Fig. 2. Left-right asymmetry specification and limb development are affected in Ftm^-/- embryos. (A-D) Hematoxylin and Eosin stainings at E15.5 on transverse sections. (A) In wild-type mouse embryos lungs branch into four right lobes (R1-R4) and into one left lobe (L1), while in mutant embryos (B) only two symmetric lobes are formed (R1 and L1). (C,D) In wild-type embryos the stomach develops in the left body half (C), while in some Ftm mutant embryos the stomach was positioned on the right (heterotaxia) (D). (E,F) Expression pattern of left-right marker gene. Pitx2 is exclusively expressed in the left lateral plate mesoderm in wild-type embryos at the 2- to 5-somite stages (E). In Ftm^-/- embryos, Pitx2 shows a bilateral expression pattern (F). (G) Bone-cartilage stainings at E18.5 reveal a preaxial polydactyly in mutant limbs, visible by two extra digits in the fore limb and one extra digit in the hind limb. (H,I) At E11.5, expression of Shh appears to be unaffected in Ftm mutant limb buds (H), whereas Ptc1 expression is reduced (I). fl, fore limb; hl, hind limb; st, stomach; wt, wild type.