COG2 (component of oligomeric Golgi complex 2) is a subunit of the conserved oligomeric Golgi (COG) complex, a multi-subunit vesicle tethering complex essential for Golgi apparatus structure and function 1. COG2 functions as part of the COG complex, which mediates retrograde vesicular trafficking within the Golgi apparatus and is required for normal Golgi morphology 2. The complex plays critical roles in protein and lipid glycosylation and protein sorting 3. Structurally, COG2 is incorporated into the complex through direct interactions with COG1, COG3, and COG4, which serves as a core organizational component 4. COG2 mutations cause congenital disorder of glycosylation type 2Q (CDG-2Q), a severe genetic disorder characterized by defects in glycoprotein sialylation and galactosylation 5. Patients with COG2 mutations present with microcephaly, psychomotor retardation, seizures, liver dysfunction, and copper metabolism abnormalities 5. The disease mechanism involves impaired retrograde trafficking of Golgi resident proteins, disrupting normal Golgi structure and glycosylation capacity 2. Understanding COG2 function is clinically significant as it explains how COG complex defects cause congenital glycosylation disorders affecting multiple organ systems.