This demonstrated that CSF levels of PSD-95 on average were significantly higher in subjects with AD (452±176 pg/ml; Fig. 2A) compared to subjects with NeuroDegen diseases (316±271 pg/ml; p<0.001), NeuroCtrls (308±268 pg/ml; p<0.0005), and HC (213±70 pg/ml; p<0.0001). The gene discussed is DLG4; the disease is Alzheimer disease.