MAPK3 is a serine/threonine kinase that is an essential member of the MAP kinase signal transduction pathway (MAPK/ERK cascade). MAPK3 is required for proper targeting of presynaptic axons to postsynaptic targets, and MAPK3 mutations or dysfunction may induce the formation of abnormal neuronal architecture and contribute to the pathogenesis of autism spectrum disorder and other neuropsychiatric disorders. In immunohistochemistry, MAPK3 has cytoplasmic positivity in cells throughout the central nervous system and is found in most other tissues in the body. References: Mol Cells. 2017 Feb 28; 40(2): 151–161, PMID: 28196412; Int J Dev Neurosci. 2014 Dec;39:2-8, PMID: 24631207;