Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to myofibrillar myopathy ?
    ### Response:
    Mutations in several genes can cause myofibrillar myopathy. These genes provide instructions for making proteins that play important roles in muscle fibers. Within muscle fibers, these proteins are involved in the assembly of structures called sarcomeres. Sarcomeres are necessary for muscles to tense (contract).
    