RAD21 and Cornelia de Lange syndrome: Supporting this, Deardorff et al. found haploinsufficiency for RAD21 led to approximately halved RAD21 RNA in a cell line from a patient with classical CdLS, while haploinsufficiency for NIPBL is often associated with a compensatory upregulation of RNA levels, presumably from the intact allele (Borck et al. 2006; Deardorff et al. 2012; Newkirk et al. 2017).