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J. Cell Biol.,
Volume 143, Number 3, November 2, 1998 815-825
Department of Cell Biology and Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115
In the ocular lens, gap junctional communication is a key component of homeostatic mechanisms
preventing cataract formation. Gap junctions in rodent
lens fibers contain two known intercellular channel-forming proteins, connexin50 (Cx50) and Cx46. Since
targeted ablation of Cx46 has been shown to cause senile-type nuclear opacities, it appears that Cx50 alone
cannot meet homeostatic requirements. To determine
if lens pathology arises from a reduction in levels of
communication or the loss of a connexin-specific function, we have generated mice with a targeted deletion
of the Cx50 gene. Cx50-null mice exhibited microphthalmia and nuclear cataracts. At postnatal day 14 (P14), Cx50-knockout eyes weighed 32% less than controls, whereas lens mass was reduced by 46%. Cx50-knockout lenses also developed zonular pulverulent
cataracts, and lens abnormalities were detected by P7.
Deletion of Cx50 did not alter the amounts or distributions of Cx46 or Cx43, a component of lens epithelial
junctions. In addition, intercellular passage of tracers revealed the persistence of communication between all
cell types in the Cx50-knockout lens. These results
demonstrate that Cx50 is required not only for maintenance of lens transparency but also for normal eye
growth. Furthermore, these data indicate that unique
functional properties of both Cx46 and Cx50 are required for proper lens development.
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