Figure 2. Oculomotor nerve misinnervates lateral rectus muscle, and abducens motor neurons undergo apoptosis following abducens nerve stalling in Chn1^KI/KI mice.

(A–C) Inferior view of EOM innervation in E16.5 Chn1^WT/WT (A; n = 8 orbits), Chn1^KI/KI (B; n = 7 orbits), and Chn1^KO/KO embryos (C; n = 5 orbits). III, oculomotor; IV, trochlear; VI, abducens. LR, lateral rectus muscle; dotted line, abducens; arrow, aberrant branch from division between superior and inferior III; arrowhead, aberrant branch from inferior III branching region; red, smooth muscle actin (EOM); green, Isl^MN-GFP (28). Scale bars: 100 μm. (D) Number of E10.5 abducens motor neurons in Chn1^WT/WT and Chn1^KI/KI embryos. n = 3 embryos; P = 0.231, 2-tailed t test. (E) Number of E13.5 abducens motor neurons for the indicated genotypes. n = 3 embryos each; ***P ≤ 0.001, 1-way ANOVA with Tukey’s test. (F) Representative images of Hb9-GFP abducens motor neurons at E13.5 in indicated genotypes; red, ISL1; green, Hb9-GFP. Scale bar: 50 μm. (G) Whole mount staining of E11.5 Chn1^WT/WT Bax^–/– and Chn1^KI/KI Bax^–/– embryos. Red, neurofilament; green, Hb9-GFP; arrow, abducens nerve stalling. Scale bars: 100 μm. (H) Abducens length measurements in whole mount Chn1^WT/WT Bax^–/– (n = 16 nerves, 8 embryos) and Chn1^KI/KI Bax^–/– embryos (n = 12 nerves, 6 embryos). ***P = 0.001, 2-tailed t test. Graphs represent mean ± SEM.