George Martin laid much of the groundwork for the WRN locus positional cloning effort in Seattle by developing the Werner Syndrome International Registry in 1992 [15]; by assembling a growing collection of clinical material developed in collaboration with Japanese and other colleagues; and by facilitating the development and use of homozygosity mapping to convert an initial linkage assignment of WRN to chromosome 8 into molecular clones that enabled gene finding and the identification of putative loss of function mutations, as predicted by the formal WS recessive inheritance pattern [16,17]. This evidence concerns the gene WRN and Werner syndrome.