Figure 6

Model of gene expression patterns associated with extended longevity. Age-related gene expression of C and SR flies for (A) stress- and (B) reproduction-related genes. The expression pattern associated with normal ageing typically involves a strong upregulation of genes involved in stress responses. This reflects an activation of repair mechanisms counteracting the cellular damage associated with ageing. In long-lived individuals, genes involved in stress response and repair show generally a higher expression. The difference in expression is higher at younger age classes, as the normal-lived individuals upregulate those genes stronger with age. Another typical characteristic of age-dependent expression in normally-ageing individuals is a strong decline in genes involved in reproduction, which reflects ceasing reproductive activity at older age. Individuals with extended lifespan often show lower expression levels of those genes at younger age classes as compared to normal-lived controls, but their expression is maintained longer at relatively high levels. While the model generally reflects the existing expression data, some studies detected different patterns. For example, Sarup et al. [38] reported that the males of the lines selected for reproductive longevity showed on average higher expression of genes involved in cell cycle and biogenesis (reproduction-related genes) and a lower expression of the genes involved in immune functions (stress related genes). The proposed model might be more representative for females, where the reproductive activity is more directly reflected in gene expression. Also, the model is likely to refer to the expression patterns observed at the whole body level better than to those observed in specific tissues.