Fig. 7. Model for the function of SAX-3 in C. elegans embryonic development. During embryonic development most cells reach their final position through a combination of local divisions and directed movements. SAX-3/VAB-1 pathways are required for neuroblast movements that result in the closing of the gastrulation cleft. SAX-3/VAB-1 may also be required to position early AB epidermal precursors that will generate the future epidermal seam cells and ventral epidermal cells. Our results are consistent with SAX-3 functioning with VAB-1 in parallel pathways or perhaps through a receptor complex (SAX-3/VAB-1). At the same time SAX-3 functions independently of VAB-1 for epidermal morphogenesis; for example, during the migration of dorsal epidermal cells.