The major phenotypes of DiGeorge syndrome can potentially be explained by TBX1 haploinsufficiency, with other symptoms attributed to the cumulative effects from loss of other 22q11.2 genes (Jerome and Papaioannou, 2001; Lindsay et al., 2001; Paylor et al., 2006; Yagi et al., 2003). This evidence concerns the gene TBX1 and 22q11.2 deletion syndrome.