Ror2 knockout mouse as a model for the developmental pathology of autosomal recessive Robinow syndrome.

Robinow syndrome (RS) is a human dwarfism syndrome characterized by mesomelic limb shortening, vertebral and craniofacial malformations and small external genitals. We have analyzed Ror2(-/-) mice as a model for the developmental pathology of RS. Our results demonstrate that vertebral malformations in Ror2(-/-) mice are due to reductions in the presomitic mesoderm and defects in somitogenesis. Mesomelic limb shortening in Ror2(-/-) mice is a consequence of perturbed chondrocyte differentiation. Moreover, we show that the craniofacial phenotype is caused by a midline outgrowth defect. Ror2 expression in the genital tubercle and its reduced size in Ror2(-/-) mice makes it likely that Ror2 is involved in genital development. In conclusion, our findings suggest that Ror2 is essential at multiple sites during development. The Ror2(-/-) mouse provides a suitable model that may help to explain many of the underlying developmental malformations in individuals with Robinow syndrome.