Yu, T., Graf, M., Renn, J., Schartl, M., Larionova, D., Huysseune, A., Witten, P.E., Winkler, C. (2017) A vertebrate-specific and essential role for osterix in osteogenesis revealed by gene knockout in the teleost medaka. Development (Cambridge, England). 144:265-271.
osterix (osx; sp7) encodes a zinc-finger transcription factor that controls osteoblast differentiation in mammals. Although identified in all vertebrate lineages, its role in non-mammalian bone formation remains elusive. Here, we show that an osx mutation in medaka results in severe bone defects and larval lethality. Pre-osteoblasts fail to differentiate leading to severe intramembranous and perichondral ossification defects. The notochord sheath mineralizes normally, supporting the idea of an osteoblast-independent mechanism for teleost vertebral centra formation. This study establishes a key role for Osx for bone formation in a non-mammalian species, and reveals conserved and non-conserved features in vertebrate bone formation.