title: Nonselective assembly of fibrillin 1 and fibrillin 2 in the rodent ocular zonule and in cultured cells: implications for Marfan syndrome.
abstract: OBJECTIVE
  Fibrillins are the major constituent of tissue microfibrils, which form the ocular zonule. In Marfan syndrome (MFS), FBN1 mutations lead to ectopia lentis. The goal of this work was to investigate zonule composition and formation in fibrillin-deficient and wild-type mice.
  
  
  METHODS
  Immunofluorescence staining of eyes from wild-type, Fbn1-deficient, and Fbn2-deficient mice, as well as other species, was performed using monospecific fibrillin 1 and fibrillin 2 antibodies. The zonule of Fbn1-deficient and Fbn2-deficient mice was studied by electron microscopy. Microfibril formation in vitro was evaluated by immunofluorescence microscopy of cultured nonpigmented ciliary epithelial cells and fibroblasts.
  
  
  RESULTS
  A zonule was present in both Fbn1-deficient and Fbn2-deficient mouse eyes. Immunofluorescence demonstrated that the zonule of Fbn1-deficient mice, wild-type mice, rats, and hamsters contained fibrillin 2. The zonule of Fbn2(-/-) mice contained fibrillin 1. Fibrillin 1 and fibrillin 2 colocalized in microfibrils formed in human nonpigmented ciliary epithelium cultures. Like fibrillin 1, fibrillin 2 microfibril assembly was fibronectin dependent and initiated by cell surface punctate deposits that elongated to form microfibrils.
  
  
  CONCLUSIONS
  These data suggest that fibrillin 1 assembly and fibrillin 2 assembly share similar mechanisms. Microfibril composition depends substantially on the local levels of fibrillin isoforms and is not highly selective in regard to the isoform. This raises the intriguing possibility that the zonule could be strengthened in MFS by inducing fibrillin 2 expression in ciliary epithelium. The presence of fibrillin 2 in the murine zonule and an intact zonule in Fbn1-knockout mice may limit the utility of rodent models for studying ectopia lentis in MFS.
authors.affiliation: Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio.
authors.forename: Lauren C
authors.initials: LC
authors.lastname: Beene
authors.forename: Lauren W
authors.initials: LW
authors.lastname: Wang
authors.forename: Dirk
authors.initials: D
authors.lastname: Hubmacher
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Keene
authors.forename: Dieter P
authors.initials: DP
authors.lastname: Reinhardt
authors.forename: Douglas S
authors.initials: DS
authors.lastname: Annis
authors.forename: Deane F
authors.initials: DF
authors.lastname: Mosher
authors.forename: Robert P
authors.initials: RP
authors.lastname: Mecham
authors.forename: Elias I
authors.initials: EI
authors.lastname: Traboulsi
authors.forename: Suneel S
authors.initials: SS
authors.lastname: Apte
mesh_terms: D000368:Aged; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002924:Ciliary Body / Q000166:cytology / Q000378:metabolism*; D006224:Cricetinae; D004479:Ectopia Lentis / Q000378:metabolism / Q000517:prevention & control; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism; D000071838:Fibrillin-1; D000071840:Fibrillin-2; D000071837:Fibrillins; D005347:Fibroblasts / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D015870:Gene Expression; D015316:Genetic Therapy; D006801:Humans; D007908:Lens, Crystalline / Q000378:metabolism*; D008022:Ligaments / Q000378:metabolism* / Q000648:ultrastructure; D008382:Marfan Syndrome / Q000378:metabolism / Q000517:prevention & control*; D008647:Mesocricetus; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020894:Microfibrils / Q000378:metabolism / Q000648:ultrastructure; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D051381:Rats; D017207:Rats, Sprague-Dawley; D054392:Adipokines
chemical_list: D000071838:Fibrillin-1; D000071840:Fibrillin-2; D000071837:Fibrillins; D008840:Microfilament Proteins; C000605722:FBN1 protein, human; D054392:Adipokines; C000605723:FBN2 protein, human; C000605724:Fbn1 protein, mouse; C000605725:Fbn1 protein, rat; C000605728:Fbn2 protein, mouse; C000605729:Fbn2 protein, rat
keywords: Marfan syndrome; fibrillin; zonule