Cortical DNA methylation maintains remote memory

Journal name:
Nature Neuroscience
Volume:
13,
Pages:
664–666
Year published:
DOI:
doi:10.1038/nn.2560
Received
Accepted
Published online

A behavioral memory's lifetime represents multiple molecular lifetimes, suggesting the necessity for a self-perpetuating signal. One candidate is DNA methylation, a transcriptional repression mechanism that maintains cellular memory throughout development. We found that persistent, gene-specific cortical hypermethylation was induced in rats by a single, hippocampus-dependent associative learning experience and pharmacologic inhibition of methylation 1 month after learning disrupted remote memory. We propose that the adult brain utilizes DNA methylation to preserve long-lasting memories.

At a glance

Figures

  1. Learning induces persistent DNA methylation of CaN in the prefrontal cortex.
    Figure 1: Learning induces persistent DNA methylation of CaN in the prefrontal cortex.

    (a) CaN CpG island analyzed and primer location. CaN was hypermethylated in context and shock rats at 1 and 7 d (no retrieval test; 1 h, F3,18 = 0.27; 1 d, F3,19 = 5.73; 7 d, F3,25 = 33.52; post hoc test, *P ≤ 0.05). CaN's hypermethylation was significantly greater at 1 and 7 d (F2,20 = 13.96, #P ≤ 0.01). See Supplementary Table 1 for n values. TSS, transcription start site. (b) Amplicon analyzed by bisulfite sequencing and subcloning at 7 d. Charts depict the number of alleles with 0, 1, 2 or 3 methylated CpGs in the amplicon. (c) Single allele cytosine methylation for the 59 CpGs located in the amplicon at 7 d (n = 4 per group). See Supplementary Table 2 for primer sequences. Error bars indicate s.e.m.

  2. Cortical DNA methylation persists for at least 30 d.
    Figure 2: Cortical DNA methylation persists for at least 30 d.

    (a) CaN was still hypermethylated 30 d after training (F3,19 = 4.77; *P ≤ 0.05). (b) CaN transcript was decreased in context plus shock at 30 d (t5 = −8.36, **P ≤ 0.001, F2,15 = 12.72). (c) CaN protein levels were decreased in context plus shock 2 h after retrieval test (F3,30 = 24.31). See Supplementary Table 3 for n values. Error bars indicate s.e.m.

  3. Cortical DNA methylation is required for remote memory.
    Figure 3: Cortical DNA methylation is required for remote memory.

    (a) Intra-ACC infusions of 5-azadeoxycytidine (5-aza, n = 14 and 13, F1,26 = 11.48), zebularine (zeb, n = 7 and 7, F1,13 = 21.07) or RG108 (n = 10 and 10, F1,19 = 5.17) 30 d after training disrupted remote fear memory (*P ≤ 0.05). (b) DNMT inhibitors (DNMTi) interfered with context plus shock (CS)-induced CaN methylation (n = 6 and 6, F1,11 = 8.96) and normalized CaN transcript levels (t8 = 8.34, **P ≤ 0.001). (c) Intra-ACC infusions of DNMT inhibitors 1 d after training had no effect on fear memory (n = 7 and 8, F1,14 = 0.81, P > 0.05). The same rats also expressed normal fear memory 30 d later (F1,12 = 0.26, P > 0.05). Experiment was repeated in absence of a test at 2 d to confirm lack of damage to ACC. Again, infusions had no effect on fear memory (n = 7 and 8, F1,14 = 0.81, P > 0.05). Error bars indicate s.e.m.

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Affiliations

  1. Department of Neurobiology and Evelyn F. McKnight Brain Institute, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, USA.

    • Courtney A Miller,
    • Cristin F Gavin,
    • Jason A White,
    • R Ryley Parrish,
    • Avinash Honasoge,
    • Christopher R Yancey,
    • Ivonne M Rivera,
    • María D Rubio,
    • Gavin Rumbaugh &
    • J David Sweatt
  2. Present address: Department of Metabolism and Aging, The Scripps Institute, Jupiter, Florida, USA (C.A.M.), Department of Neuroscience, The Scripps Institute, Jupiter, Florida, USA (C.A.M., C.F.G. and G.R.).

    • Courtney A Miller,
    • Cristin F Gavin &
    • Gavin Rumbaugh

Contributions

C.A.M. and J.D.S. conceived of the project. C.A.M., G.R. and J.D.S. designed the experiments. G.R. contributed to assay development. C.A.M., C.F.G., J.A.W., R.R.P., I.M.R., A.H., M.D.R. and C.R.Y. performed the experiments. C.A.M. wrote the manuscript. G.R. and J.D.S. edited the manuscript.

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The authors declare no competing financial interests.

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