Regulates the formation or stabilization of cell-cell contacts at several stages of epithelial morphogenesis. In early embryonic development, required for proper ventral closure of the epidermis. During male tail morphogenesis, regulates precursor cell sorting and allows the formation of distinct sensory rays. Seems to control cell-cell contact formation through 2 parallel pathways, one involving efn-4 and one involving plx-2 and unc-129. Involved in axon guidance. Probably by binding receptor plx-2, regulates fln-1-mediated remodeling of the actin cytoskeleton and thus axon guidance and/or fasciculation of DD/VD neurons. Interacts with plx-2. Belongs to the semaphorin family.