The major transcript of the FE65 gene is a neuron-specific mRNA that encodes a nuclear protein whose aminoterminal domain strongly activates the transcription of a reporter gene when fused to a heterologous DNA-binding domain. FE65 gene expression is regulated during neuronal differentiation of the NTERA-2 cell line, and it is temporally and spatially restricted during mouse embryo development. It is first detected around day 10 of gestation in the basal plate of the neural tube, and then, at the subsequent stages of development and in the newborn animals, it is found solely in neural structures. Its expression is most abundant in the neural crest derivatives (e.g. spinal and encephalic ganglia), ganglionic structures of sense organs (ganglionic layer of the retina and olfactory epithelium), as well as the ganglionic structures of the autonomic nervous system. Thus FE65 gene expression can be considered a marker of the development of embryo ganglionic derivatives.