Telomeres are structural ends of eukaryotic chromosomes and are composed of telomeric repeats and associated proteins. One of the functions of telomeres is to prevent chromosome ends from being recognized as double-stranded breaks and to protect them from fusion and degradation. Telomere length affects telomere function because a minimal telomere length is required for the formation of a proper telomere structure, and telomere length may influence the equilibrium between the 'closed' and the 'open' states, which may be subjected to different enzymatic activities (eg telomerase). Terminal restriction fragment (TRF) analysis is the only method currently available for measuring telomere length in Caenorhabditis elegans . Its limitations include low sensitivity and interference by the presence of interstitial telomeric sequences in the C. elegans genome. Here we report the adaptation of single telomere length analysis (STELA) to measure the length of telomere repeats on the left arm of chromosome V in C. elegans. This highly sensitive PCR based method allows telomere length measurement from as few as a single worm. The application of STELA to eight wildtype C. elegans strains revealed considerable strain-specific differences in telomere length. Within individual strains, short outlying telomeres were observed that were clearly distinct from the bulk telomere length distributions, suggesting that processes other than end-replication losses and telomerase-mediated lengthening may generate telomere length heterogeneity in C. elegans. The utility of this method was further demonstrated by the characterization of telomere shortening in
mrt-2 mutants. We are currently using STELA to study different mutants for telomere phenotypes.