animals↗

PubMed2005

Dickkopf-1 (DKK1) reveals that fibronectin is a major target of Wnt signaling in branching morphogenesis of the mouse embryonic lung.

Members of the Dickkopf (Dkk) family of secreted proteins are potent inhibitors of Wnt/beta-catenin signaling. In this study we show that Dkk1, -2, and -3 are expressed distally in the epithelium, while Kremen1, the needed co-receptor, is expressed throughout the epithelium of the developing lung. Using TOPGAL mice [DasGupta, R., Fuchs, E., 1999. Multiple roles for activated LEF/TCF transcription complexes during hair follicle development and differentiation. Development 126, 4557-4568] to monitor the Wnt pathway, we show that canonical Wnt signaling is dynamic in the developing lung and is active throughout the epithelium and in the proximal smooth muscle cells (SMC) until E12.5. However, from E13.5 onwards, TOPGAL activity is absent in the SMC and is markedly reduced in the distal epithelium coinciding with the onset of Dkk-1 expression in the distal epithelium. To determine the role of Wnt signaling in early lung development, E11.5 organ cultures were treated with recombinant DKK1. Treated lungs display impaired branching, characterized by failed cleft formation and enlarged terminal buds, and show decreased alpha-smooth muscle actin (alpha-SMA) expression as well as defects in the formation of the pulmonary vasculature. These defects coincide with a pattern of decreased fibronectin (FN) deposition. DKK1-induced morphogenetic defects can be mimicked by inhibition of FN and overcome by addition of exogenous FN, suggesting an involvement of FN in Wnt-regulated morphogenetic processes.

Actins↗

PubMed2005

Colonic atresia without mesenteric vascular occlusion. The role of the fibroblast growth factor 10 signaling pathway.

BACKGROUND/PURPOSE: Colonic atresia occurs in 1:20,000 live births, offering a neonatal surgical challenge. Prenatal expression of fibroblast growth factor 10 (Fgf10), acting through fibroblast growth factor receptor 2b (Fgfr2b), is critical to the normal development of the colon. Invalidation of the Fgf10 pathway results in colonic atresia, inherited in an autosomal recessive pattern. Classically, disturbance of the mesenteric vasculature has been thought to cause many forms of intestinal atresia. The purpose of this study was to evaluate the role of vascular occlusion in the pathogenesis of colonic atresia. METHODS: Wild type (Wt), Fgf10(-/-), and Fgfr2b(-/-) mutant mouse embryos were harvested from timed pregnant mothers. Immediately following harvest, filtered India ink was infused via intracardiac microinjection. The gastrointestinal tract was dissected, and photomicrographs of the mesenteric arterial anatomy were taken at key developmental time points. RESULTS: Photomicrographs after India ink microinjections demonstrate normal, patent mesenteric cascades to the atretic colon at the time points corresponding to the failure of colonic development in the Fgf10(-/-) and Fgfr2b(-/-) mutants. The mesenteric arterial anatomy of the colon demonstrates no difference between the Wt and mutant colonic atresia. CONCLUSIONS: The absence of embryonic expression of Fgf10 or its receptor Fgfr2b results in colonic atresia in mice. India ink microinjection is a direct measure of mesenteric arterial patency. Colonic atresia in the Fgf10(-/-) and Fgfr2b(-/-) mutants occurs despite normal mesenteric vascular development. Thus the atresia is not the result of a mesenteric vascular occlusion. The patent colonic mesentery of the Fgf10(-/-) and Fgfr2b(-/-) mutants challenges an accepted pathogenesis of intestinal atresia. Although colonic atresia can occur as a result of vascular occlusion, new evidence exists to suggest that a genetic mechanism may play a role in the pathogenesis of this disease.

Animals↗

PubMed2005

Fibroblast growth factor-10 serves a regulatory role in duodenal development.

