ID- or AER-specific Bmpr1a inactivation does not affect vascular patterning but results in a decrease of reactive oxygen species. (A–H) Confocal images of E13.75 hindlimbs of Osr1Cre; Bmpr1aflox/null (B, F) or E13.25 forelimbs of Msx2Cre; Bmpr1aflox/null (D, H) mutants and littermate controls (A, C, E, G). (A–D) PECAM whole-mount immunofluorescence to detect vascular patterning. (E–H) Dihydroethidium whole-mount staining to detect reactive oxygen species (ROS). Arrows indicate complete downregulation in ROS, arrowheads indicate a less severe decrease in ROS.