Fig. 1. Ngn2 is expressed in the different progenitor populations of the developing dentate gyrus. (A,B) Sections through the hippocampus of E18.5 wild-type embryos showing the expression of Ngn2 transcripts by in situ hybridization (A) and of Ngn2 protein by immunohistochemistry (B). The different progenitor populations of the developing DG (1ry, primary matrix; 2ry, secondary matrix; 3ry, tertiary matrix) are outlined. (C) Histograms of the number of Ngn2-expressing cells in the different progenitor populations of the DG. (D-G) Sections through the hippocampus of E18.5 brains double-labelled for Ngn2 and BrdU following a 30 minute pulse (D-D''), Prox1 (E-E''), Neurod1 (F-F'') and Ki67 (G). Pictures were taken at the level of the primary matrix (D,E,F), secondary matrix (D',E',F') or tertiary matrix (D'',E'',F'',G). Arrows indicate double-labelled cells, while arrowheads indicate Ngn2-expressing cells only. (D''') Histogram representing the percentage of Ngn2-expressing cells having incorporated BrdU (blue bars) and the percentage of BrdU-labelled cells expressing Ngn2 (red bars). (E''') Histogram representing the percentage of Ngn2⁺ cells expressing Prox1 at a low level (blue bars) and the percentage of Prox1^low cells expressing Ngn2 (red bars). Ngn2 is expressed only in progenitors expressing Prox1 at a low level and not in post-mitotic neurons expressing Neurod1 and Prox1 at a high level. Scale bars: 20 µm.