John Sedivy is a Hermon C. Bumpus Professor of Biology, and an Associate Dean and Director of the Center for the Biology of Aging at Brown University. He has a long-standing interest in mammalian genetics, signalling and cell cycle control. His achievements include developing one of the first methods for targeted homologous recombination, generating the first viable knockout of c-Myc in rat fibroblast cells, achieving the first homozygous gene knockout (CDKN1A) in primary human cells, which led to the discovery that p21 is a key regulator of entry into cellular senescence, and showing that cellular senescence is regulated in parallel by the p53-p21 and p16-pRb pathways. In 2004 his lab developed an assay for dysfunctional telomeres as a single-cell biomarker of senescence and delineated the signalling pathway between dysfunctional telomeres and the cell cycle. This led to the first in vivo quantification of cellular senescence in ageing primates. His other discoveries include the finding that retrotransposons are activated with age in somatic cells, and that retrotransposon LINE-1 activation triggers host interferon and innate immune responses. Currently, John Sedivy is a Scientific Advisory board member at Longaevus Technologies.