Fasciclin I and II have distinct roles in the development of grasshopper pioneer neurons.

We have used a new technique, micro-CALI (chromophore-assisted laser inactivation), to investigate the function of the neural cell adhesion molecules fasciclin I and II in the development of the grasshopper Ti1 neurons. Micro-CALI of fasciclin I results in defasciculation of the Ti1 axons similar to that achieved using large scale CALI (Jay and Keshishian, 1990). The initial point of axon separation corresponds to the site of laser irradiation, and defasciculation always continues distal to this point. Micro-CALI of fasciclin II prevents the initiation of Ti1 axon outgrowth but has no effect on fasciculation. This effect is restricted to a 3 hr interval between cytokinesis and growth cone emergence.