INTERACTIONS BETWEEN GERM-CELLS AND EXTRACELLULAR-MATRIX GLYCOPROTEINS DURING MIGRATION AND GONAD ASSEMBLY IN THE MOUSE EMBRYO

Cells are known to bind to individual extracellular matrix glycoprotei ns in a complex and poorly understood way, Overall strength of adhesio n is thought to be mediated by a combinatorial mechanism, involving ad hesion of a cell to a variety of binding sites on the target glycoprot eins, During migration in embryos, cells must alter their overall adhe siveness to the substrate to allow locomotion, The mechanism by which this is accomplished is not well understood, During early development, the cells destined to form the gametes, the primordial germ cells (PG Cs), migrate from the developing hind gut to the site where the gonad will form, We have used whole-mount immunocytochemistry to study the c hanging distribution of three extracellular matrix glycoproteins, coll agen IV, fibronectin, and laminin, during PGC migration and correlated this with quantitative assays of adhesiveness of PGCs to each of thes e, We show that PGCs change their strength of adhesion to each glycopr otein differentially during these stages, Furthermore, we show that PG Cs interact with a discrete tract of laminin at the end of migration, Closer analysis of the adhesion of PGCs to laminin revealed that PGCs adhere particularly strongly to the E3 domain of laminin, and blocking experiments in vitro suggest that they adhere to this domain using a cell surface proteoglycan.