Fig. 4. Expression of bHLH factors shows loss of Math1 expression, and a dorsal shift of Ngn2 and Mash1 expression in Bmpr double knockout animals. (A) Math1 is expressed in the ventricular zone of the dorsal neural tube (arrow) in normal animals at 10.5 dpc. (B) Math1 expression is lost in Bmpr double knockout animals. (C) Ngn2 expression in a subset of neural progenitors (arrow) is found ventral to Math1 expression in normal animals and (D) is intact but dorsally shifted (arrowhead) in Bmpr double knockout animals at 11.0 dpc. (E) In normal animals, Mash1 expression marks the remainder of the dorsal ventricular zone (arrow) at 11.0 dpc. (F) In mutant animals, Mash1 expression is dorsally shifted (arrowhead).