Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Juvenile primary lateral sclerosis ?
    ### Response:
    What causes juvenile primary lateral sclerosis? Juvenile primary lateral sclerosis is caused by mutations in the ALS2 gene. The ALS2 gene provides instructions for making a protein called alsin. Alsin is abundant in motor neurons, but its function is not fully understood.
    