Cooperative role of CD81 with GPR56 and collagen III in cortical formation

The ADGRG1 gene encodes GPR56, an adhesion G-protein-coupled receptor essential for neuronal migration during cortical development. GPR56 interacts with extracellular matrix components such as collagen III, integrin α3β1, and tetraspanins CD81/CD9. While prior studies demonstrated cortical dysplasia in collagen III single knockout and GPR56/Itga3 double knockout mice, the role of CD81 in brain development remains unclear. This study investigates the functional interaction between CD81 and GPR56 in the embryonic brain. We found CD81 highly expressed in apical and basal regions and the meninges of the developing neocortex. CD81 was detected with GPR56 in neurons and astrocytes and expressed in collagen III + meningeal fibroblasts (MFs) and CD34 + endothelial cells. CD81 directly interacted with GPR56 in neurons and with collagen III in MFs. In neurons, CD81 was required for collagen III-induced activation of the GPR56-RhoA signaling pathway. In MFs, CD81 depletion reduced vimentin and collagen III levels, indicating impaired meningeal integrity. Notably, Gpr56/Cd81 double knockout mice exhibited severe frontal brain malformations, including neuronal over-migration and cortical dyslamination. These findings show a cooperative role of CD81 with GPR56 and collagen III in both neural and meningeal compartments, contributing to proper cortical formation during embryonic development. • CD81 physically associates with GPR56 in the neocortex • CD81 plays a pivotal role in neuronal migration by collagen III through the activation of the GPR56-RhoA signaling pathway • CD81 contributes to maintaining the cell integrity of MFs by modulating collagen III expression and cellular morphology