title: ADAM17 transactivates EGFR signaling during embryonic eyelid closure.
abstract: OBJECTIVE
  During mammalian embryonic eyelid closure ADAM17 has been proposed to play a role as a transactivator of epidermal growth factor receptor (EGFR) signaling by shedding membrane bound EGFR ligands. However, ADAM17 also sheds numerous other ligands, thus implicating ADAM17 in additional molecular pathways. The goal of this study was to experimentally establish the role of ADAM17 and determine ADAM17-mediated pathways essential for the embryonic eyelid closure.
  
  
  METHODS
  Wild-type (WT) and woe mice, carrying a hypomorphic mutation in Adam17, were evaluated using H&E and scanning electron microscopy. Expressions of ADAM17, EGFR, and the phosphorylated form EGFR-P were evaluated using immunohistochemistry. BrdU and TUNEL assays were used to evaluate cell proliferation and apoptosis, respectively. In vitro scratch assays of primary cultures were used to evaluate cell migration. Clinical and histologic analyses established if the hypermorphic Egfr(Dsk5) allele can rescue the woe embryonic eyelid closure.
  
  
  RESULTS
  woe mice exhibited a failure to develop the leading edge of the eyelid and consequently failure of the embryonic eyelid closure. Expression of ADAM17 was identified in the eyelid epithelium in the cells of the leading edge. ADAM17 is essential for epithelial cell migration, but does not play a role in proliferation and apoptosis. EGFR was expressed in both WT and woe eyelid epithelium, but the phosphorylated EGFR-P form was detected only in WT. The Egfr(Dsk5) allele rescued woe eyelid closure defects, but also rescued woe anterior segment defects and the absence of meibomian glands.
  
  
  CONCLUSIONS
  We provide in vivo genetic evidence that the role of ADAM17 during embryonic eyelid closure is to transactivate EGFR signaling.
authors.affiliation: Department of Cell Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Eryn L
authors.initials: EL
authors.lastname: Hassemer
authors.forename: Bradley
authors.initials: B
authors.lastname: Endres
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Toonen
authors.forename: Adam
authors.initials: A
authors.lastname: Ronchetti
authors.forename: Richard
authors.initials: R
authors.lastname: Dubielzig
authors.forename: Duska J
authors.initials: DJ
authors.lastname: Sidjanin
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism*; D000072198:ADAM17 Protein; D000818:Animals; D016923:Cell Death / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D049109:Cell Proliferation; D066246:ErbB Receptors / Q000378:metabolism*; D005143:Eyelids / Q000002:abnormalities / Q000166:cytology / Q000196:embryology* / Q000378:metabolism*; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D005838:Genotype; D008024:Ligands; D008297:Male; D008537:Meibomian Glands / Q000166:cytology / Q000196:embryology / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D010641:Phenotype; D011247:Pregnancy; D061251:Primary Cell Culture; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D008024:Ligands; C541485:EGFR protein, mouse; D066246:ErbB Receptors; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606463:Adam17 protein, mouse