A bat epigenetic clock

This 2021 study subject was bats:

“Exceptionally long-lived species, including many bats, rarely show overt signs of aging, making it difficult to determine why species differ in lifespan. Here, we use DNA methylation (DNAm) profiles from 712 known-age bats, representing 26 species, to identify epigenetic changes associated with age and longevity.

Hypermethylated age- and longevity-associated sites are disproportionately located in promoter regions of key transcription factors (TF) and enriched for histone and chromatin features associated with transcriptional regulation. Predicted TF binding site motifs and enrichment analyses indicate that:

  • Age-related methylation change is influenced by developmental processes, while
  • Longevity-related DNAm change is associated with innate immunity or tumorigenesis genes, suggesting that
  • Bat longevity results from augmented immune response and cancer suppression.

Molossus molossus [a short-lived species] age genes are not enriched for immunity genes or genes that frequently mutated in cancer. However, M. molossus longevity genes exhibit significant overlap with genes involved in immunity and genes frequently mutated in human tumors.

Similar overlap patterns among immunity, longevity, and tumor-mutated genes also exist for long-lived bats.

Two species’ genetic adaptations for tumor suppression have been described to help explain their extreme longevity. Bats also have genetic mechanisms that enable strong antiviral immune responses without inducing damaging inflammatory reactions that may enable them to tolerate high levels of viral exposure.

Our results are consistent with an epigenetic clock theory of aging that connects beneficial developmental and cell maintenance processes to detrimental processes causing tissue dysfunction.”

https://www.nature.com/articles/s41467-021-21900-2 “DNA methylation predicts age and provides insight into exceptional longevity of bats”

The founder of the epigenetic clock has been busy, coauthoring more published studies than there have been weeks in this year! I’ve read five other 2021 studies he’s coauthored on dogs, horses, mammals (2), and humans in DNA methylation biomarker for cumulative lead exposure is associated with Parkinson’s disease. This one stood out for its “longevity results from augmented immune response and cancer suppression” findings.

If we’re interested in longevity, this clarity can direct efforts to both improve our immune systems and avoid problems like cancer. Symptoms may be subclinical, but that doesn’t provide adequate rationale to not address causes.

Peer review comments and responses were informative:

Reviewer #1 – “Developing an aging clock that works for a diverse set of bat species is a spectacular achievement.”

Reviewer #2 – “This is a tour de force study.”

Replies to Reviewer #3:

“Difference in recorded lifespans between three long-lived species and two short-lived species that we used to identify longevity DMPs [differentially methylated positions] is 20 years or more, even though they have similar body sizes (20-40 g). The three long-lived species [maximum ages 29.9, 30.5, and 37.1 years] also represent three different phylogenetic lineages.

CpG sites that undergo hypomethylation with age do so largely at random. In contrast, sites that undergo hypermethylation with age are highly nonrandom, and as has been noted before, are near genes associated with development. So yes, we believe there are predictable methylation changes with age.”

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