Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to dopa-responsive dystonia ?
    ### Response:
    Mutations in the GCH1 gene are the most common cause of dopa-responsive dystonia. Less often, mutations in the TH or SPR gene cause this condition.  The GCH1 gene provides instructions for making an enzyme called GTP cyclohydrolase. This enzyme is involved in the first of three steps in the production of a molecule called tetrahydrobiopterin (BH4).
    