Genome-wide association study identifies multiple novel loci associated with disease progression in subjects with mild cognitive impairment

Alzheimer's disease (AD) is the leading cause of dementia among the elderly population; however, knowledge about genetic risk factors involved in disease progression is limited. We conducted a genome-wide association study (GWAS) using clinical decline as measured by changes in the Clinical Dementia Rating-sum of boxes as a quantitative trait to test for single-nucleotide polymorphisms (SNPs) that were associated with the rate of progression in 822 Caucasian subjects of amnestic mild cognitive impairment (MCI). There was no significant association with disease progress for any of the recently identified disease susceptibility variants in CLU , CR1 , PICALM , BIN1 , EPHA1 , MS4A6A , MS4A4E or CD33 following multiple testing correction. We did, however, identify multiple novel loci that reached genome-wide significance at the 0.01 level. These top variants (rs7840202 at chr8 in UBR5 : P =4.27 × 10 −14 ; rs11637611 with a cluster of SNPs at chr15q23 close to the Tay–Sachs disease locus: P =1.07 × 10 −15 ; and rs12752888 at chr1: P =3.08 × 10 −11 ) were also associated with a significant decline in cognition as well as the conversion of subjects with MCI to a diagnosis of AD. Taken together, these variants define approximately 16.6% of the MCI sub-population with a faster rate of decline independent of the other known disease risk factors. In addition to providing new insights into protein pathways that may be involved with the progress to AD in MCI subjects, these variants if further validated may enable the identification of a more homogeneous population of subjects at an earlier stage of disease for testing novel hypotheses and/or therapies in the clinical setting.