The loss of DPP6 function is involved in the dysfunction of neuronal excitability (hyperexcitability) [100], aging DPP6-KO mice have increased numbers of novel, abnormal presynaptic structures associated with several markers of AD [101], and the downregulation of DPP6 was associated with a reduced dendritic spine density, which is a phenotype observed in AD brains [102]. Here, DPP6 is linked to Alzheimer disease.