Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to PMM2-congenital disorder of glycosylation ?
    ### Response:
    PMM2-CDG is caused by mutations in the PMM2 gene. This gene provides instructions for making an enzyme called phosphomannomutase 2 (PMM2). The PMM2 enzyme is involved in a process called glycosylation, which attaches groups of sugar molecules (oligosaccharides) to proteins.
    