IDENTIFICATION OF THE CELLULAR SOURCE OF LAMININ BETA-2 IN ADULT AND DEVELOPING VERTEBRATE RETINAE

The interphotoreceptor matrix (IPM) is a specialized extracellular mat rix that surrounds the inner and outer segments of photoreceptors. Thi s matrix contains molecules that may be important in directing photore ceptor differentiation and survival. For example, one molecule that we have previously identified as a component of the IPM, laminin beta 2 (formerly known as s-laminin), is implicated in the differentiation of rod photoreceptor cells. Developmentally, laminin beta 2 is present b efore rod birth in a position that is consistent with a role in direct ing rod differentiation; it is found, in both the rat and skate, in th e ventricular space that ultimately becomes the IPM. In this study, we identify the source of laminin beta 2 in the adult and developing ret ina. Both immunohistochemistry in the adult skate retina and in situ h ybridizations in the adult rat retina reveal that laminin beta 2 is pr oduced by Muller cells. In addition, in the skate but not the rat reti na, retinal pigment epithelial cells may be an alternative source of l aminin beta 2. During development, however laminin beta 2 is present b efore the birth of Muller glial cells; at this stage of development, l aminin beta 2 RNA is present within the neuroepithelial layer in a pat tern that is consistent with its production by neuroepithelial cells. (C) 1997 Wiley-Liss, Inc.