Several possibilities could explain the aberrant expression of ATM in Q3SC. Exon skipping has been observed in several genes (Dutertre et al., 2010, Nevo et al., 2012) and is believed to be influenced by ATM function (Tresini et al., 2015). By amplifying cDNA with PCR primers targeting sites outside of exons which contain mutations in Q3 (sequences found in Table S1), only full-length product was identified, providing no evidence for mRNA skipping those exons (Figure 1G). We also counted the frequencies of sequenced, cloned PCR products corresponding to each allele and found only the c.7792 C > T allele mixed with wild-type sequence in Q3SC: there was no evidence of the c.217_218 delGA allele in the mRNA, as was found in CAR3 (Figure 1H). This would be consistent with gene reversion, because a simple deletion could not generate a wild-type allele.
