Conditional Inactivation of Connexin43 in the Non-Pigmented Cells of the Ciliary Body Reduces Gap Junctions and Intraocular Pressure
Monica Calera 1,
Zhao Wang 2,
Roberto Sanchez-Olea 1,
David Paul 3,
Mortimer M. Civan 4,
and
Daniel Goodenough 5*
1 Instituto de Fisica, Universidad Autonoma de San Luis Potosi, San Luis Potosi, Mexico
2 Physiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States
3 Neurobiology, Harvard Medical School, Boston, Massachusetts, United States
4 Department of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania, United States
5 Cell Biology, Harvard Medical School, Boston, Massachusetts, United States
* To whom correspondence should be addressed. E-mail: daniel_goodenough{at}hms.harvard.edu.
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Abstract |
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PURPOSE. Conditional inactivation of Cx43 in the pigmented epithelium of the mouse eye results in a reduction in aqueous humor production and complete loss of the vitreous chamber. It was proposed that gap junctions between pigmented and non-pigmented epithelia of the ciliary body are critical for the production of the aqueous humor. To form such junctions, Cx43 in the pigmented epithelium must interact with connexin(s) present in the adjacent cells of the non-pigmented epithelium. Here, we tested the importance of Cx43 expression in the nonpigmented epithelium for the establishment of gap junctions and the regulation of intraocular pressure.
METHODS. To inactivate Cx43 in the non-pigmented epithelium of the mouse eye we crossed a mouse line with a floxed Cx43 locus (Cx43flox/flox) and a transgenic mouse line expressing cre recombinase under the control of the Pax6
promoter. General eye structure was evaluated by light microscopy, gap-junctions were analyzed by electron microscopy and intraocular pressure was directly assessed with micropipettes.
RESULTS. In Pax6-cre/Cx43flox/flox mice, Cx43 was partially inactivated in the nonpigmented epithelium of the ciliary body and iris. Animals developed dilatations between the pigmented and non-pigmented epithelia and displayed a significant reduction in intraocular pressure. However, gap-junctions between the ciliary epithelial layers were decreased but not eliminated.
CONCLUSIONS. Cx43 expression in the non-pigmented epithelium of the ciliary body contributes to the formation of gap-junctions with the cells of the pigmented epithelium. These gap-junctions play a critical role in maintaining a physical integrity of the ciliary body epithelium. While the partial loss of Cx43 from the non-pigmented epithelium was correlated with a measurable drop in intraocular pressure, possible changes in Cx43 in the aqueous outflow pathway may provide an additional contribution to the observed phenotype.
Key Words:
gap junctions, ciliary epithelium, connexins, knockout animals, immunocytochemistry, intraocular pressure
