Structural Switch from Hairpin to Duplex/Antiparallel G-Quadruplex at Single-Nucleotide Polymorphism (SNP) Site of Human Apolipoprotein E (APOE) Gene Coding Region

A gradual dementia, which leads to the loss of memory and intellectual abilities, is the main characteristics of Alzheimer’s disease. Amyloid-β (Aβ) plaques are the main components that accumulate and form clumps in the brains of people suffering from Alzheimer’s disease. Apolipoprotein E (APOE), an amyloid-binding protein is considered as one of the main genetic risk factor of the late-onset Alzheimer’s disease. Different isoforms of APOE gene named APOE2, APOE3, and APOE4 are known to exist, which differ from each other at certain positions involving single-nucleotide polymorphisms (SNPs). Out of these isoforms, APOE4 increases the risk of developing late-onset Alzheimer’s disease, whereas APOE3 is the most common among the general population. APOE4 differs from the common APOE3 by only one nucleotide at position +2985 (T to C), which results in immense alteration in the structure and function of the APOE gene. A combination of gel electrophoresis (polyacrylamide gel electrophoresis, PAGE), circular dic...