Induction of a basement membrane glycoprotein in embryonic kidney: possible role of laminin in morphogenesis.

Abstract

The glycoprotein laminin is found exclusively in the basement membranes of adult tissues, not in the mesenchymal stroma. We studied the appearance and distribution of laminin during the early formation of kidney tubules in mouse embryos and in an in vitro transfilter model system. In immunofluorescence using affinity-purified antibodies, the distribution of laminin showed a clear correlation, both spatially and temporally, to the early stages of tubule formation. In vivo, laminin was first detected in a punctate pattern in areas where the pretubular aggregates form; later, it became confined to the basement membranes of the tubules. In experiments in vitro, the nephrogenic mesenchyme was found to form tubules after 12-24 hr of transfilter contact with the inductor. The first laminin spots were found after 12 hr of culture, 24 hr before overt morphogenesis. As the mesenchymal cells began to aggregate and elongate (at 36 hr), laminin was detected in those cells destined to become epithelial, and at 48 hr it was not found in cells remaining in the stroma. In more mature tubules (at 72 hr), laminin was seen as a sharp band in the basement membranes.

Laminin is induced in astrocytes of adult brain by injury.

“…This is also where fibronectin, the other major matrix glycoprotein, occurs in brain tissue (Schachner et al, 1978;Paetau et al, 1980). Recently, we detected laminin production by rat astrocytes in primary culture (Liesi et al, 1983a) and found that in cultured neuroblastoma cells the ultrastructural localization of laminin (Liesi, 1983) is compatible with a role for this glycoprotein in cell-to-cell and cellto-substratum interactions (Terranova et al, 1980;Ekblom et al, 1980;Liesi, 1983). Brain injury is known to exert a glial reaction that involves a conversion of the protoplasmic astrocytes of the gray matter into reactive astrocytes positive for glial fibrillary acidic protein (GFAP) (Bignami and Dahl, 1974b;Bignami et al, 1980).…”

Laminin is produced by early rat astrocytes in primary culture.

“…Thus the observation that laminin is detected in adult mouse brain only in association with capillary structures (21) may not be in contradiction with our work here. Previously, developmental changes were observed for laminin in differentiation of tubular epithelial cells from the mouse nephrogenic mesenchyme (38).…”

Induction of intermediate mesoderm by retinoic acid receptor signaling from differentiating mouse embryonic stem cells

“…Cryosections of the transplanted kidney were then immunostained for laminin and Pax2 protein expression. Laminin is expressed in the basement membrane of tubule structures in the developing kidney (Ekblom et al, 1980). Pax2 is expressed in collecting duct, metanephric mesenchyme and tubules derived from metanephric mesenchyme (Torres et al, 1995).…”