Syndrome de Treacher Collins is a genetic disorder caused by a mutation in the TCOFI gene. This gene helps regulate the Treacle protein, which is thought to help the bones and facial tissues develop properly. Researchers are still unsure of the complete role of the protein, but they do know it is very important for facial development both in the womb and after birth. The mutation causes a decline in the amount of available Treacle protein, which may change the actual cells that form facial features.