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Senescence of cultured human diploid fibroblasts. Are mutations responsible?
Author(s) -
Gupta Radhey S.
Publication year - 1980
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041030206
Subject(s) - mutagen , senescence , methane sulfonate , biology , microbiology and biotechnology , mutation , mutation frequency , genetics , population , mutant , somatic cell , ploidy , gene , lymphocyte , ethyl methanesulfonate , diphtheria toxin , toxin , dna , demography , sociology
Abstract Two predictions of the error/mutation hypothesis of cellular sensecence (Orgel, '73) namely, (a) exponential accumulation of somatic mutations during the replicative lifespan and (b) shortening of culture lifespan upon treatment with mutagens have been examined experimentally in a strain of cultured human diploid fibroblasts. Our studies show that as cells traverse the replicative lifespan (from 10 to 75 mean population doublings (MPD); total lifespan ⋍ 95 MPD), no rapid and exponential increase occurs in the accumulation of mutations measured by the frequencies of Thg r (thioguanine resistance) and Dip r (diphtheria toxin resistance) mutants. Furthermore, repeated cycles of treatment (from 1‐ to 14‐times) of human fibroblasts with two mutagens, ethyl methane sulfonate (EMS) and N‐methyl‐N′nitro‐nitrosoguanidine, which led to a marked increase in the mutation frequency for the Dip r marker (⋍ 100‐fold), failed to shorten the lifespan of cultured fibroblasts. On the contrary, repeated mutagen treatment (12 times with EMS) prolonged the lifespan of one replicative culture (110 MPD versus 94–98 MPD). These results strongly indicate that mutations are unlikely to be the primary event in cellular senescence and suggest instead that senescence is probably controlled by one or more (specific) gene(s) whose expression can be modified by mutations.