Gene Expression Becomes Heterogeneous With Age In Humans And Rats

May 24, 2006

In a study of the effects of aging on gene expression, researchers

have found that variation in gene expression among individuals tends

to increase with age. The findings, which impact our understanding of

the molecular forces that govern age-related changes, are reported in

the May 23rd issue of Current Biology by Mehmet Somel and colleagues

at the Max Planck Institute for Evolutionary Anthropology and the

University of Cambridge.

One long-standing observation concerning the physiological decline

that accompanies aging is its variability--some people age better

than others. However, there has thus far been little or no evidence

supporting the existence of similar heterogeneity at the level of

gene expression. Lack of such evidence, in turn, gives support to

a " programmed aging " hypothesis and argues against the more commonly

accepted " stochastic aging " model, in which random biological events

play an important role.

In the new work, researchers put to the test the question of whether

gene-expression heterogeneity increases with age. Using a wide range

of expression data from both humans and rats, the researchers showed

that levels of gene expression become more variable with age.

Furthermore, they found that the tendency toward increased variation

is not restricted to a specific set of genes, implying that increased

heterogeneity is the outcome of random processes such as genetic

mutation.

These observations corroborate the notion that aging is underpinned

by stochastic events. That said, the authors of the study point out

that the observed increases in expression variation are surprisingly

small, leaving plenty of room for further explanations regarding the

relationship between aging-related changes at the organismal level

and the underlying molecular mechanisms of aging. Nevertheless, the

new results show that with the increasing amounts of molecular data

available to researchers, scientists will now experience improved

opportunities to answer age-old questions about the nature of aging.

Mehmet Somel, Philipp Khaitovich, Svante Pääbo, and Lachmann

of the Max Planck Institute for Evolutionary Anthropology in Leipzig,

Germany; Sabine Bahn of the University of Cambridge in Cambridge,

United Kingdom.

Somel et al.: " Correspondence: Gene expression becomes hetergeneous

with age. " Publishing in Current Biology 16, R19-20, May 23, 2006.

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