Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Holt-Oram syndrome ?
    ### Response:
    What causes Holt-Oram syndrome? Holt-Oram syndrome is caused by changes (mutations) in the TBX5 gene. This gene gives the body instructions for making a protein involved in the development of the heart and upper limbs before birth. In particular, this gene seems important for dividing the developing heart into four chambers, and in regulating the development of bones in the arms and hands.
    