- Variation in the DCP1 gene, encoding the angiotensin converting enzyme ACE, is not associated with increased susceptibility to Alzheimer's disease. Carbonell, J., Allen, R., Kalsi, G., McQuillin, A., Livingston, G., Katona, C., Walker, Z., Katz, A., Rands, G., Stevens, T., Crossan, I., Curtis, D., Gurling, H. Psychiatr. Genet. (2003)