Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Treacher Collins syndrome ?
    ### Response:
    What causes Treacher Collins syndrome? Treacher Collins syndrome (TCS) is caused by changes (mutations) in any of several genes: TCOF1 (in over 80% of cases), POLR1C, or POLR1D. In a few cases, the genetic cause of the condition is unknown. These genes appear to play important roles in the early development of bones and other tissues of the face.
    