Twist1 mediates repression of chondrogenesis by β-catenin to promote cranial bone progenitor specification.

The bones of the mammalian skull vault form through intramembranous ossification. Skull bones ossify directly, in a process regulated by β-catenin, instead of passing through a cartilage intermediate. We tested whether β-catenin is necessary for fate selection of intramembranous bone progenitors in the skull.