Contactin-2 also correlated strongly with another synaptic biomarker, neurogranin (control: r = 0.62, p < 0.05; AD: r = 0.60, p < 0.01), and BACE1, a contactin-2 processing enzyme (control: r = 0.64, p < 0.01; AD: r = 0.46, p < 0.05). Here, BACE1 is linked to Alzheimer disease.