Lack of association between cathepsin D genetic polymorphism and Alzheimer disease in a Spanish sample

Cathepsin D (catD) is an intracellular aspartyl protease that exhibits beta and gamma secretase-like activity to cleave amyloid precursor protein into beta amyloid peptide. The T-allele of a biallelic (alleles C and T) polymorphism in the exon 2 of the catD gene has been found to be associated with increased risk of Alzheimer disease (AD) in two independent German populations. Other groups have been unable to replicate this association in Caucasian American and Northern Ireland populations. Moreover, a small and no significant tendency for the T-allele to be protective for AD has been demonstrated in Caribbean Hispanics. A case control study utilizing a clinically well-defined group of 311 sporadic AD patients and 346 control subjects was performed to test this association in an ethnically homogeneous population from Spain. We did not observe any association between the T-allele of the catD gene and the disease. Furthermore, catD was not predictive of AD in an interactive fashion when considering apolipoprotein E, age, or gender.