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Pan-mammalian analysis of molecular constraints underlying extended lifespan.

ABSTRACT: Although lifespan in mammals varies over 100-fold, the precise evolutionary mechanisms underlying variation in longevity remain unknown. Species-specific genetic changes have been observed in long-lived species including the naked mole-rat, bats, and the bowhead whale, but these adaptations do not generalize to other mammals. We present a novel method to identify associations between rates of protein evolution and continuous phenotypes across the entire mammalian phylogeny. Unlike previous analyses that focused on individual species, we treat absolute and relative longevity as quantitative traits and demonstrate that these lifespan traits affect the evolutionary constraint on hundreds of genes. Specifically, we find that genes related to cell cycle, DNA repair, cell death, the IGF1 pathway, and immunity are under increased evolutionary constraint in large and long-lived mammals. For mammals exceptionally long-lived for their body size, we find increased constraint in inflammation, DNA repair, and NFKB-related pathways. Strikingly, these pathways have considerable overlap with those that have been previously reported to have potentially adaptive changes in single-species studies, and thus would be expected to show decreased constraint in our analysis. This unexpected finding of increased constraint in many longevity-associated pathways underscores the power of our quantitative approach to detect patterns that generalize across the mammalian phylogeny.

SUBMITTER: Kowalczyk A

PROVIDER: S-EPMC7012612 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Pan-mammalian analysis of molecular constraints underlying extended lifespan.

Kowalczyk Amanda A Partha Raghavendran R Clark Nathan L NL Chikina Maria M

eLife 20200211

Although lifespan in mammals varies over 100-fold, the precise evolutionary mechanisms underlying variation in longevity remain unknown. Species-specific genetic changes have been observed in long-lived species including the naked mole-rat, bats, and the bowhead whale, but these adaptations do not generalize to other mammals. We present a novel method to identify associations between rates of protein evolution and continuous phenotypes across the entire mammalian phylogeny. Unlike previous analy ...[more]

PMID: 32043462

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Project description:We have previously reported that tyrosol (TYR), one of the main phenols in extra virgin olive oil (EVOO), promotes lifespan extension in the nematode Caenorhabditis elegans, also inducing a stronger resistance to thermal and oxidative stress in this animal model. Although the influence of several longevity-related genes in these effects has been reported by our group, we decided to perform a whole genome DNA-microarray approach in order to identify other genes and molecular pathways further involved in TYR effects on C. elegans longevity. Microarray analysis identified 208 differentially expressed genes (206 overexpressed and 2 underexpressed) when comparing TYR-treated nematodes with non-treated controls. Many of these genes seem linked to processes such as regulation of growth, transcription, reproduction, lipid metabolism and body morphogenesis. Data obtained by microarray was validated by qRT-PCR analysis of selected genes. Our results confirm that several important cellular mechanisms related to longevity are influenced by TYR treatment in this animal model. Moreover, we detected an interesting overlap between the expression pattern elicited by TYR and those induced by other dietary polyphenols known to extend lifespan in C. elegans, such as quercetin and tannic acid. C. elegans were maintained on Nematode Growth Medium (NGM) and E. coli OP50 as described [21]. For microarray experiments, fer15(b26) nematodes were synchronized by hypochlorite treatment and raised at 25°C on NGM plates containing either 250 μM TYR (n=3) or vehicle (control; n=3). At the fourth day of adulthood, nematodes were collected from the plates in M9 buffer, washed 3 times and pelleted by centrifugation for RNA isolation. After centrifugation, worms were resuspended in 350 μl of RLT/BME buffer, flash frozen in liquid nitrogen and thawed at 37 °C three times for disruption and total RNA was extracted using the RNeasy Mini Kit (Qiagen) following the manufacturer recommended protocol. Final volume of isolated RNA was 50 μl per biological sample. RNA quality was analyzed with the 2100 Bioanalyzer (Agilent Technologies) using the RNA 6000 nano kit. All RNA samples were of sufficient quality for gene array analysis with RIN>7. A total amount of 50 ng of RNA was used as the template for cDNA synthesis and in vitro transcription to synthesized biotin-modified aRNA using the GeneChip® 3’ IVT Express Kit (Affymetrix, 901228). aRNA was purified from unincorporated nucleotides and other reaction components using the RNeasy Mini Kit (Qiagen). A total of 15 µg of biotin-labeled aRNA was fragmented following the instructions described in the Affymetrix manual (P/N 702646 Rev.8) and hybridized to C. elegans GeneChip® Genome Arrays (Affymetrix, 900383). They were processed and scanned using Affymetrix instrumentation and with hybridization, washing and scanning parameters provided by the manufacturer. Computational and statistical analyses were carried out using the R software (http://www.r-project.org/) and the appropriate Bioconductor packages (http://www.bioconductor.org/) run under R. In order to remove all the possible sources of variation of a non-biological origin between arrays, densitometry values between arrays were normalized using the RMA (robust multiarray) normalization function implemented in the Bioconductor affylmGUI. Statistically significant differences between groups were identified using the rank product non-parametric test implemented in the Bioconductor Rank-Prod package. Those genes showing a corrected (FDR) p-value < 0.05 were selected as significant.

Dataset Information

Pan-mammalian analysis of molecular constraints underlying extended lifespan.

Publications

Pan-mammalian analysis of molecular constraints underlying extended lifespan.

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