Linkage analysis for plasma amyloid beta levels in persons with hypertension implicates A beta-40 levels to presenilin 2

Plasma concentrations of A beta 40 and A beta 42 rise with age and are increased in people with mutations that cause early-onset Alzheimer's disease (AD). Amyloid beta (A beta) plasma levels were successfully used as an (endo)phenotype for gene discovery using a linkage approach in families with dominant forms of disease. Here, we searched for loci involved in A beta plasma levels in a series of non-demented patients with hypertension in the Erasmus Rucphen Family study. A beta 40 and A beta 42 levels were determined in 125 subjects with severe hypertension. All patients were genotyped with a 6,000 single nucleotide polymorphisms (SNPs) illumina array designed for linkage analysis. We conducted linkage analysis of plasma A beta levels. None of the linkage analyses yielded genome-wide significant logarithm of odds (LOD) score over 3.3, but there was suggestive evidence for linkage (LOD > 1.9) for two regions: 1q41 (LOD = 2.07) and 11q14.3 (LOD = 2.97), both for A beta 40. These regions were followed up with association analysis in the study subjects and in 320 subjects from a population-based cohort. For the A beta 40 region on chromosome 1, association of several SNPs was observed at the presenilin 2 gene (PSEN2) (p = 2.58 x 10(-4) for rs6703170). On chromosome 11q14-21, we found some association (p = 3.1 x 10(-3) for rs2514299). This linkage study of plasma concentrations of A beta 40 and A beta 42 yielded two suggestive regions, of which one points toward a known locus for familial AD.