Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Greig cephalopolysyndactyly syndrome ?
    ### Response:
    What causes Greig cephalopolysyndactyly syndrome? Mutations in the GLI3 gene cause Greig cephalopolysyndactyly syndrome (GCPS). The GLI3 gene provides instructions for making a protein that controls gene expression, which is a process that regulates whether genes are turned on or off in particular cells.
    