Fig. 2. Skeletal abnormalities of Tbx15 mutants. Alcian Blue and Alizarin Red staining of newborn and E13.5 wild-type and Tbx15 mutants. (A) Newborn Tbx15 mutants have a foramen in the blade of the scapula and the humerus is shorter than in wild type. (B,C) Alcian Blue staining of E13.5 wild-type (B) and Tbx15 mutant (C) shoulder girdle. At this stage the phenotype is already present. (D) Abnormalities of the caudal posterior aspect of vertebrae in newborn Tbx15 mutants. Arrow indicates ectopic cartilage in the atlas of Tbx15 mutant; arrowhead indicates the place were the dens of the axis is missing. (E,F) Cranial base of a newborn wild-type (E) and Tbx15^–/– (F) skull. The Tbx15 mutant skull is shorter and narrower than the wild type, and the basioccipital bone (B) is narrow when compared with wild type; also the inner ear (I) has an abnormal medial and caudal position.