SYNDIG1 (synapse differentiation inducing 1) is a type II transmembrane protein that plays a critical role in excitatory synapse development and AMPA receptor regulation at nascent synapses 1. The protein directly binds to AMPA receptor subunit GluA2 and colocalizes with AMPA receptors both at synapses and extrasynaptic sites 1. Unlike traditional AMPA receptor auxiliary subunits, SYNDIG1 does not alter AMPA receptor gating, pharmacology, or surface trafficking 2. Instead, it regulates excitatory synaptogenesis by controlling the number of functional excitatory synapses, affecting both AMPA and NMDA receptor-mediated transmission 2. The protein's activity is regulated by neuronal activity, with its content in dendritic spines being activity-dependent 1. SYNDIG1 belongs to the dispanin family of transmembrane proteins involved in CNS synapse development and neurotransmitter release regulation 3. In disease contexts, SYNDIG1 has been implicated in cancer prognosis models and Alzheimer's disease risk through epigenetic mechanisms, with brain methylation levels at the SYNDIG1 locus associated with Braak stage progression 4. The protein represents a unique class of synaptogenic factors essential for proper excitatory circuit formation.