Abstract
The transposon theory of aging hypothesizes the activation of transposable elements (TEs) in somatic tissues with age, leading to a shortening of the lifespan. It is thought that TE activation in aging produces an increase in DNA double-strand breaks, contributing to genome instability and promoting the activation of inflammatory responses. To investigate how TE regulation changes in somatic tissues during aging, we analyzed the expression of some TEs, as well as a source of small RNAs that specifically silence the analyzed TEs; the Drosophila cluster named flamenco. We found significant variations in the expression levels of all the analyzed TEs during aging, with a trend toward reduction in middle-aged adults and reactivation in older individuals that suggests dynamic regulation during the lifespan.
Highlights
The flamA strain showed a high gypsy expression level and low ZAM and Idefix levels, while wIR6RevII7 strain showed a high Idefix expression level and low gypsy and ZAM expression levels (Figure 1A). These data confirm that gypsy and Idefix are upregulated in the head when there is a specific permissive allele of flamenco, to what happens in ovaries
RT-quantitative PCR (qPCR) experiments have confirmed that gypsy is strongly upregulated, while flamenco is downregulated in the ovary [1]
Retrotransposon down- and up-regulation has been described for the Drosophila Copia element in adult testis, in which it is down regulated in 12–15-day-old tissues with respect to three-day-old tissues and again upregulated at 24–27 days [22]
Summary
A well-characterized line permissive for the mobilization of ZAM and Idefix (Rev line) displays large deletions that remove ZAM and Idefix sequences in the flamenco locus [6] This allows ZAM and Idefix expression in the follicular epithelium and in somatic tissues outside the ovary throughout Drosophila development (in embryos, larvae and adult flies) [7]. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations These mechanisms have been investigated, nothing is known about what happens to the expression of small RNA clusters in aging, and whether there is a correlation with changes in the expression levels of the regulated TEs. Increased mobilization of some TEs in somatic tissues during aging has been considered to be a cause of lifespan-shortening, and the observation of this phenomenon is at the base of the “transposon theory of aging” [11,12]. This finding supports a possible correlation between gypsy activation and longevity
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