Experimental manipulation of telomere length: does it reveal a corner-stone role for telomerase in the natural variability of individual fitness?
Résumé
Telomeres, the non-coding ends of linear chromosomes, are thought to be an
important mechanism of individual variability in performance. Research
suggests that longer telomeres are indicative of better health and increased fitness;
however, many of these data are correlational and whether these effects
are causal are poorly understood. Experimental tests are emerging in medical
and laboratory-based studies, but these types of experiments are rare in natural
populations, which precludes conclusions at an evolutionary level. At the
crossroads between telomere length and fitness is telomerase, an enzyme
that can lengthen telomeres. Experimental modulation of telomerase activity
is a powerful tool to manipulate telomere length, and to look at the covariation
of telomerase, telomeres and individual life-history traits. Here, we review
studies that manipulate telomerase activity in laboratory conditions and
emphasize the associated physiological and fitness consequences. We then
discuss how telomerase’s impact on ageing may go beyond telomere maintenance.
Based on this overview, we then propose several research avenues for
future studies to explore how individual variability in health, reproduction
and survival may have coevolved with different patterns of telomerase activity
and expression. Such knowledge is of prime importance to fully understand
the role that telomere dynamics play in the evolution of animal ageing.
This article is part of the theme issue ‘Understanding diversity in
telomere dynamics’.