With this in mind, a series of CNV studies have been carried out to look systematically for non-Mendelian causes of ASD, focusing on de novo mutations. In 2007, Sebat et al. investigated the global frequency of de novo CNVs in trios (i.e., child-mother-father), comparing the frequencies of mutations in offspring between sporadic cases of ASD (i.e., “simplex” families with only a single affected offspring), familial cases (i.e., “multiplex” families with multiple affected offspring) and healthy control offspring (Sebat et al., 2007). In this study, a high rate of de novo CNVs in idiopathic ASD cases from simplex families (10%) was observed compared to the rate in cases from multiplex families (2%) or unaffected controls (1%). The striking 10-fold higher rate of mutations in cases suggested that a majority of mutations identified were contributing to risk.
