Connexins are the subunit proteins of gap junctions, which allow the exchange of ions, second messengers and small metabolites between adjacent cells through intercellular channels. Gap junctional communication is important in the development and maintenance of lens, as mutations in lens connexin genes cause cataract and developmental defects in humans and mice. Signal transduction pathways have also been shown to play critical roles in lens development and homeostasis, and mutations in signaling genes like phosphatase and tensin homolog (PTEN) cause complex human syndromic disorders that include cataract. Although great progress has been made, there are still substantial gaps in our knowledge about potential cooperation between these two different intercellular communication systems. In this proposal, our objective is to further define how gap junctional communication interacts with other intercellular signal transduction pathways in the lens. We propose first to examine the consequences of PI3K deficiency by generating and characterizing conditional knockout mice lacking the p110a and p110b catalytic subunits of PI3K in the lens. Second, we will make conditional knockout mice lacking PTEN in the lens, and examine their phenotype. Finally, we will investigate interactions between lens gap junctional coupling and the PI3K/Akt and PTEN signaling pathways in postnatal growth and homeostasis by using pharmacological blockers, electrophysiological measurements and biochemical assays in vitro. We will also cross PI3K and PTEN conditional knockout animals with connexin knockout mice to confirm interactions in vivo. These studies will provide insights into how gap junctional coupling and signal transduction pathways synergistically interact to regulate lens growth and homeostasis by combining in vitro pharmacological and electrophysiological assays with in vivo animal models. They also will broaden the general paradigm of how an integrated system of intercellular communication contributes to the regulation of development in many tissues.
Mutations in connexin genes cause a broad spectrum of human health problems including cataract and ocular developmental defects in humans and mice. Mutations in phosphatase and tensin homolog (PTEN) cause a complex human syndromic disorder that includes cataract. Genetic studies have revealed much about cataract causing mutations in these different genes, but there are still substantial gaps in our knowledge about potential cooperation between these two different intercellular communication systems in preventing cataract in the normal lens. The proposed studies will further characterize these genes that cause congenital cataract, and also further characterize the control of the cell cycle in lens epithelia by integrated communication pathways.
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