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Re: News: Epigenetics: Neurons remember because they move genes in space

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  • clarence_sonny_williams
    Now this is really cool. We ve known for a while that chromatin movement (not just histone modifications) in the nucleus is another gene expression regulatory
    Message 1 of 2 , Mar 8, 2013
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      Now this is really cool. We've known for a while that chromatin
      movement (not just histone modifications) in the nucleus is another gene
      expression regulatory mechanism. When a genetic locus moves to the
      nuclear lamina, it is (usually) silenced. This mechanism is used quite
      often during development for neural fate decisions, but has been thought
      to be due to intrinsic chemical signals (including products of other
      genes). This research suggests that cues even external to other cells
      can "cause" this inter-nuclear movement.

      I cannot access the research for 6 months, but I'm trying to get it
      sooner. Anyone else on the group have immediate access? I sure would
      like a copy sent to clarencew@...

      --- In evolutionary-psychology@yahoogroups.com, "Robert Karl Stonjek"
      <stonjek@...> wrote:
      > Epigenetics: Neurons remember because they move genes in space
      > March 7th, 2013 in Neuroscience
      > How do neurons store information about past events? In the Nencki
      Institute of Experimental Biology of the Polish Academy of Sciences in
      Warsaw, a mechanism unknown previously of memory traces formation has
      been discovered. It appears that at least some events are remembered
      thanks to... geometry.
      > Neurons are the most important cells of the nervous system. Scientists
      from the Nencki Institute of Experimental Biology of the Polish Academy
      of Sciences in Warsaw have shown that during neuron stimulation
      permanent changes are observed with respect to genes' arrangement within
      the cell nucleus. This discovery, reported in the Journal of
      Neuroscience, one of the most prestigious journals in the field of
      neurobiology, is significant for developing a better understanding of
      the processes going on in the mind and disorders of the nervous system,
      especially the brain.
      > "While conducting experiments on rats after epileptic seizures we have
      observed that a gene may permanently move deeper into the neuron's cell
      nucleus. Since modification of the geometrical structure of the nucleus
      leads to changes in gene expression, this is how the neuron remembers,
      what happened", explains Prof. Grzegorz Wilczynski from the Laboratory
      of Molecular and Systemic Neuromorphology at the Nencki Institute.
      > Neurons connect with each another via synapses, forming extended
      networks. In order for the neuronal networks to retain traces of stimuli
      which caused activation, the shape and functioning of individual
      synapses has to change. If stimulus trace is to be permanent, changes
      are necessary in the expression of many genes located in the cell
      nucleus of individual neurons.
      > Genes are sections of the deoxyribonucleic acid (DNA) chain coding
      proteins. But the presence of a gene in the DNA does not mean that it is
      active. It has been known for the past several years that gene
      expression also depends on the environment within the cell. Chromatin
      which fills cells contains gene activating or supressing substances.
      > "This somewhat resembles interpersonal relations. When you attend a
      social gathering the importance of what you say will have a different
      impact depending on the environment. If the environment is favourable,
      your opinion will be seized on and reinforced and you will achieve
      social impact. If the environment is less friendly, your opinion will be
      silenced", explains Prof. Wilczynski.
      > In the case of neurons the epigenetic processes during which gene
      expression is decided by the environment, to date have been associated
      only with chemical reactions within the chromatin. Research done at the
      Nencki Institute has shown that in neurons we deal with yet another type
      of epigenetic effects: changes to the spatial structure of the cell's
      nucleus resulting in the formation of permanent memory traces. This is
      possible for two reasons. First of all because of the presence of the
      nuclear membrane: genes can attach or detach from it, which impacts
      their expression. The second reason is related to the specific structure
      of the cell nucleus.
      > The nucleus of a cell consists of many globules, called chromosome
      domains or territories. Each domain is filled by just one chromosome,
      which may slightly move within its territory. As a result of such
      movement at the meeting points of the neighbouring domains, fragments of
      the DNA chains containing the different genes can come in contact. This
      leads to silencing of a group of genes or to their expression: formation
      of a transcription factory. However, a slight movement of the DNA chain
      in any domain changes the situation: the silenced gene unit resumes
      activity or the factory stops functioning.
      > Changes to the spatial arrangement of genes within the cell nucleus
      have already been observed in certain types of cells, among other in
      epithelium cells. Research done at the Nencki Institute has shown that
      external stimuli may cause changes within neurons. Moreover scientists
      proved that such changes are permanent and create a distinct genetic
      memory trace within the neuronal structure - despite no changes recorded
      in the DNA chains themselves.
      > Neurons used in this study came from rats after epileptic seizure,
      which is a brain plasticity disorder. During the seizure the activated
      neurons are places of turbulent gene expression. Scientists from the
      Nencki Institute decided to investigate two genes, known as BDNF and
      TRKB. In collaboration with the group of Prof. Marek Switonski from the
      University of Life Sciences in Poznan, and with Prof. Marion Cremer from
      Munich, these genes' location within the DNA chains has been marked
      using a substance glowing after stimulation with laser light. Such
      preparations of neurons from control rats and neurons coming from rats
      after epileptic seizures were analysed under confocal microscope.
      > "Confocal microscope registers images only in the vicinity of its
      focal plane. Therefore each image represents a sort of flat, thin cross
      section through the preparation. To reconstruct from a set of many such
      slices the spatial structure of the cell nucleus and the arrangement of
      genes, we needed to design special software. This task turned out to be
      difficult since we were working at the limit of the microscope's
      resolving power", says Dr Blazej Ruszczycki from the Nencki Institute.
      > The software took one year to develop. It was used to study more than
      5000 cell nuclei to determine the location of both genes of interest
      with relation to the centres of the nuclei and the nuclear membrane. For
      the BDNF gene, a change has been observed in its location of a few
      hundred nanometres (one billionth part of a metre); in the control
      animals this gene was present near the nuclear membrane or on it in 50%
      of the nuclei, while in animals after seizures this value dropped to
      approximately 25%.
      > "A double drop is a great change in biology. Moreover, we have
      observed that it remains visible for up to several weeks. The conclusion
      is therefore clear: past events are remembered by neurons also thanks to
      changes within the architecture of their cell nuclei", observes Prof.
      > Provided by Nencki Institute of Experimental Biology
      > "Epigenetics: Neurons remember because they move genes in space."
      March 7th, 2013.
      > Posted by
      > Robert Karl Stonjek
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