The best characterized cohesinopathy is CdLS, an autosomal dominant (NIPBL, SMC3, and RAD21) or X-linked (SMC1A and HDAC8) malformation syndrome (Krantz et al., 2004; Tonkin et al., 2004; Musio et al., 2006; Deardorff et al., 2007; Deardorff et al., 2012a; Deardorff et al., 2012b; Harakalova et al., 2012). Here, RAD21 is linked to Cornelia de Lange syndrome.