Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to mitochondrial neurogastrointestinal encephalopathy disease ?
    ### Response:
    Mutations in the TYMP gene (previously known as ECGF1) cause MNGIE disease. This gene provides instructions for making an enzyme called thymidine phosphorylase. Thymidine is a molecule known as a nucleoside, which (after a chemical modification) is used as a building block of DNA.
    