The germinal matrices in the developing dentate gyrus are composed of neuronal progenitors at distinct differentiation stages

Abstract

Differentiation of granule cells (GCs) begins from late embryonic stage in the developing dentate gyrus (DG). Migration of the neurogenic stem cells and progenitors in the developing DG makes understanding of the DG morphogenesis difficult. The proliferative area in the developing DG was divided into the three germinal matrices (GMs). However, the stage of the progenitor cells in each GM along the GC differentiation process is not clear. Here, we extensively compared expression of neurogenic transcription factors (TFs) of which sequential expression in the neocortical development and the adult DG neurogenesis was reported. The GC differentiation marked by Prox1 expression takes place from embryonic day 16.5 in the tertiary GM. Although neurogenesis in each GM basically proceeds along the radial axis of the forming GC layer, cells expressing stem cell markers were observed intermingling with NeuroD/Prox1 expressing differentiated cells in the tertiary GM at postnatal day 5, and gradually restricted in the subgranular zone as the development went on. We describe expression pattern of neurogenic TFs during DG development, which suggests conserved sequential expression of TFs in the GC lineage, and spatiotemporal relationships of GC differentiation and DG morphogenesis during embryonic and early postnatal periods.