Observations from mitogen-activated protein (MAP) kinase knockout animals
| Phenotype | |
| ERK1 | Viable; possible prolonged neuronal synapse |
| ERK2 | Lethal D11; failure of placental development; ERK2 knockdown fibroblasts do not proliferate in vitro |
| ERK5 | Lethal D10; endothelial cell failure and vascular leakage in conditional knockout |
| JNK1 | Viable; defect in Th1 differentiation; reduced osteoclastogenesis; sensitivity to induced dermal tumorigenesis; insulin resistance |
| JNK2 | Viable; defect in Th1 differentiation; reduced arthritic joint destruction; resistance to induced dermal tumorigenesis |
| JNK1+JNK2 | Lethal D16; failure in late-stage brain/CNS development; fibroblasts show reduced proliferation in vitro; resistant to physical-stress-induced apoptosis; defective TNF-α-induced AP-1 activation |
| JNK3 | Viable; resistant to stress-induced neuronal apoptosis |
| p38α | Lethal D11; defect in angiogenesis |
| Cells resistant to apoptosis induced by Fas; increased transformation in presence of activated Ras; defect in MAPKAPK-2 activation and TNF-α, IL-1 and IL-6 expression | |
| p38β | Viable; no defects observed in the immune responses studied |
| p38γ | Not reported |
| p38δ | Not reported |
Details of the knockouts are as follows: extracellular signal-regulated kinase (ERK) 1 1, ERK2 2, ERK5 3, c-Jun N-terminal kinase (JNK) 1 4–6, JNK2 7–10, JNK1/2 11, JNK3 12, p38α 13, and p38β 14. Th: T-helper cell; CNS: central nervous system; TNF: tumour necrosis factor; AP: activator protein; MAPKAPK: mitogen-activated protein kinase activated protein kinase; IL: interleukin.