Other synaptic dysfunction-associated biomarkers for AD include synaptotagmin, a calcium sensor protein, SNAP-25, a component of the soluble N-ethylmaleimide sensitive factor attachment protein receptor complex, GAP-43, a pre-synaptic membrane protein, and synaptophysin, which has exhibited increased levels in the CSF of AD patients [69,76]. Here, GAP43 is linked to Alzheimer disease.