- No evidence for genetic association or linkage of the cathepsin D (CTSD) exon 2 polymorphism and Alzheimer disease. Bertram, L., Guénette, S., Jones, J., Keeney, D., Mullin, K., Crystal, A., Basu, S., Yhu, S., Deng, A., Rebeck, G.W., Hyman, B.T., Go, R., McInnis, M., Blacker, D., Tanzi, R. Ann. Neurol. (2001)