Gap junctions contain channels for the movement of molecular information between cells. These channels are formed by the assembly of products of the gap junction genes called connexins. Communication between cells via these channels provides a mechanism for transferring small molecules that can regulate and synchronize the activities of cells in specialized multi-cellular systems such as the eye lens. Gap junctional communication has been well documented for some time as an important property between cells in the eye lens. Recently, the PI has targeted the disruption of one of the gap junction genes, a3 connexin, that is preferentially expressed in lens fibers using ES cell technology and mouse embryos. This experimental procedure has resulted in the development of an a3 connexin knockout mouse that contains a lens opacity resembling the human age-dependent nuclear cataract phenotype. Thus, this analysis has provided the first direct evidence for an important role for gap junctions in the physiology of the lens. The long term objective of this project is to understand how alterations in the gap junctional communication pathway that result from disruption of a connexin gene contribute to the formation of a cataract. The analysis will include the further characterization of the animal with the knockout of the a3 connexin gene, as well as the generation of an animal with a disruption of another connexin gene, a8, that is used by lens fiber cells. Once both knockout animals have been generated, homozygote mice containing knockouts of both a3 and a8 connexin genes will be analyzed. The connexin knockout mice will be extensively characterized to determine both morphological and biochemical changes that have taken place that contribute to the observed phenotypes. In addition, an experimental strategy will be applied to try and rescue the a3 connexin knockout mice by using the transgenic expression of a8 connexin in the lens. The generation of these knockout mice will also provide a unique opportunity to identify small biologically relevant molecules that may be transmitted via gap junctional communication to influence the process of cataract formation.
