In vitro assay to test differential substrate affinities of growing axons and migratory cells

Abstract

An in vitro assay is presented in which different soluble substrates are arranged in narrow alternating stripes which forces growing axons and migratory cells to choose between them. The usefulness of this assay is exemplified by offering goldfish retinal axons and glial cells of the optic nerve a variety of substrates in stripes. Given a choice between substrates of unequal growth supporting activities axons and migratory cells grow in stripes, thus expressing their preference for one of the substrates. Growth in stripes was observed 1. when a substrate with growth promoting properties was next to one which did not possess these properties, 2. when the growth promoting activity of a substrate applied to both stripes was in one stripe blocked by an antibody, 3. when two different growth promoting substrates were offered. A choice assay similar in its design has been described earlier (Walter et al. 1987a, b), in which growing retinal axons were exposed to cell surface membranes of two different regions of their target (Walter et al. 1987a, b; Vielmetter and Stuermer 1989a). In contrast to the membrane assay in the assay of the present study soluble proteins are bound to glass supports in narrow alternating stripes. To demonstrate the ability of axons and cells to express a preference when being exposed to "striped" substrates we used goldfish retinal axons and migratory goldfish glial cells (Bastmeyer et al. 1989) and a variety of proteins as substrates. Some of these results have been published in abstract form (Vielmetter et al. 1986).