Abstract
Abstract: :
Purpose: Two aquaporins are expressed in the mammalian lens, AQP0 and AQP1. AQP0 is expressed in the lens fiber cells; AQP1 is expressed in lens anterior and differentiating epithelial cells. AQP1 expression is shut down and protein is degraded during fiber cell differentiation. At this same point in differentiation, AQP0 expression is turned on. The aim of this investigation was to determine the expression of aquaporin proteins during the successive developmental stages in mouse lens. Methods: Mouse embryos (E9.0, E10.0; E = Embryonic day), heads (E11.0–E15.0), eyes (E16.0–20.0), lenses of pups (P1–P20; P= Post–natal day) and lenses of adult mice were dissected and fixed in fresh 4% paraformaldehyde. Immunofluorescent labeling of cryosections (8 µm thick)of these samples was carried out using anti–AQP1 and anti–AQP0 antibodies and FITC–conjugated secondary antibodies. The sections were mounted in Vectashield mounting medium containing the nuclear stain DAPI and viewed in 0.25 µm vertical increments using a Zeiss Axiovert 200M epifluorescent microscope equipped with FITC and DAPI specific filters. Images were captured using AxioCam MRm digital camera, then deconvoluted and analyzed using Axio Vision 4.01 software. Results: Expression of AQP1 was first detected in lens epithelial cells at stage E9.0 and continued through the adult stage. AQP1 was essentially undetectable in primary or secondary differentiating fiber cells or mature fiber cells. We first detected AQP0 protein at E11.5 in the differentiating primary fiber cells; its synthesis continued through the adult stage in the secondary fiber cells, which differentiate from the equatorial epithelial cells. Conclusions: Expression of AQP0 in primary fiber cells during early embryonic stages ensures its presence in the central fiber cells of mature lenses. The complete separation of AQP0 and AQP1 expression suggests different roles in the different cell types. However, both are known to be transmembrane water channels, so some other role must be found to account for the differential pattern of expression.
Keywords: gene/expression • gap junctions/coupling • cataract