AbstractPhysical interaction between the transmembrane proteins Delta and Notch allows only a subset of neural precursors to become neurons, as well as regulating other aspects of neural development. To examine the localization of Delta protein during neural development, we generated an antibody specific to zebrafish DeltaA (Dla). Here, we describe for the first time the subcellular localization of Dla protein in distinct puncta at cell cortex and/or membrane, supporting the function of Dla in direct cell–cell communication. In situ RNA hybridization and immunohistochemistry revealed dynamic, coordinated expression patterns of dla mRNA and Dla protein in the developing and adult zebrafish nervous system. Dla expression is mostly excluded from differentiated neurons and is maintained in putative precursor cells at least until larval stages. In the adult brain, dla mRNA and Dla protein are expressed in proliferative zones normally associated with stem cells. Developmental Dynamics 238:3226–3336, 2009. © 2009 Wiley‐Liss, Inc.