A gene regulatory network in vertebral column driven by Bapx1 and Sox9 . (A) Three layer mechanism of genomic control in the vertebral column by Bapx1 and Sox9. Bapx1 suppresses neuronal genes whereas Sox9 activates them; both activate chondrogenic genes whereas both suppress genes involved in osteogenesis, cartilage degradation and blood vessel development. (B) A large gene regulatory network in the vertebral column of genes that are either activated (green lines) or repressed (red lines) by Sox9 and Bapx1. Each blue dot represents a gene and the common regulated genes are in the center on the network connected to both Sox9 and Bapx1.