Panel A, lateral view of Prdm16−/− (−/−) and wild-type (+/+) fetal heads stained with alcian blue and alizarin red and cleared. Reduced chondrogenesis is evident in the nasal cartilage (nc), parietal bone (p), temporal bone (tem), and Meckel’s cartilage (mc) of Prdm16−/− fetuses. Significant reduction in the length of Meckel’s cartilage is also apparent. Panel B, frontal view of the same specimens in Panel A illustrating the lack of fusion of Meckel’s cartilage in Prdm16−/− fetuses at the anterior-most aspect (red arrow) and an overall reduced intensity of alcian blue staining. Scale bars, 1 mm.