We first compared the case de novos with a set of control CNVs drawn from the same population as the trios. Although those CNVs must have originally occurred as de novo mutations, predominantly transmitted CNVs clearly have different characteristics from the case de novos, most obviously size. Although our set-based analyses allow for size differences, to ensure our findings were robust to the control data set, we also compared gene sets hit by case de novo CNVs with those hit in random assignments of gene-hitting CNVs of the same size and obtained very similar gene-set enrichments. Finally, in order to exclude the possibility that our findings reflected general properties of de novo CNVs, we compared case de novo CNVs to two sets of control de novos, one drawn from the Icelandic population and the other from a much smaller sample of unaffected sibs of people with autism. Despite the wide disparities in the sources of the control CNVs, and the potential for different sources of bias, the results converge in pointing to the involvement of the synapse, the PSD, and
