February 6, 2008 | David F. Coppedge

Of All the Nerve: Functional Intron Discovered

An intron vital to the production of nerve cells has been discovered, reported Science Daily.  It acts as a “gatekeeper” to guide the messenger RNA for local control of gene expression in dendrites, the spindly arms of neurons.  The discovery was made by a research team at University of Pennsylvania School of Medicine.
    “The group surmises that the intron may control how many mRNAs are brought to the dendrite and translated into functional channel proteins,” the article says.  “The correct number of channels is just as important for electrical impulses as having a properly formed channel.
    Introns had long been assumed to be junk that the spliceosome cuts out of a transcribed messenger RNA.  The team found that knocking out the intron in this case, however, produced abnormal electrical properties in the nerve cells.  “This is the first evidence that an intron-containing RNA outside of the nucleus serves a critical cellular function,” said James Eberwine, senior author.
    Eberwine also added this comment: “Just because the intron is not in the final channel protein doesn’t mean that it doesn’t have an important purpose.”  In fact, the article says, they may have hit on a general mechanism for the regulation of RNAs.
    The treasures being found in “junk DNA” are good for business.  A company named Rosetta Genomics is hoping to cash in on the new discoveries to be made about micro-RNAs (miRNA).  Noting the steep rise in articles about treasure in junk DNA, reporter Ohad Hammer said, “Rosetta Genomics’ impressive pipeline, unparalleled discovery capabilities and intellectual property make it one of the most exciting biotech companies out there.”
    Those interested in more technical detail about introns and alternative splicing may find revealing new ideas about intron function in a paper published by a team of European scientists in Nature last month,1 “Translational control of intron splicing in eukaryotes.”  The abstract says, for example, “In multicellular eukaryotes, long introns are recognized through exon definition and most genes produce multiple mRNA variants through alternative splicing.”


1.  Jaillon et al, Translational control of intron splicing in eukaryotes,” Nature 451, 359-362 (17 January 2008) | doi:10.1038/nature06495.

They also serve who only stand and wait –John Milton.  These introns should not have been assumed to be junk, even if all they did was stand and wait.  Apparently they are doing much more than that.
    For background on the mystery of introns, see 05/27/2004 commentary, 09/03/2002 and 09/12/2002 entries and 09/12/2003 update.

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Categories: Genetics

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