Inhibits primary neurogenesis. May be required to divert neurons along a specific differentiation pathway. Plays a role in the formation of somite boundaries during segmentation of the paraxial mesoderm (By similarity). Can bind and activate Notch-1 or another Notch receptor. The DSL domain is required for binding to the Notch receptor. Ubiquitinated by MIB (MIB1 or MIB2), leading to its endocytosis and subsequent degradation.