Fig. 3. Ngn1 expression decreases over time in the prospective utricle. (A) E14.5 utricular macula schematized in the same orientation as the scatterplots in B and E-E''. A cross-section of the macula along the dotted line is represented at the bottom. The macula (region of myosin VIIa staining) is in gray. The active neurogenic region (Ng, region of Ngn1-GFP staining) is white. ut m-lc, non-sensory tissue between the utricular macula and lateral crista; ut m-sac m, non-sensory tissue between the utricular macula and saccular macula. (B) Distribution of GFP⁺ cells (blue crosses, cyan in image) from three E14.5 Ngn1-GFP BAC transgenic utricles, plotted on a normalized scale, defines the region of active neurogenesis. Gray area represents an averaged macular area (myosin VIIa ⁺); the yellow area is non-sensory epithelium between the utricular macula and lateral crista. White arrow marks the lateral extent of the macula. (C) Number of Ngn1 derivatives in the Ngn1-CreER;Z/EG utricle versus time of first tamoxifen feeding for embryos sacrificed at E14.5. Each point is based on four or more ears from two or more litters. (D) Sections through utricular maculae, representing the change in the spatial distribution of Ngn1 derivatives (green) with different tamoxifen regimens. Downturned brackets indicate overlap between Ngn1 derivatives and myosin VIIa ⁺ hair cells. Upturned brackets indicate the region of active neurogenesis. White arrows indicate the lateral extent of the macula. Asterisk shows an Ngn1 derivative in non-sensory tissue between the utricular macula and lateral crista. (E-E''') Spatial distributions of Ngn1 derivatives from E14.5 utricles exposed to different tamoxifen administration regimens, as indicated at the top of each plot. (E) n=4 utricles; (E') n=6 utricles; (E'') n=14 utricles. Ngn1 derivative cell types and regions of the plot are coded as shown in E'''.