APOE and Alzheimer disease: Previous studies have associated the APOE ε4 allele with decreased mao-A mRNA expression in C6 glioblastoma cells (Liu et al., 2012), while risk in a Brazilian cohort of 128 late-onset AD patients was associated with combined MAO-A polymorphism (allele 1; lower transcription efficiency), the short variant of the serotonin transporter promoter, and a positive APOE ε4 status (Nishimura et al., 2005).