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Re: Article: Methylating memories; the meme <--> gene link?

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  • Dr. Angell O. de la Sierra, Esq.
    ... quotes: Epigenetic modification of DNA is important in memory formation. Might this methylation modification represent the mechanism whereby memes gain
    Message 1 of 2 , Apr 1 4:51 PM
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      --- In MindBrain@yahoogroups.com, "Robert Karl Stonjek" <stonjek@...>
      quotes: "Epigenetic modification of DNA is important in memory
      formation."

      Might this methylation modification represent the mechanism whereby
      'memes' gain access to heritable fragments of DNA in germinal cells?
      Likewise, the Jacques/Monod yesteryear success in adapting bacteria to
      metabolize lactose (DNA derepression?) may now be labeled a
      de-methylation activation of gene responsible for lactose dehydrogenases
      coding? Interesting...... Dr.d








      not remember anything before the age of three. However, the brain seems
      to use mechanisms important in fetal development for lifelong learning
      and memory. During mitosis, epigenetic modifications, including DNA
      methylation, enable parent cells to pass phenotypes on to daughter
      cells. Now Miller and Sweatt report that methylation of DNA is important
      for memory formation in a recent article in Neuron.
      >
      > The addition of methyl groups to DNA suppresses gene expression by
      physically blocking transcription factor binding to DNA. DNA
      methyltransferase adds methyl groups to cytosine-guanine nucleotide
      pairs.
      >
      > The authors found increased expression of DNA methyltransferases
      during memory formation in the adult hippocampus. In contextual fear
      conditioning, animals learn to associate a shock with an environment.
      When they are returned to the shock environment, rats freeze with fear.
      Thirty minutes after contextual fear training, rats showed increased
      hippocampal expression of mRNA encoding the DNA methyltransferases (3a
      and 3b) that are important during development.
      >
      > Inhibition of DNA methyltransferases blocked memory formation. The
      authors infused DNA methyltransferase inhibitors or vehicle into the
      hippocampus following training and tested freezing in the shock
      environment 24 hours later. Rats treated with inhibitors showed reduced
      freezing relative to rats treated with vehicle. DNA methyltransferase
      inhibitors did not permanently impair memory formation. After testing,
      the authors retrained the rats. Twenty-four hours later, rats that had
      previously been treated with DNA methyltransferase inhibitors showed
      freezing comparable to vehicle-treated rats tested 24 hours after
      training.
      >
      > Protein phosphatase 1 (PP1) suppresses memory formation, and PP1
      inhibition increases long-term potentiation and associative learning.
      The authors used methylation-specific real-time PCR to quantify
      methylated and unmethylated PP1 after contextual fear conditioning. One
      hour after training, rats trained to associate a shock with an
      environment showed increased methylation of hippocampal PP1 relative to
      rats exposed only to the shock or the shock environment and reduced
      expression of PP1 mRNA relative to rats exposed only to the shock
      environment. Relative to vehicle-treated controls, rats treated with DNA
      methyltransferase inhibitors immediately after training showed less
      methylated PP1, more unmethylated PP1 and greater expression of PP1
      mRNA. Together, these data suggest that DNA methylation suppresses PP1
      expression during associative learning.
      >
      > Associative learning decreased methylation of reelin, another gene
      that is important in memory formation. One hour after training, rats
      trained to associate shock with an environment showed less methylated
      and more unmethylated reelin DNA relative to rats exposed only to shock
      or the shock environment and increased reelin mRNA expression relative
      to rats exposed only to the shock environment.
      >
      > DNA methyltransferase inhibition did not alter PP1 mRNA expression in
      untrained rats, suggesting that methylation of PP1 in the adult
      hippocampus is specific to memory formation. Expression of both PP1 and
      reelin returned to baseline levels within 24 hours of contextual fear
      conditioning training, suggesting that regulation of DNA methylation is
      both rapid and dynamic.
      >
      > Rett syndrome is associated with mutations in methyl-CpG-binding
      protein 2 (MeCP2), which binds to methylated DNA, and schizophrenia is
      associated with hypermethylation of reelin, suggesting that disruption
      of DNA methylation can result in neurological disorders that impair
      memory and cognition.
      >
      > Author: Debra Speert
      >
      > 1.. Miller, C. A. and Sweatt, J. D. Covalent modification of DNA
      regulates memory formation. Neuron 53, 857-870 (2007).
      > Source: Nature
      > http://www.brainatlas.org/aba/2007/070329/full/aba1729.shtml
      >
      > Posted by
      > Robert Karl Stonjek
      >
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