These results demonstrate that the SMC-3[K115E] substitution in C. elegans contributes towards developmental and behavioural defects without impacting on embryonic viability, mimicking the phenotype observed in CdLS patients and suggesting that the K114E in human SMC3 may contribute to the CdLS-like phenotypes observed in the heterozygous patient. Here, SMC3 is linked to Cornelia de Lange syndrome.