- The apolipoprotein E epsilon 4 allele does not influence the clinical expression of the amyloid precursor protein gene codon 693 or 692 mutations. Haan, J., Van Broeckhoven, C., van Duijn, C.M., Voorhoeve, E., van Harskamp, F., van Swieten, J.C., Maat-Schieman, M.L., Roos, R.A., Bakker, E. Ann. Neurol. (1994)