A total of six quantitative trait loci, meeting genome-wide significance for three autism relevant behaviors in BTBR, were identified on chromosomes 1, 3, 9, 10, 12, and X. Moreover, in a recently published biochemical evaluation of BTBR mice, the authors identified upregulation of the ERK signaling pathway in the newborn mice, suggesting, but not demonstrating directly, that this elevation in Erk activation was linked with the autistic behavior in BTBR [14]. Here, MAPK1 is linked to autism.