Abstract
Abstract: :
Purpose: We have previously shown that connexin50 (Cx50) is absolutely required for normal postnatal lens growth. Knockout (Cx50 KO) or replacement with Cx46 by knock-in (Cx50KI46) results in smaller lenses containing fewer cells (J.Cell Biol. 143:815; Science 295:319). To determine the mechanism whereby Cx50 deficient lenses fail to grow normally, rates of cell proliferation were assayed during the period of growth failure. Methods: Wildtype, Cx50 KO and Cx50KI46 mice were injected with BrdU and lenses were dissected and fixed after one hour or 24 hours. BrdU incorporation was visualized by immunocytochemical staining and the mitotic index (MI) was determined between P0 and P7. Results: After one hour of BrdU incorporation, there was little difference in mitotic index between wildtype and Cx50 deficient lenses. For example, at P6 the wildtype 1 hour MI was 0.079 + 0.005 versus 0.081 + 0.014 in Cx50KI46 (mean + SD). In contrast, when lenses were analyzed 24 hours after BrdU injection, Cx50 deficient lenses had fewer BrdU positive cells. For example, at P6 the wildtype 24 hour MI was 0.085 + 0.019 versus 0.073 + 0.012 in Cx50 KO lenses. In addition, at 24 hours many more BrdU labeled cells appeared as pairs in the wildtype lenses than in Cx50 deficient lenses. Conclusions: These results suggest that while the initial rate of BrdU incorporation was similar in wildtype and Cx50 deficient lenses, fewer cells had completed cell division 24 hours later.
Keywords: proliferation • gap junctions/coupling • cell-cell communication