Expression and regulation of alpha1beta1 integrin in Schwann cells.

The interaction of cells with the extracellular matrix plays a critical role in morphogenesis and cell differentiation. To define how Schwann cells might interact with the extracellular matrix, we chose to study the expression of the laminin/collagen receptor alpha1beta1 integrin during nerve development in the rat from embryonic day 14 to maturity. We found that this integrin is expressed predominantly on mature non-myelin-forming cells and only at very low levels on myelin-forming cells. Significant levels of this integrin were not detected on Schwann cell precursors or embryonic Schwann cells in vivo. Experiments using transected and crushed sciatic nerve showed that alpha1beta1 integrin expression is regulated at least in part by axonal contact. Furthermore, Schwann cell culture experiments showed that alpha1beta1 integrin levels are strongly upregulated by transforming growth factor-beta(s) and phorbol esters.