MAPK1 and Leber congenital amaurosis: To gain insight into the modulatory pathways that are responsible for the decreased CD4+ Th cell activation by LCA, we investigated the activation status of Mitogen-activated protein kinases (MAPK), Extracellular signal-regulated kinase (ERK)-1/2, c-Jun N-terminal kinase (JNK)-1/2 and P38 mitogen-activated protein kinase (P38) that are crucial in CD4+ Th cell activation [23].