Specification and maintenance of the spinal cord stem zone

Abstract
Epiblast cells adjacent to the regressing primitive streak behave as a stem zone that progressively generates the entire spinal cord and also contributes to paraxial mesoderm. Despite this fundamental task, this cell population is poorly characterised, and the tissue interactions and signalling pathways that specify this unique region are unknown. Fibroblast growth factor (FGF) is implicated but it is unclear whether it is sufficient and/or directly required for stem zone specification. It is also not understood how establishment of the stem zone relates to the acquisition of spinal cord identity as indicated by expression of caudal Hox genes.