Fig. 4. Limb abnormalities in Tbx3^tm1Pa homozygous mutant (–/–) mice. (A-C) Limb morphology of 12.5 dpc embryos. The hindlimb of Tbx3 mutant mice (B,C) is more severely affected than the forelimb, although the phenotype is variable between mice and between contralateral sides of the same mouse. (D) Histology of the forelimb and hindlimb (inset) of a homozygous mutant embryo showing abnormal development of the hand plate and severe truncation of the hindlimb. (E,F) Left and right sides of a homozygous mutant embryo recovered dead near term. (G) Skeletal preparation of limbs from embryo in E,F. The forelimbs exhibit variable abnormalities of the posterior elements, including the ulna and digits, whereas the hindlimb shows severe truncations with a posterior deflection of the zeugopod and no development of the autopod. (H) Right hindlimb of a late term homozygous mutant fetus at higher magnification, showing the single digit attached to the single zeugopod element. (I) Skeletal preparation of the limbs from a normal age-matched control, at the same magnification as G. AER, apical ectodermal ridge.