title: Rap1 GTPase is required for mouse lens epithelial maintenance and morphogenesis.
abstract: Rap1, a Ras-like small GTPase, plays a crucial role in cell-matrix adhesive interactions, cell-cell junction formation, cell polarity and migration. The role of Rap1 in vertebrate organ development and tissue architecture, however, remains elusive. We addressed this question in a mouse lens model system using a conditional gene targeting approach. While individual germline deficiency of either Rap1a or Rap1b did not cause overt defects in mouse lens, conditional double deficiency (Rap1 cKO) prior to lens placode formation led to an ocular phenotype including microphthalmia and lens opacification in embryonic mice. The embryonic Rap1 cKO mouse lens exhibited striking defects including loss of E-cadherin- and ZO-1-based cell-cell junctions, disruption of paxillin and β1-integrin-based cell adhesive interactions along with abnormalities in cell shape and apical-basal polarity of epithelium. These epithelial changes were accompanied by increased levels of α-smooth muscle actin, vimentin and N-cadherin, and expression of transcriptional suppressors of E-cadherin (Snai1, Slug and Zeb2), and a mesenchymal metabolic protein (Dihydropyrimidine dehydrogenase). Additionally, while lens differentiation was not overtly affected, increased apoptosis and dysregulated cell cycle progression were noted in epithelium and fibers in Rap1 cKO mice. Collectively these observations uncover a requirement for Rap1 in maintenance of lens epithelial phenotype and morphogenesis.
authors.affiliation: Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA.
authors.forename: Rupalatha
authors.initials: R
authors.lastname: Maddala
authors.affiliation: Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA.
authors.forename: Tharkika
authors.initials: T
authors.lastname: Nagendran
authors.affiliation: The Visual System Group, Division of Pediatric Ophthalmology and Developmental Biology, Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, OH 45229, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Lang
authors.affiliation: Virginia Tech Carilion Research Institute, Roanoke, VA 24016, USA.
authors.forename: Alexei
authors.initials: A
authors.lastname: Morozov
authors.affiliation: Department of Ophthalmology, Duke University School of Medicine, Durham, NC 27710, USA; Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, NC 27710, USA. Electronic address: p.rao@dm.duke.edu.
authors.forename: Ponugoti V
authors.initials: PV
authors.lastname: Rao
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000235:genetics; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002386:Cataract / Q000235:genetics; D002448:Cell Adhesion / Q000235:genetics* / Q000502:physiology; D002450:Cell Communication / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D002462:Cell Membrane / Q000378:metabolism; D016764:Cell Polarity / Q000235:genetics; D042943:Dihydrouracil Dehydrogenase (NADP) / Q000096:biosynthesis; D019573:Epithelium, Corneal / Q000196:embryology* / Q000378:metabolism; D019012:Integrin beta1 / Q000378:metabolism; D007908:Lens, Crystalline / Q000196:embryology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008850:Microphthalmos / Q000235:genetics; D051419:Paxillin / Q000378:metabolism; D019108:Tight Junctions / Q000378:metabolism*; D014746:Vimentin / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000235:genetics*
chemical_list: D000199:Actins; D015820:Cadherins; D019012:Integrin beta1; D051419:Paxillin; D014746:Vimentin; D042943:Dihydrouracil Dehydrogenase (NADP); D020827:rap1 GTP-Binding Proteins
keywords: Cell adhesion; Epithelial plasticity; Lens morphogenesis; Polarity; Rap1 GTPase