CONICET | Buscador de Institutos y Recursos Humanos

Considerable progress has been made in understanding the mechanisms that control the production of specialized neuronal types in the developing spinal cord. We have recently identified the generation of neurons in the mouse spinal cord during advanced embryonic stages, at the ?gliogenic phase? previously considered non-neurogenic. These late neurogenic events exclusively give rise to cerebroSpinal Fluid-contacting Neurons (CSF cN), an anatomically discrete cell type of the ependymal area of the spinal cord. The genetic mechanisms that allow the differentiation of this class of neurons at gliogenic stages are unknown. In this work, we identified that the transcription factors Ascl1, Gata3 and Gata2 are sequentially expressed in the mouse CSF-cN and control their specification. Through expression analysis and mouse genetics, we found that Gata3 and Gata2 are expressed in newborn CSF-cN, where they control the acquisition of this precise neuronal identity. Loss of function experiments showed that Gata3 andGata2 play distinct roles in different CSF-cN subsets. Meanwhile, the proneural protein Ascl1 is restricted to the late ventral progenitors that give rise to CSF-cN and initiates their differentiation. By temporally dissecting Ascl1 activity, we found that this transcription factor is an essential component for late CSF-cN neurogenesis, acting at the time of their specification. Finally, fate mapping experiments in the absence of Ascl1 demonstrate that Ascl1 confersneurogenic potential to late ventral progenitors, which otherwise become ependymal cells. We conclude that the sequential action of Ascl1-Gata3/2 directs late neuronal differentiation in the mouse spinal cord to produce this enigmatic class of spinal cord neurons.