PURPOSE: Duodenal obstruction occurs in 1 of 6000 live births and requires urgent surgical intervention. Duodenal atresia previously has been ascribed to a developmental failure of luminal recanalization; however, the cause of duodenal atresia remains incompletely understood. Although familial intestinal atresias have been described and syndromic associations are known, no specific genetic link has been established. Fibroblast growth factor-10 (Fgf10) is a known regulatory molecule relevant to mesenchymal-epithelial interactions, and mice deficient in Fgf10 demonstrate congenital anomalies in several organ systems including the gastrointestinal tract. The authors hypothesized that Fgf10 could serve a regulatory role in establishing normal duodenal development. METHODS: Wild-type mice with beta-galactosidase under the control of the Fgf10 promoter were harvested from timed-pregnancy mothers. The expression of Fgf10 in the duodenum during development was evaluated by developing the embryos in X-Gal solution. Wild-type and mutant Fgf10(-/-) embryos were harvested from timed-pregnancy mothers at 18.5 days postconception (near term) and were analyzed for duodenal morphology (Institutional Animal Care and Use Committee-approved protocol 32-02). Photomicrographs were reviewed. RESULTS: Fibroblast growth factor-10 is active in the duodenum at a late stage of development. The Fgf10(-/-) mutants demonstrate duodenal atresia with a variable phenotype similar to clinical findings. The duodenum fails to develop luminal continuity and has proximal dilation. The phenotype occurs in an autosomal recessive pattern with incomplete penetrance (38%). CONCLUSIONS: Fibroblast growth factor-10 serves as a regulator in normal duodenal growth and development. Its deletion leads to duodenal atresia and challenges traditionally accepted theories of pathogenesis. This novel, genetically mediated duodenal malformation reflects an animal model that will allow further evaluation of the pathogenesis of this surgically correctable disease. By studying the mechanism of Fgf10 function in foregut development, the authors hope to better understand these anomalies and to explore possible therapeutic alternatives.

Animals↗

PubMed2004

Genomic structure and promoter characterization of the human Sprouty4 gene, a novel regulator of lung morphogenesis.

The expression of Sprouty4 (Spry4), an intracellular FGF receptor antagonist, shows a temporally and spatially restricted pattern in embryonic lung and is induced by ERK signaling. To clarify the molecular mechanisms regulating Spry4 transcription, the genomic structure of the human Sprouty4 (hSpry4) gene was first determined by using the GenomeWalker kit. The hSpry4 gene spans > 14 kb and is organized in three exons and two introns. Multiple transcription start sites were subsequently mapped by 5'-rapid amplification of cDNA ends. Analysis of up to 4 kb of sequence in the 5'-flanking region of the gene showed the presence of multiple potential transcription factor binding sites but no TATA or CAAT boxes. Transient transfection using luciferase reporter gene constructs with progressive deletions of the hSpry4 5'-flanking region revealed that the core promoter activity is located within the proximal 0.4-kb region, whereas the minimal ERK-inducible promoter activity is between -69 and -31. Homology analysis further showed that the core promoter region of the hSpry4 gene exhibits significant similarity to the 5'-flanking region of the mouse gene.

Animals↗

PubMed2004

Identification of the mammary line in mouse by Wnt10b expression.

Mammogenesis in rabbit, rat, and human begins with the formation of an elevated ectodermal ridge in the embryo. Attempts to demonstrate a morphologically or histologically equivalent mammary line in the mouse have yielded controversial results. We show here that a mammary line exists in the mouse embryo at embryonic day (E) 11.25 as a concise line of Wnt10b expression and a broader band of Wnt6 expression in the surface ectoderm, between the subaxillary and suprainguinal region of each flank. Additional streaks of Wnt10b expression in the axillary and inguinal region join the mammary line on the flank slightly later. Expression of Wnt10b and Wnt6 becomes restricted to the placodes within 1.5 days. The ectoderm of the mammary line is organized as a pseudostratified epithelium connecting the developing mammary placodes at around E11.5, whereas all other surface ectoderm is single-layered. Thus, the mammary line expressing Wnt10b defines a distinct ectodermal region that we consider the equivalent of the ectodermal ridge in, for example, rabbit. To date, the formation of the mammary line expressing Wnt10b is the earliest discernible ectodermal event in murine embryonic mammary gland development.

Animals↗

PubMed2004

Fibroblast growth factor 10 (Fgf10) invalidation results in anorectal malformation in mice.

BACKGROUND/PURPOSE: Anorectal malformations occur in 1 per 4,000 live births and represent a surgical challenge. Although critically important, the basic mechanisms of normal anorectal union are incompletely understood. Fgf10 signaling is known to serve a key role in mesenchymal/epithelial interactions in many organ systems including the gastrointestinal tract (GIT). The authors therefore hypothesized that Fgf10 signaling has a central role in normal anorectal development. METHODS: Fgf10 expression in wild-type (Wt) embryos was evaluated using whole-mount in situ hybridization. Wt and Fgf10-/- embryos were harvested from timed pregnant mothers at E12.5 through E17.5 and were analyzed for anorectal phenotype. RESULTS: Wt development of union between anorectal structures is completed between E12.5 and E13.5 with luminal communication between distal rectal epithelium and anus. Fgf10 is discretely expressed at E12.5 in the distal rectum. Fgf10-/- mutants show failure of union of the rectum and anus at an early stage (E13.5) and near term (E17.5). CONCLUSIONS: Fgf10 is expressed in the rectum at the time when anorectal continuity is established, indicating a role in normal anorectal development. Fgf10 invalidation (Fgf10-/- mutant) results in a genetically reproducible anorectal malformation phenotype. Fgf10 function is critical for normal anorectal development.

Anal Canal↗