ERBB4 and psychiatric disorder: Stage T3 was also enriched for nervous system development (FDR = 6 × 10–12; e.g., ERBB4) and projection morphogenesis (FDR = 1 × 10–9; e.g., SEMA6D), and was most specifically marked by GRIA2, a glutamate ionotropic receptor subunit implicated in multiple mental disorders.