Cell Recognition During Neuronal Development in Insect Embryos

During development, neurons find and interconnect with other neurons in a remarkably precise way. The unfolding of neuronal specificity undoubtedly involves a series of highly specific recognition events between individual neurons. What cellular interactions underlie this specific neuronal recognition? What molecules underlie these specific cellular interactions? To answer these questions, we began several years ago to study cell recognition during neuronal development in the grasshopper embryo. Here we review what we have learned from cellular and immunological studies using the grasshopper embryo. Cell recognition at early stages of neuronal development is mediated largely by specific filopodial contacts, and leads to the stereotyped patterns of selective fasciculation. Our results suggest that such recognition is likely to involve the temporal and spatial expression of many different molecules, and our monoclonal antibody studies reveal cell surface antigens whose distribution correlates with these predictions. We end the paper by reviewing our recent studies on the same cellular interactions in the Drosophila embryo, which leads to a consideration of the future prospects for a molecular genetic solution to this problem using Drosophila.