The slice overlay assay: a versatile tool to study the influence of extracellular signals on neuronal development.

We have developed a technique that allows characterization and identification of extracellular signals that regulate various aspects of neuronal differentiation. In this in vitro assay, dissociated cells isolated from the developing cerebral wall are labeled and cultured over organotypic cortical slices. We have used this slice overlay assay to identify some of the extracellular cues that regulate differentiation and patterning of axons and dendrites in the cerebral cortex. This assay can be easily adapted to identify factors that control other aspects of neuronal development, such as proliferation and survival, and can also be used to evaluate the role of extracellular signals in the development of nonneural tissues.