LAMININ ALPHA-5-CHAIN IS EXPRESSED EARLY AND WIDELY DURING THE DEVELOPMENT OF THE ANTERIOR SEGMENT OF RAT EYE

The distribution of a novel laminin alpha 5-chain in the basement memb ranes of the anterior segment of rat eye was studied. Frozen sections of embryonic day (E)16-17, post-natal day (P)2, 5, 10, 15 and 30 and a dult rat eyes were immunostained for laminin chains alpha 2, alpha 5, beta 1, beta 2 and gamma 1 and for laminin-5, as well as for EHS-lamin in, to visualize all basement membranes. Laminin alpha 5-, beta 1- and gamma 1-chain immunoreactivities were found in the basement membranes of the inner and outer layers of optic cup, lens epithelium, further corneal epithelium and skin of the eyelids in E16-17 rat eyes. In P2 a nd older rat eyes, laminin alpha 5-, beta 1- and gamma 1-chains were a ll seen in the basement membranes of the corneal and conjunctival epit helium, Descemet's membrane, lens epithelium, ciliary processes, blood vessels and skin of the eyelids. There was a change in the expression pattern of laminin alpha 5, beta 1- and gamma 1-chains in Descemet's membrane from the endothelial side of the membrane (P2-P15 eyes) to bo th sides of the membrane after P30. Immunoreactivity for laminin-5 was weak in the basement membrane of E16-17 epidermis, but strong in the basement membrane of corneal, conjunctival and eyelid epithelium in P2 and older rat eyes. Laminin alpha 2- and beta 2-chains were seen in c onjunctival and uveal blood vessels in P15 and older rat eyes. The lam inin beta 2-chain emerged into the basement membrane of conjunctival e pithelium in P30 and older rat eyes, suggesting a role for the laminin beta 2-chain in the maturation of conjunctiva. The results suggest th at laminin alpha 5-chain, possibly in laminin-10 (alpha 5 beta 1 gamma 1), is early and widely expressed in the basement membranes of develo ping and adult rat eye and, further, that laminin alpha 5-chain is a m ajor laminin a-chain, partly in coexpression with the alpha 3-chain of laminin-5 in the basement membranes of the anterior segment of the ey e in developing and adult rats. (C) 1998 Chapman & Hall.