DLG4 and Alzheimer disease: Here, we used two novel pre-commercial Simoa assays developed by Quanterix (Billerica, MA) to measure CSF levels of postsynaptic density protein 95 (PSD-95), a synaptic protein not previously described in the CSF, and SNAP-25, an emerging synaptic biomarker of interest, in subjects with AD, non-AD neurodegenerative diseases, other neurological conditions, and healthy controls.