Fig. 6. Overexpression of Wnt5b delays chondrocyte differentiation. (A) Consecutive sections of the humerus at 15.5 dpc. Wnt5b was expressed in the prehypertrophic chondrocytes where Ihh was expressed. Its expression also extended into the hypertrophic region. Wnt5b expressing chondrocytes were more differentiated than Wnt5a-expressing chondrocytes. (B) Skeletal preparation of 17.5 dpc embryos. The Col2a1-Wnt5b embryo had an open skull (arrow), significantly shortened long bones and reduced ossification in the limb, and smaller rib cages. Forelimbs are shown separately. (C) Expression of markers for chondrocyte differentiation at 15.5 dpc. The expression of Wnt5a, Ihh and Col10a1 (ColX in figure) was not detected in the chondrocytes in the transgenic embryos. Expression in the digits was not affected (arrow). (D) BrdU labeled cells on sections of the distal humerus of 17.5 dpc embryos are shown. More chondrocytes were labeled by BrdU in the Col2a1-Wnt5b embryos, especially in Zone I. The columnar chondrocyte structure was disrupted in the Col2a1-Wnt5b embryo.