Finally, p53 appears to be causally related to the defects seen in the Treacher Collins syndrome (TCS), a congenital disorder of craniofacial development arising from mutations of TCOF1, which encodes the nucleolar phosphoprotein Treacle and whose haploinsufficiency perturbs mature ribosome biogenesis to trigger p53 activation (Jones et al., 2008). The gene discussed is TCOF1; the disease is Treacher-Collins syndrome.