The other four genes regulate sister chromatid cohesion, affecting cohesin subunits SMC1–SMC1L1, SMC3–CSPG6, SCC3–STAG3 and cohesin-loading complex subunit SCC2–NIPBL, implying that cohesion gene mutations are enriched in colorectal cancers (Barber et al., 2008). This evidence concerns the gene SMC1A and colorectal cancer.