Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to primary myelofibrosis ?
    ### Response:
    Mutations in the JAK2, MPL, CALR, and TET2 genes are associated with most cases of primary myelofibrosis. The JAK2 and MPL genes provide instructions for making proteins that promote the growth and division (proliferation) of blood cells. The CALR gene provides instructions for making a protein with multiple functions, including ensuring the proper folding of newly formed proteins and maintaining the correct levels of stored calcium in cells.
    