LAUSR

Neuronal subtype specification in the vertebrate neural tube is one of the best-studied examples of embryonic pattern formation. Distinct neuronal subtypes are generated in a precise spatial order from progenitor cells according to their location along the anterior-posterior and dorsal-ventral axes. Underpinning this organization is a complex network of extrinsic and intrinsic factors. Secreted proteins, including Sonic Hedgehog (Shh) and BMP familymembers act in a graded fashion to organize the pattern of neurogenesis. This is a dynamic process in which increasing concentrations and durations of exposure to the signals generate neurons with distinct. Underpinning this process is a transcription network controlled by the patterning signals that plays an essential role in determining the graded response of cells. Thus the accurate patterning of the neural tube and the specification of neuronal subtypes at appropriate positions within the neural tube relies on the continuous processing and constant refinement of the cellular response to graded signaling inputs.