Seckel syndrome is an autosomal recessive disorder involving dwarfism and mental retardation. In an Advance Online Publication in Nature Genetics O'Driscoll et al. report the discovery of a mutation in the DNA-repair kinase ATR, in Seckel syndrome patients (NatureGenetics, 17 March 2003, doi:10.1038/ng1129). The ATR (ataxia-telangiectasia and Rad3-related) gene mapped to chromosome 3q22.1-q24, which had been genetically linked to Seckel syndrome. Fibroblasts from patients had impaired ATR function and response to ultraviolet radiation. O'Driscoll et al. identified a synonymous mutation that affects ATR splicing, and that causes reduced ATR protein levels. This is the first report linking ATR signalling to a clinical disorder.