Differential effects of NgCAM and N-cadherin on the development of axons and dendrites by cultured hippocampal neurons

A fundamental step in neuronal development is the acquisition of a polarize d form, with distinct axons and dendrites. Although the ability to develop a polarized form appears to be largely an intrinsic property of neurons, it can he influenced by environmental cues. For example, in cell cultures sub strate and diffusible factors can enhance and orient axonal development. In this study we examine the effects of growth on each of two cell adhesion m olecules (CAMs), NgCAM and N-cadherin, on the development of polarity by cu ltured hippocampal neurons. We find that although the same pattern of devel opment occurs on control substrates and the CAMs, the CAMs greatly accelera te the rate and extent of development of axons-axons form sooner and grow l onger on the CAMs than on the control substrate. In contrast, the CAMs have opposite effects on dendritic development-N-cadherin enhances, but NgCAM r educes dendritic growth corn pa red to control. These results provide furth er evidence that the development of polarity is largely determined by a cel l-autonomous program, but that environmental cues can independently regulat e axonal and dendritic growth.