Neprilysin Confers Genetic Susceptibility to Alzheimer's Disease in Han Chinese

Alzheimer's disease (AD) is a progressive neurodegenerative disease, with increasing incidence all over the world. Amyloid-beta (A beta) was considered to be the original cause to AD, and many reported pathogenic or risk genes for AD were located in the A beta generation and degradation pathways. Neprilysin (NEP), insulin-degrading enzyme (IDE), and matrix metalloprotease-9 (MMP-9) are the most important A beta-degrading proteases. Accumulating genetic evidence suggested that single nucleotide polymorphisms (SNPs) of these genes confer susceptibility to AD in Caucasian populations. In this study, we screened eight SNPs within these three A beta-degrading protease genes in 1475 individuals of two independent Han Chinese case-control cohorts. SNP rs1816558 of NEP was found to be significantly associated with AD after adjustment for epsilon 4 allele of the apolipoprotein E gene (APOE epsilon 4) and the Bonferroni correction. The remaining variants were not associated with risk of AD in Han Chinese sample set. Further data mining revealed that messenger RNA (mRNA) level of NEP substantially increased during the development of AD and was positively correlated with APP expression. The combined results indicated that NEP confers genetic susceptibility to AD in Han Chinese populations.