ZEB2 and cancer: High levels of clustering are found in introns of other genes, including SMA4 (16 clusters on Chr5), a complex 900 kb long locus annotated as a pseudogene, and ZEB2 (9 clusters on Chr2), a protein-coding gene that is down-regulated in a variety of cancers [16–18] and is a causal factor in the developmental disorder, Mowat-Wilson syndrome [19].