However, we cannot exclude the possibility that haploinsufficiency for other genes within the 20q CDR cooperates with aberrantly low expression of MYBL2 to move the cells toward malignant transformation, as has been shown for the CDR associated with the 5q-syndrome, where haploinsufficiency of the gene RPS14 as well as loss of expression of an miRNA (Ebert et al., 2008; Barlow et al., 2010; Starczynowski et al., 2010) are critical steps in MDS pathogenesis. The gene discussed is MYBL2; the disease is myelodysplastic syndrome associated with isolated del(5q).