Detection of a Deletion Polymorphism of the Human α2-Macroglobulin Gene (A2M-2) by a Semi-Automated PCR-Single-Stranded Conformational Polymorphism Method

Several genes such as the genes that code for apolipoprotein E4, amyloid β-precursor protein, and presenilin 1 and 2 have been linked to the development of Alzheimer disease (AD) (1). Recently, a polymorphism of the human α2-macroglobulin gene ( A2M ) was also identified as a risk factor for AD (2). The A2M gene is located on chromosome 12p13.3–p12.3 (3), and its product (α2-macroglobulin) is a serum pan-proteinase inhibitor occurring in many organs and tissues (4). Several studies have suggested that α2-macroglobulin may have protective effect against the deposition of β-amyloids (5)(6) and may stimulate their degradation (7)(8). A 5-nucleotide deletion mutation at the 5′ splice site of “exon II” of the bait region (exon 18; A2M-2 ) may lead to loss of this protection because of its location at the functional domain, and this loss confers increased risk for AD (2). Currently available methods based on DNA sequencing (2)(9), heteroduplex formation in nondenaturing gel (9), and PCR-restriction fragment length polymorphism …