The broad goal of this proposal is to elucidate molecule mechanisms that direct the development of the mammalian forebrain. The characterization of a novel POU-domain gene called Brain-4 (Brn-4) will be used as a paradigm for this broader goal. Members of the POU-domain gene family encode transcription factors; to date, several of these factors have been shown to play critical roles in the development of the anterior pituitary gland and the peripheral nervous system in species ranging from nematodes to man. The spatiotemporal pattern of Brn-4 expression during development suggests a role for Brn-4- in the establishment of morphological boundaries within the embryonic forebrain. In midgestation embryos, hybridization histochemical analyses demonstrate that Brn-4 expression is widely distributed in the central nervous system, including ventricular zones within the forebrain. However, Brn-4 expression is not found in the most rostral aspects of the forebrain in these embryos. The extent of Brn-4 expression observed in the embryonic nervous system becomes restricted to a small subset of structure in late fetal and adult brains. Further hybridization histochemical analyses of Ban-4 expression during mouse ontogeny will clarify the spatial an temporal expression of the Ban-4 gene, its utility as a ventricular zone marker, and its relationship to neurogenesis in the forebrain. To study the molecular basis for the spatiotemporal regulation of Ban-4 expression, the cis- active regulatory element of the gene will be characterized. Once important cis-active sequences are identified, DNA binding assay will be employed to initiate the characterization of transcription factors recognizing these sequences. To investigate the role of the Ban-4 gene product in the context of the entire organism, a mouse pedigree containing a null mutation in the Ban-4 gene will be generated using Embryonic Stem (ES) cell technology. This approach will directly address the function of Ban-4 during mammalian embryogenesis. The characterization of Ban-4 gene e provides a valuable tool with which to address the molecular basis of forebrain development. Analysis of gene regulatory events during the early stages of neurogenesis will help to understand the ontogeny of the central nervous system, and will provide important insights into developmental anomalies affecting nervous system function.