Although highly penetrant genetic risk factors for autism are individually rare, we can group them together to gain broader understanding of important mechanisms in autism pathophysiology. Our past work includes investigating GxG and modifier effects utilizing diseases caused by genes in the Ras-MAPK signaling pathway (RASopathies) and (relatively) common CNVs such as in the 16p11.2 and 22q11.2 regions. We hope to apply these approaches to potential autism biomarkers such as brain growth (trajectory) in order to understand better whether (and to what extent) known macrocephaly/microcephaly mechanisms contribute to autism.