title: KGF and EGF signalling block hair follicle induction and promote interfollicular epidermal fate in developing mouse skin.
abstract: A key initial event in hair follicle morphogenesis is the localised thickening of the skin epithelium to form a placode, partitioning future hair follicle epithelium from interfollicular epidermis. Although many developmental signalling pathways are implicated in follicle morphogenesis, the role of epidermal growth factor (EGF) and keratinocyte growth factor (KGF, also known as FGF7) receptors are not defined. EGF receptor (EGFR) ligands have previously been shown to inhibit developing hair follicles; however, the underlying mechanisms have not been characterised. Here we show that receptors for EGF and KGF undergo marked downregulation in hair follicle placodes from multiple body sites, whereas the expression of endogenous ligands persist throughout hair follicle initiation. Using embryonic skin organ culture, we show that when skin from the sites of primary pelage and whisker follicle development is exposed to increased levels of two ectopic EGFR ligands (HBEGF and amphiregulin) and the FGFR2(IIIb) receptor ligand KGF, follicle formation is inhibited in a time- and dose-dependent manner. We then used downstream molecular markers and microarray profiling to provide evidence that, in response to KGF and EGF signalling, epidermal differentiation is promoted at the expense of hair follicle fate. We propose that hair follicle initiation in placodes requires downregulation of the two pathways in question, both of which are crucial for the ongoing development of the interfollicular epidermis. We have also uncovered a previously unrecognised role for KGF signalling in the formation of hair follicles in the mouse.
authors.affiliation: School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, UK.
authors.forename: Gavin D
authors.initials: GD
authors.lastname: Richardson
authors.forename: Hisham
authors.initials: H
authors.lastname: Bazzi
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Fantauzzo
authors.forename: James M
authors.initials: JM
authors.lastname: Waters
authors.forename: Heather
authors.initials: H
authors.lastname: Crawford
authors.forename: Phil
authors.initials: P
authors.lastname: Hynd
authors.forename: Angela M
authors.initials: AM
authors.lastname: Christiano
authors.forename: Colin A B
authors.initials: CA
authors.lastname: Jahoda
mesh_terms: D066258:Amphiregulin; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D066255:EGF Family of Proteins; D004791:Enzyme Inhibitors / Q000378:metabolism; D000078404:Epidermal Cells; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism*; D004817:Epidermis / Q000196:embryology; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D051526:Fibroblast Growth Factor 10 / Q000378:metabolism; D051523:Fibroblast Growth Factor 7 / Q000235:genetics / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism; D018859:Hair Follicle / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D066257:Heparin-binding EGF-like Growth Factor; D018960:Hyaluronan Receptors / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009024:Morphogenesis / Q000502:physiology; D015513:Oncogene Proteins / Q000378:metabolism; D011799:Quinazolines; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D012867:Skin / Q000033:anatomy & histology / Q000196:embryology; D053668:Syndecan-1 / Q000378:metabolism; D046509:Tissue Culture Techniques; D015534:Trans-Activators / Q000378:metabolism; D020032:Tyrphostins / Q000378:metabolism; D014738:Vibrissae / Q000033:anatomy & histology / Q000196:embryology; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism; D000071676:Zinc Finger Protein GLI1; D051176:beta Catenin / Q000378:metabolism
chemical_list: D066258:Amphiregulin; C587849:Areg protein, mouse; D015820:Cadherins; D066255:EGF Family of Proteins; D004791:Enzyme Inhibitors; C496464:Fgf10 protein, mouse; D051526:Fibroblast Growth Factor 10; D006023:Glycoproteins; C587884:Hbegf protein, mouse; D053823:Hedgehog Proteins; D066257:Heparin-binding EGF-like Growth Factor; D018960:Hyaluronan Receptors; D036341:Intercellular Signaling Peptides and Proteins; D015513:Oncogene Proteins; D011799:Quinazolines; C465570:Shh protein, mouse; D053668:Syndecan-1; D015534:Trans-Activators; D020032:Tyrphostins; D051153:Wnt Proteins; D000071676:Zinc Finger Protein GLI1; D051176:beta Catenin; D051523:Fibroblast Growth Factor 7; C101044:RTKI cpd; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D051497:Receptor, Fibroblast Growth Factor, Type 2; C065104:keratinocyte growth factor receptor