GRID1 encodes the glutamate delta 1 (GluD1) receptor, a member of the ionotropic glutamate receptor family that plays crucial roles in synaptic organization and neural development 1. Unlike classical glutamate receptors, GluD1 does not primarily bind glutamate but instead forms trans-synaptic adhesion complexes with presynaptic neurexins and cerebellin proteins, regulating both excitatory and inhibitory synaptic transmission 2. The receptor functions as a postsynaptic cell adhesion molecule that influences synaptic assembly and modulation across multiple forebrain regions including the striatum, hippocampus, and cortex 2. GluD1 also modulates metabotropic glutamate receptor (mGlu1/5) signaling pathways and affects dendritic morphology and excitatory synapse density 3. Disease relevance is significant, as GRID1 genetic variants are associated with multiple neuropsychiatric conditions including schizophrenia 4 5, intellectual disability with spastic paraplegia 3, bipolar disorder, and depression 6. Pathogenic variants can disrupt cerebellin binding, impair mGlu receptor signaling, or create constitutively active receptors 1 3. These findings establish GRID1 as a critical synaptic organizer whose dysfunction contributes to various neurodevelopmental and psychiatric disorders through disrupted synaptic connectivity and signaling.