Lysosomes Rewrite the Epigenome to Pass Longevity Signals Across Generations
A lysosome-to-epigenome pathway in C. elegans extends lifespan across multiple generations via histone H3.3 transport from gut to germline.
Summary
Researchers at Baylor College of Medicine discovered that lysosomal metabolic signals extend lifespan not just in one organism but across multiple generations in C. elegans. Activating lysosomal lipid breakdown (via LIPL-4 overexpression), boosting lysosomal AMPK, or reducing mTOR signaling all increased expression of histone variant H3.3 (HIS-71) in the intestine and elevated H3K79 methylation genome-wide. Intestinal HIS-71 protein was then physically transported to the germline via vitellogenin-mediated yolk transport, where a germline-specific H3K79 methyltransferase (DOT-1.3) wrote heritable epigenetic marks. These changes propagated longevity benefits to descendants for up to three generations, establishing a soma-to-germline epigenetic communication axis.
Detailed Summary
Why this matters: A central question in aging biology is whether acquired longevity benefits can be inherited. This study demonstrates that metabolic signals originating in lysosomes can reprogram the epigenome in ways that are transmitted through the germline, extending lifespan across multiple generations in C. elegans. This has profound implications for understanding how environmental and metabolic states shape the health of future generations.
What was studied: The Wang lab used C. elegans to investigate how three distinct lysosomal signaling axes — lysosomal lipid signaling (LIPL-4 overexpression), lysosomal AMPK activation, and lysosomal mTORC1 suppression — influence histone modifications and transgenerational longevity. They employed lifespan assays, genome-wide ChIP-seq for multiple H3 methylation marks, RNA-seq, CRISPR tagging, tissue-specific protein degradation (auxin-inducible degron), RNAi knockdowns, and transgenic overexpression strategies across somatic and germline compartments.
Key results: All three lysosomal pathways converged on increasing H3K79 dimethylation and trimethylation genome-wide, particularly around transcription start sites. Integrated ChIP-seq and RNA-seq identified 42 transcriptionally upregulated genes with elevated H3K79me2/me3 marks in LIPL-4 transgenic worms, including the histone H3.3 variant gene his-71. The transcription factor SKN-1 (Nrf2 homolog) drove intestinal his-71 upregulation. Critically, HIS-71 protein was physically transported from the intestine to germline oocytes via vitellogenin lipoproteins and the RME-2 endocytic receptor. Blocking this transport — either by RNAi against rme-2 or vitellogenin genes, or by auxin-induced intestinal HIS-71 degradation — abolished the transgenerational longevity benefit. A germline-specific H3K79 methyltransferase, DOT-1.3, was required to write H3K79me2 marks in the germline and mediate heritable longevity. ChIP-seq confirmed elevated H3K79me2 persisted in wild-type descendants two generations after separation from the longevity-inducing ancestor. Overexpression of his-71 or dot-1.3 alone in the germline was sufficient to extend lifespan across generations.
Implications: This work establishes a mechanistic chain from lysosomal metabolic sensing → somatic epigenome (H3K79me) → histone variant (H3.3/HIS-71) upregulation → intestine-to-germline protein transport → germline epigenetic writing (DOT-1.3) → transgenerational longevity. It positions lysosomes not merely as degradative organelles but as master signaling hubs that communicate metabolic status to future generations through epigenetic inheritance.
Caveats: All experiments were performed in C. elegans, a genetically tractable but evolutionarily distant model from humans. Whether analogous lysosome-epigenome-germline signaling axes exist in mammals remains to be determined. The precise chromatin targets of H3K79 methylation that drive longevity gene expression programs were not fully resolved in this study.
Key Findings
- Lysosomal lipid signaling, AMPK activation, and mTOR suppression all increase H3K79me2/me3 genome-wide in C. elegans.
- LIPL-4-induced lysosomal lipolysis upregulates histone H3.3 variant HIS-71 in intestinal cells via SKN-1 transcription factor.
- HIS-71 protein is transported from the intestine to germline oocytes via vitellogenin lipoproteins and the RME-2 receptor.
- Germline-specific H3K79 methyltransferase DOT-1.3 writes heritable H3K79me2 marks that propagate longevity across up to three generations.
- Overexpressing HIS-71 or DOT-1.3 alone in the germline is sufficient to extend lifespan across multiple generations.
Methodology
The study used C. elegans with tissue-specific transgenic overexpression, CRISPR-tagged endogenous proteins, and auxin-inducible degron protein degradation to dissect intestinal and germline contributions. Genome-wide ChIP-seq for multiple H3 methylation marks combined with RNA-seq identified epigenetic and transcriptional targets of lysosomal signaling. Transgenerational lifespan assays tracked longevity phenotypes up to four generations after removing the longevity-inducing ancestor.
Study Limitations
All findings are in C. elegans; mammalian conservation of the intestine-to-germline histone transport mechanism has not been demonstrated. The specific downstream gene expression programs driven by heritable H3K79me2 marks that mediate longevity were not fully identified. The study does not address whether the transgenerational effect is fully epigenetic or partially influenced by residual molecular factors inherited alongside histones.
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