. Human induced pluripotent stem cells free of vector and transgene sequences. Science. 2009 May 8;324(5928):797-801. PubMed.


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  1. The paper by Trouche and colleagues suggests that the functional relevance of newly integrated neurons in the granule layer of the dentate gyrus is determined by the context of the learned task, or in other words, is stimulus-dependent. These observations suggest that newly formed neurons can be “programmed” during their maturation, by a given learning experience, to strengthen memory networks supporting the learned task. For an optimal “programming” effect of new neurons, the learning experience should take place during the “receptive” period of these newly born cells, presumably during the first one to two weeks of their lives.

    In addition, this study raises the intriguing possibility that a repetitive presentation of a previously learned task or event should lead to the recruitment of a higher number of new neurons. Repetitive learning underlies other forms of brain plasticity. Motor practice, skill acquisition, and repetitive training (e.g., piano players, readers) are examples of use-dependent plasticity. They are accompanied by corresponding increases in excitability of relevant cortical areas and enlargement of cortical maps.

    View all comments by Orly Lazarov
  2. I think it is a great advance in reprogramming technology. Although
    they still need to check that there is no episomal vector left in the
    iPS subclones, use of the episomal vector removed a process of genetic
    manipulation, and passive removal of the vector seemed to be efficient.
    The reprogramming efficiency is still low, and it is not clear whether
    the technology can be applied to everybody, e.g., old people's cells, but
    it could be improved by combined use of small molecules and/or our 2A
    peptide one vector system.

    View all comments by Keisuke Kaji
  3. I am really excited to see that more and more means of generating genetically unaltered iPS cell lines are going to be available. They all have their own pros and cons and will go through further improvement in the near future. At this point, there is no way to see which one is going to be superior over the others. Most likely there will be no single winner of this “race." The choice of method will depend on further improvements, availability, ease, the question being addressed, and downstream applications.

    View all comments by Andras Nagy

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