DLL1 also known as Delta is a human homolog of the Notch Delta ligand and is a member of the delta/serrate/jagged family. DLL1 plays a crucial role in cell signaling pathways essential for proper development and differentiation of various cell types. DLL1 interacts with Notch receptors to regulate cell fate decisions, influencing the balance between cell proliferation and differentiation. Such interaction is particularly important in hematopoiesis, where DLL1 promotes the emergence of T cell and natural killer cell characteristics while inhibiting progenitor cell differentiation into the B cell lineage. DLL1 functions as a membrane protein expressed in key tissues such as heart, pancreas, brain, and muscle during critical developmental stages like gastrulation and early organogenesis, as well as in adult heart and lung tissues.