Acts as a ligand for Notch receptors and is involved in primary neurogenesis. Can activate Notch receptors, thereby playing a key role in lateral inhibition, a process that prevents the immediate neighbors of each nascent neural cell from simultaneously embarking on neural differentiation. Expressed in the epiblast (the future neurectoderm) and in neuroblasts. Expressed in overlapping regions with deltaA (dla) and deltaD (dld), but differs in the neural plate: it is apparently confined to the scattered cells within those patches that differentiate as neurons, while dla and dld are expressed in patches of contiguous cells. Ubiquitinated by mib, leading to its endocytosis and subsequent degradation.