ID-specific Bmp2, Bmp4, and Bmp7 inactivation results in a decrease in apoptotic cell death. (A-J) E13.5 hindlimbs of Osr1Cre; Bmp2flox/flox; Bmp4flox/flox; Bmp7flox/flox mutants (B, D, F, H, J) and littermate controls (A, C, E, G, I). (A, B) WISH assay for Msx2 mRNA (black arrows indicate downregulation). (C, D) LysoTracker Red and (E, F) cleaved Caspase-3 immunostaining (white arrows, D, and black arrows, F, indicate reduced cell death in ID 2 and 3 of mutants). (G–J) WISH assays for Fgf8 or Rarβ. Note, Fgf8 is appropriately downregulated in the AER overlying the ID region (white arrows, G, H). All views are dorsal with anterior to the left.