title: Further analysis of the lens phenotype in Lim2-deficient mice.
abstract: OBJECTIVE
  Lim2 (MP20) is the second most abundant integral protein of lens fiber cell membranes. A comparative analysis was performed of wild-type and Lim2-deficient (Lim2(Gt/Gt)) mouse lenses, to better define the anatomic and physiologic roles of Lim2.
  
  
  METHODS
  Scanning electron microscopy (SEM) and confocal microscopy were used to assess the contribution of Lim2 to lens tissue architecture. Differentiation-dependent changes in cytoskeletal composition were identified by mass spectrometry and immunoblot analysis. The effects on cell-cell communication were quantified using impedance analysis.
  
  
  RESULTS
  Lim2-null lenses were grossly normal. At the cellular level, however, subtle structural alterations were evident. Confocal microscopy and SEM analysis revealed that cortical Lim2(Gt/Gt) fiber cells lacked the undulating morphology that characterized wild-type fiber cells. On SDS-PAGE analysis the composition of cortical fiber cells from wild-type and Lim2-null lenses appeared similar. However, marked disparities were evident in samples prepared from the lens core of the two genotypes. Several cytoskeletal proteins that were abundant in wild-type core fiber cells were diminished in the cores of Lim2(Gt/Gt) lenses. Electrophysiological measurements indicated a small decrease in the membrane potential of Lim2(Gt/Gt) lenses and a two-fold increase in the effective intracellular resistivity. In the lens core, this may have reflected decreased expression levels of the gap junction protein connexin 46 (Cx46). In contrast, increased resistivity in the outer cell layers of Lim2(Gt/Gt) lenses could not be attributed to decreased connexin expression and may reflect the absence of cell fusions in Lim2(Gt/Gt) lenses.
  
  
  CONCLUSIONS
  Comparative analysis of wild-type and Lim2-deficient lenses has implicated Lim2 in maintenance of cytoskeletal integrity, cell morphology, and intercellular communication.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: Yanrong
authors.initials: Y
authors.lastname: Shi
authors.forename: Alicia B
authors.initials: AB
authors.lastname: De Maria
authors.forename: Huan
authors.initials: H
authors.lastname: Wang
authors.forename: Richard T
authors.initials: RT
authors.lastname: Mathias
authors.forename: Paul G
authors.initials: PG
authors.lastname: FitzGerald
authors.forename: Steven
authors.initials: S
authors.lastname: Bassnett
mesh_terms: D000818:Animals; D002386:Cataract / Q000378:metabolism / Q000473:pathology*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D017097:Electric Impedance; D004591:Electrophoresis, Polyacrylamide Gel; D005136:Eye Proteins / Q000502:physiology*; D005838:Genotype; D007908:Lens, Crystalline / Q000378:metabolism / Q000648:ultrastructure*; D013058:Mass Spectrometry; D008562:Membrane Glycoproteins / Q000502:physiology*; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D010641:Phenotype; D020543:Proteome / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D005136:Eye Proteins; C489025:Lim2 protein, mouse; D008562:Membrane Glycoproteins; D020543:Proteome