Function and spatial distribution in developing chick retina of the laminin receptor 6 1 and its isoforms


During the development of the vertebrate nervous system, each neuron has to find its way specifically to a final target where synapse formation occurs. In this process, the growth cones of developing neurons must recognize correct pathways reliably. The complex structure of the embryo makes it necessary for growth cones to respond to a diverse variety of cellular and extracellular substrata which contain the information needed to orient axonal outgrowth. Several classes of molecules have now been ident i fied in the extracellular environment in vivo, which seem to be involved in promoting and guiding axons (reviewed by Dodd and Jessell, 1988; Jessell, 1988). Among these, several components of the extracellular matrix (ECM) seem likely to play important roles (reviewed by Sanes, 1989; Reichardt and Tomaselli, 1991). The best characterized receptors for ECM constituents are integrins, and several members of this family have been shown to be expressed on neurons and to promote neurite outgrowth on ECM-coated substrata in vitro (reviewed by de Curtis, 1991). Laminin (LN) is considered one of the most potent neurite outgrowth-promoting ECM molecules for several neuronal types in culture. Perhaps as many as 27 distinct isoforms of laminin exist as trimeric complexes of three subunits: an A homologue plus a B1 homologue plus a B2 homologue. The rapidly expanding family of identifie d laminin subunits consists at present of 8 polypeptides, three of which are homologues of the A subunit; two or three of which are B1 subunit homologues; and two of which are B2 chain homologues (cf. Sanes et al., 1990; Kallunki et al., 1992; O’Rear, 1992). While a few preliminary studies have been done characterizing neuronal interactions with partially purified preparations of other laminin isoforms, the most definitive studies to date have been done only with the first identified laminin isoform, which contains the A, B1 and B2 subunits (reviewed in de Curtis, 1991). In particular, studies in vitro have shown that embryonic day 6 (E6) neural retinal cells attach and spread on laminin, extending long neurites within 24 hours (Cohen et al., 1986; Hall et al., 1987). The effect of laminin on neurite outgrowth from E6 neural retinal cells and retinal ganglion cells can be completely abolished by the presence of monoclonal antibodies to the integrin β1 subunit (Cohen et al., 1986; Hall et al., 1987), implicating one or more β1class integrin receptors in interactions of these cells with 377 Development 118, 377-388 (1993) Printed in Great Britain © The Company of Biologists Limited 1993

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@inproceedings{Curtis1996FunctionAS, title={Function and spatial distribution in developing chick retina of the laminin receptor 6 1 and its isoforms}, author={Ivan de Curtis and Louis French Reichardt}, year={1996} }