Abstract
Purpose: :
Glutaredoxin 2 (Grx2) is an enzyme with dethiolase and peroxidase activities and is present in the mitochondria where it may protect the organelle from oxidative damage and regulate its redox balances. Recently we developed a global Grx2 gene knockout (KO) mouse model with a phenotype of early age-dependent cataract development, compared with the wild type (WT) control. The purpose of this study is to examine how Grx2 gene deletion affects lens development and influence its transparency.
Methods: :
Histological slides were made using whole eye globe (5 m WT, Grx2 KO), fixed and sectioned into 5 micron thickness, followed with hematoxylin and eosin staining. Lens cryosections prepared from WT and Grx2 KO mice at 1.2 m were immunostained with the lens differentiation marker filensin, counterstained for F-actin (fluorescent-conjugated phalloidin) and nuclei (TO-PRO-3), and imaged by confocal microscopy. Filensin expression also was examined in 1, 7, and 16 m WT and KO mice by Western blot analysis.
Results: :
Lenses from Grx2 null mice showed similar growth in size and weight as WT mice but developed nuclear opacity 3 months sooner than the age-matched control. Histological section at the polar region of the Grx2 KO lens (5 m) showed heavy nuclei staining deep into the fiber cell layers. Saggital cryosections of 1.2 m-old Grx2-/- mice stained for F-actin showed a normal anterior-posterior alignment of fiber cells in the lens cortex, but cross-sectional analysis revealed patches of aberrant organization of the normal hexagonal packed structure. Immunostaining showed a lower-level expression of filensin in the cortex of Grx2-/- lenses compared to controls that was confirmed by Western blot analysis. And, unlike control lenses in which nuclei are lost with fiber cell differentiation, in the Grx2-/- lens nuclei persisted in the centermost fiber cells.
Conclusions: :
Grx2 gene deletion interferes the lens fiber differentiation and also inhibits the process of de-nucleation during lens development. Aberration of both may contribute to the early nuclear cataract formation in the Grx2-/- lens.
Keywords: transgenics/knock-outs • differentiation • cataract