Such unusual ossification appears to also occur in response to a congenital vertebral column malformation (VCM) in humans that happens because of a Brachyury gene mutation in the intron 7 [64] and in the highly conserved T-box sequence [71]; these VCMs eventually lead to sacral agenesis (frog-like) syndrome in babies. The gene discussed is TBX1; the disease is Absence of the sacrum.