In a seminal series of decisive studies, enforced expression of TERT, the catalytic subunit of telomerase, in cultured human fibroblasts stabilized telomere length and endowed the cells with unlimited replicative potential without engendering malignant properties43,44. The remarkable capacity of experimentally induced telomerase activity to circumvent senescence and allow indefinite growth has been documented in many other human cell types. These compelling cell culture studies and complementary studies in telomerase knockout mice (see below) have since inspired significant efforts to determine whether telomere dynamics bear relevance to the processes of ageing and/or various degenerative diseases in humans.
