Delta like 3 (DLL3) is a member of Delta/Serrate/Lag2 (DSL) ligands for Notch receptors and plays a role in Notch signaling. Out of Five DSL ligands, DLL3 is the most structurally divergent DSL ligand. DLL3 is expressed throughout the presomitic mesoderm and is localized to the rostral somatic compartments. Homozygous disruptions of Notch1 and DLL3 result in severe abnormalities in somitogenesis. Mutations in the human DLL3 homolog cause recessive skeletal abnormalities in spondylocostal dysostosis with a consistent pattern of abnormal segmentation.