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Review
. 2000 Nov 7;97(23):12407-8.
doi: 10.1073/pnas.210382097.

Aging mechanisms

Y Takahashi  1 , M Kuro-O, F Ishikawa
Affiliations
Review

Aging mechanisms

Y Takahashi et al. Proc Natl Acad Sci U S A. .

Abstract

Aging (senescence) has long been a difficult issue to be experimentally analyzed because of stochastic processes, which contrast with the programmed events during early development. However, we have recently started to learn the molecular mechanisms that control aging. Studies of the mutant mouse, klotho, showing premature aging, raise a possibility that mammals have an "anti-aging hormone." A decrease of cell proliferation ability caused by the telomeres is also tightly linked to senescence. Frontier experimental studies of aging at the molecular level are leading to fascinating hypotheses that aging is the price we had to pay for the evolution of the sexual reproduction system that produces a variety of genetic information and complex body structures.

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Figures

Figure 1
Figure 1
A mutant model mouse is useful for studies of aging. The klotho phenotype (premature aging) is caused by a disruption of the single gene, klotho.
Figure 2
Figure 2
The linear chromosomes of all of the eukaryote cells have the telomeres at both ends. As the cells continue to prolifereate, the length of the telomeres shortens and ultimately the cells stop dividing.
Figure 3
Figure 3
A hypothesis that Klotho protein itself may be a humoral factor. A part of the extracellular domain of Klotho protein could be liberated into the extracellular space either through proteolytic cleavage or through alternative RNA splicing. Klotho protein may be secreted into the blood stream and function as an “anti-aging” hormone (4).
Figure 4
Figure 4
Telomeres and meiosis. Two fission yeast cells undergo mating and meiosis by a series of steps: a, mating; b, kissing; c, cell and nuclear fusion followed by oscillating movement of the nucleus; and d, spore formation. At step c, two homologous chromosomes need to be paired. This pairing is accomplished is accomplished by colocalization of all of the telomeres at SPB, and dynamic movement of chromosomes led by SPB (11).
Figure 5
Figure 5
Comparison between the eukaryotes that have the linear chromosomes and telomeres and the prokaryotes that have the circular chromosome in respect of aging, sex, and complexity of the organisms.
See this image and copyright information in PMC

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