Science  23 Mar 2012:
Vol. 335, Issue 6075, pp. 1423

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  1. Immune Cells Alleviate Symptoms Of Rett Syndrome in Mice

    One out of about every 10,000 girls is born with Rett syndrome, a genetic condition that stunts growth, causes autism-like behavior, and impairs sleeping, breathing, and movement. A new study with mice suggests that microglia, a type of immune cell in the brain, play a role in the disorder and may even be a promising therapeutic target.

    Neuroimmunologist Jonathan Kipnis of the University of Virginia in Charlottesville and colleagues transplanted bone marrow from normal mice into mice with a gene mutation like the one that causes Rett syndrome, thereby giving the mutants a new set of immune cells. Untreated mice got sick and died within a few weeks of birth, but the treated mice had far fewer symptoms and longer lifespans, the team reports in Nature. The benefit seems to come from repopulating the brain with genetically normal microglia, whose job it is to clean up cellular debris. Any clinical trials are a long way off, but Kipnis says the findings raise the possibility of using bone marrow transplants to treat girls with Rett syndrome.

  2. More, More Iron for Mercury

    The solar system's Iron Planet is living up to its name. A team on the MESSENGER mission orbiting Mercury reports online in this week's issue of Science the discovery of more iron than previously thought deep in the planet's interior.

    Finding unseen iron required exquisitely sensitive measurements of the motions of both the MESSENGER spacecraft and Mercury. Using measurements of the Doppler frequency shift in the spacecraft's radio signal, the team gauged the variations of gravity across Mercury. Those, in turn, depend on where mass is concentrated in the interior. The internal mass distribution also affects the tilt of Mercury's axis of rotation and the speed of rotation, which were measured using Earth-based radar.

    Iron inside.

    An iron sulfide layer may extend Mercury's iron core.


    The combined gravity and radar data point to plenty of iron in Mercury. Much of it is likely in the liquid core, now seen to extend 2030 kilometers from the center of Mercury, or 83% of the planetary radius. And the team sees another, unexpected place iron may be stored: a layer of iron sulfide that could have frozen out of the liquid core. That electrically conductive layer might explain Mercury's oddly weak magnetic field.