Telomere length (TL) is considered an indicator of cellular health in both clinical and research settings (1). Current techniques to measure TL lack sensitivity and are unable to provide the distribution of individual TLs in a cell population (2). This is particularly problematic, as it is the proportion of short telomeres, rather than average TL, that triggers cellular senescence (3).
We have developed a novel technique called telomere fibre-FISH (TFF) that involves applying DNA fibres (4) using a constant stretching factor of 2 kb/μM onto silanized microscope slides and using a fluorescently-labelled telomere-specific probe to precisely measure individual TLs. We have validated TFF against other TL measurement techniques, including TRF, flow-FISH, Q-FISH, and qPCR. TL correlated across the methods (R2 = 0.78 – 0.93), with TFF providing higher resolution imaging and more detailed information regarding the distribution of individual TLs. We have demonstrated that TFF can accurately measure dynamic changes in TL in mortal cells as they approach senescence, and in cancer cells following manipulation of telomere maintenance pathways (5, 6). TFF was used to measure TL in 12 healthy individuals, and in 5 patients previously diagnosed with telomere biology disorders (7, 8). Specifically, TFF identified strikingly short TL distributions in the patient samples, with mean TLs that were noticeably lower than those of healthy individuals. Finally, we have developed software pipelines for the automated analysis of telomere length by TFF, demonstrating potential utility for high-throughput applications.
TFF is a simple and precise method for the measurement of TL, with several advantages over current techniques. These advantages include increased biological insight provided by the distribution of individual telomere lengths, versatility in sample preparation and starting material, and the ability to automate for unbiased high-throughput applications.