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.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
1R01EY012142-01
Application #
2602725
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1998-03-01
Project End
2002-02-28
Budget Start
1998-03-01
Budget End
1999-02-28
Support Year
1
Fiscal Year
1998
Total Cost
Indirect Cost
Name
Scripps Research Institute
Department
Type
DUNS #
City
La Jolla
State
CA
Country
United States
Zip Code
92037
Nielsen, Peter A; Beahm, Derek L; Giepmans, Ben N G et al. (2002) Molecular cloning, functional expression, and tissue distribution of a novel human gap junction-forming protein, connexin-31.9. Interaction with zona occludens protein-1. J Biol Chem 277:38272-83
Rong, Pei; Wang, Xin; Niesman, Ingrid et al. (2002) Disruption of Gja8 (alpha8 connexin) in mice leads to microphthalmia associated with retardation of lens growth and lens fiber maturation. Development 129:167-74
Nielsen, P A; Baruch, A; Giepmans, B N et al. (2001) Characterization of the association of connexins and ZO-1 in the lens. Cell Commun Adhes 8:213-7
Baruch, A; Greenbaum, D; Levy, E T et al. (2001) Defining a link between gap junction communication, proteolysis, and cataract formation. J Biol Chem 276:28999-9006
Baldo, G J; Gong, X; Martinez-Wittinghan, F J et al. (2001) Gap junctional coupling in lenses from alpha(8) connexin knockout mice. J Gen Physiol 118:447-56
Gong, X; Agopian, K; Kumar, N M et al. (1999) Genetic factors influence cataract formation in alpha 3 connexin knockout mice. Dev Genet 24:27-32