Fig. 5. Ectopic neurogenesis correlates with an expansion of VIIIth ganglion rudiment form. (A) Mean occurrence of epithelial NeuroD signals (perinuclear rings) by stage and otocyst region for each of the phenotypes examined, obtained by analyses of serial 7 µm thick transverse sections. Between four and eight right otocysts per genotype per stage were analyzed. Data were normalized to account for differences with wild type in average number of sections when this exceeded 5% (normalization factors: E9.5 Tg, 1.08; E9.5 Tbx1^–/–, 1.09; E10 Tbx1^–/–, 1.22; E11 Tbx1^–/–, 1.53; E11 Tbx1^+/–, 1.09). Transgenic data are for Tg^+/+, except at E10 (Tg^+/–). Values are plotted on a log scale, and non-overlapping error bars represent significant differences with P<0.003. At later stages these regions are distinguished as shown in A'. (A') Tracings of E11 wild-type sections at 20 and 32% otocyst (with anterior pole set to zero) showing spatial distributions of NeuroD-positive lateral (red in B) and ventral (cyan in B) cells. a, anterior cardinal vein. Lateral and ventral regions at stages E9.5 and E10 are distinguished by line VL in Fig. S2, http://dev.biologists.org/supplemental/. (B) 3-D reconstructions of E10.5 otocysts and ganglia (red, lateral subdivision; cyan, ventromedial subdivision), obtained by analyses of sections reacted with mAb4D5 (anti-islet1/2). Brackets demarcate regions of delamination in wild type. Otocysts are rendered transparently. ed, endolymphatic duct outgrowth. Scale bar: 100 µm. (C) Representative section of E10.5 Tbx1^–/– posterior otocyst reacted with mAb4D5. Arrows highlight sites of cell delamination into the lateral (red) and ventromedial (cyan) pools. epibr., epibranchial ganglion. Scale bar: 60 µm. (D) Lateral (red arrows) and ventromedial (cyan arrows) mAb4D5-positive nuclei in the wild-type E10.5 ganglion. Scale bar: 10 µm. (E) Section through the posterior pole of the E10.5 Tbx1^–/– otocyst shows delaminating mAb4D5-positive cells.