DHCR7 and Alzheimer disease: They found four single-nucleotide polymorphisms (SNPs) related to vitamin D insufficiency [described 2.44% of the variance in 25(OH)D], including GC rs2282679 A>C, CYP2R1 rs10741657 T>C, DHCR7 rs12785878 T>C, and CYP24A1 rs6013897 T>A, were associated with an increased risk of developing AD [data from International Genomics of Alzheimer's Project (IGAP)] (Wang et al., 2010; Lambert et al., 2013), and all these four SNPs together can increase the odds of AD by 25%.