Recombinant mouse Dner and Notch1 can be co-immunoprecipitated when exogenously expressed in human embryonic kidney cell line HEK293. Dner has ten extracellular EGF repeats, highly homologous to EGF repeats of Notch and Delta proteins. The first two repeats at the N-terminus of Dner are critical for binding to Notch1. In mouse cerebellum, Dner is strongly expressed on dendrites and cell bodies of Purkinje cells, while Notch1 is expressed in Bergman glia that are in contact with Purkinje cells and extends massive radial fibers that traverse the cerebellar cortex along with Purkinje cell dendrites. When a primary culture of cerebellar glia is incubated with soluble mouse Dner, the extension of cellular processes in Notch1 positive cells, thought to be derived from the developing Bergmann glia, is increased, and this effect of is dependent on gamma-secretase activity as well as the presence of Dtx.