Gap junction expression and lens morphology in connexin43 (Cx43) knockout (KO) mice

Purpose. To investigate gap junction expression in lens and the role of gap junction protein Cx43 in controlling lens development and organization. Methods. We used mice in which the Cx43 gene was disrupted by homologous recombination (Reaume et al., Science 267: 1831, 1995). These mice die at birth due to right ventricular outflow tract obstruction. Lenses from Cx43 KO mice and wildtype littermates were used as follows: (1) 2% glutaraldehyde fixation for light and transmission electron microscopy; and (2) freezing in liquid nitrogen for light and confocal microscopy of immunofluorescence in cryosections. Results. In wildtype animals, Cx43 was immunolocalized to apical and lateral regions of lens epithelial cells and throughout the corneum, primarily at lateral regions of epithelial cells but also within the stroma. Ultrastructural studies revealed that epithelial cells were connected to one another by large areas of gap junctional contact; lens fiber cells were closely apposed to apical boundaries of epithelial cells and to one another along their entire lengths. In Cx43 KO animals, in which Cx43 immunoreactivity was totally absent, tiny regions of apparent gap junctional contact were still seen between epithelial cells, suggesting that another gap junction protein might contribute to these junctions. Organization of appositional membranes between lens fiber cells and between fiber and epithelial cells differed dramatically in the Cx43 KO lens. Between fiber cells, large vacuolar spaces appeared, and fiber cells were largely separated from apical surfaces of epithelial cells. Conclusions. These results indicate that lenses of Cx43 KO mice exhibit histological features typical of cataract, thereby providing evidence that these gap junctions play a critical role in determining the normal close packing of lens cell membranes that typifies this tissue.