DeltaD is one of the 4 members of the zebrafish Delta family of Notch ligands, important in the control of cell differentiation in many tissues.
DeltaD acts as a ligand for Notch receptors and is involved in primary neurogenesis and somitogenesis. It 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. It is required in somite segmentation to keep the oscillations of neighboring presomitic mesoderm cells synchronized.