MAPK3 as a Chr 16p11.2 Autism Candidate Gene

The chromosomal region of 16p11.2 has emerged from genetic screening in humans as a significant susceptibility locus for ASD. This interval contains 25 genes; however, the link between these genes and the symptoms of ASD is not clear. Dr. Page’s research sought to bridge this gap in our understanding by investigating the role of candidate genes from the 16p11.2 region in the development of brain and behavior, using the mouse as a model system. The first candidate gene he focused on was MAPK3. Dr. Page selected this gene as a candidate for the following reasons: 1) He previously found that ERK, the Drosophila homologue of MAPK3, influences regionalized growth in the embryonic brain by controlling proliferation of specific populations of neural stem cells in response to activation of the receptor tyrosine kinase EGFR in these cells (Page, 2003), 2) MAPK3 is know to act in the PTEN/PI3K pathway to influence a variety of cellular processes relevant to growth (Cully et al., 2006). Dr. Page has found that haploinsufficiency for Pten leads to brain overgrowth as well as social behavioral deficits (Page et al., 2009), two phenotypes relevant to ASD. And, 3) MAPK3 acts in several additional pathways that have been implicated in ASD pathogenesis, including: Serotonin (Launay et al., 1996), Oxytocin (Blume et al., 2008) and IL-6/immune signaling (D’Arcangelo et al., 2000). Dr. Page’s studies indicate that Pten intersects with these pathways in the developing brain. Thus, the possibility that MAPK3 might act as an intermediary across these pathways is one worth exploring. As an initial investigation of the function of Mapk3 in ASD-relevant endophenotypes, Dr. Page made use of assays of social approach behavior and brain growth.