(A-L) Immunohistochemical analyses in E11.5 CBPf/+;p300f/f;Isl1-Cre- (A-F) and CBPf/+;p300f/f;Isl1-Cre+ (G-L) embryos. Ectopically emigrating motor neurons outside the spinal cord (parenthesis), widened motor exit points (yellow arrows), and erroneous projection of VAChT+ motor axons toward DREZ, roof plate and within DRG (pink arrows) are marked. (M, N) Quantification of Hb9+-motor neurons in the spinal cord (M) and ectopically emigrating Hb9+-motor neurons outside the spinal cord (N) in 12 μm sections at thoracic levels. Asterisk, p<0.001 in the two-tailed t-test. The error bars represent the standard deviation.