Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the genetic changes related to isolated Duane retraction syndrome ?
    ### Response:
    In most people with isolated Duane retraction syndrome, the cause of the condition is unknown. However, researchers have identified mutations in one gene, CHN1, that cause the disorder in a small number of families. The CHN1 gene provides instructions for making a protein that is involved in the early development of the nervous system.
    