 Transgenic gene knockout mice lacking MAPK1 have major defects in early development.Apart from developmental defects, under activity or lack of MAPK1 (Erk2) resist activation induced cell death in helper T cells which could cause autoimmunity due to T helper 17 persistence.Mitogen-activated protein kinase 3 (MAPK3) is also known as "extracellular signal-regulated kinase 1" (ERK1).