However, the associations among plasma Aβ42/Aβ40, plasma p-Tau181, and plasma GFAP, as well as their independent and synergistic relationships to Aβ plaque accumulation, tau tangle aggregation, axonal degeneration, hippocampal atrophy, and AD-signature cortical thinning, remain unclear. The gene discussed is GFAP; the disease is Alzheimer disease.