In man, the mild forms of CdLS that have been linked to mutations in cohesin subunit genes (Smc1 and Smc3 [61],[62]) appear to be caused by specific, rare missense mutations (i.e., very likely not simple loss-of-function alleles), also consistent with the idea that the cause of CdLS is not simply a reduced level of cohesin function, but rather the selective disruption of specific functions in which Nipbl and cohesin work together. The gene discussed is SMC1A; the disease is Cornelia de Lange syndrome.