Fig. 9. Id gene expression is decreased in Bmpr double knockout animals. (A) Id1 expression in 10.0 dpc spinal cord in the roof plate and adjacent neural ectoderm of normal animals. There is also a region of ventral expression (arrowhead). (B) In double knockout animals, Id1 expression is greatly reduced in the dorsal neural tube (arrow). The ventral domain of expression (arrowhead) is unaffected. (C) In normal animals, Id2 is expressed diffusely throughout the dorsal half of the neural tube at 10.0 dpc. (D) Expression of Id2 appears unaffected at 10.0 dpc in mutant animals. (E) The roof plate and dorsal neural ectoderm express Id3 in normal animals. (F) In mutant animals, expression of Id3 in the neural ectoderm is diminished (arrow) at 10.0 dpc. (G) Id3 expression at 10.5 dpc in normal embryos. (H) By 10.5 dpc, Id3 expression is abolished in double mutant embryos.