Diagram of the vesicle trafficking model of WT and Atm KO synapses. Our model proposes that in synapses, ATM protein localizes predominately in presynaptic terminals, while ATR localizes on both side of synapse. ATM binds exclusively to VGLUT1+ vesicles, while ATR localizes only to VGAT+ vesicles. Compared with WT, Atm KO neurons show decreased E/I balance, impaired clathrin-mediated synaptic vesicle endocytosis, increased ATR protein levels, and larger vesicle size.