The invention provides nucleic acids encoding Delta3 proteins. Also provided are derivatives of Delta3 nucleic acids, polypeptides encoded thereby, and antibodies. Delta3 therapeutics, which are either antagonists or agonists of a Delta3 bioactivity and which are capable of modulating the growth and/or differentiation of a cell, e.g., endothelial cell, are also provided herein. Furthermore, methods for treating or preventing diseases associated with an aberrant Delta3 activity and/or associated with abnormal cellular growth and/or differentiation, e.g., neurological disease or vascular disease, such as Agenesis of the Corpus Callosum with Peripheral Neuropathy (ACCPN), as well as diagnostic methods for detecting these diseases are disclosed.
