Consequences of telomere shortening during lifespan

► Telomeres shorten with age in humans. ► Whether the consequences of telomere dysfunction in naturally ageing individuals is the limiting factor in maintenance of tissue homeostasis, therefore directing the ageing phenomena is not known. ► Most studies in the lab use mouse models that do not rely on telomeres as a cell division control mechanism. ► It is timely to identify complementary vertebrate models that, like humans, have restricted telomerase activity and have telomere length as a cell division clock.