Science  05 Oct 2012:
Vol. 338, Issue 6103, pp. 23

You are currently viewing the .

View Full Text

Log in to view the full text

Log in through your institution

Log in through your institution

  1. Obesity Hormone in Fruit Flies

    When it comes to mealtime, fruit flies are more like people than we thought. The insects, researchers have found, churn out the hormone leptin—the same hormone that helps control appetite and metabolism in humans. Leptin has long fascinated scientists, who study it to sort out the molecular underpinnings of obesity. But until now, they thought that only vertebrates produced it. This new find could make it easier to uncover leptin's secrets.


    Akhila Rajan, a postdoctoral fellow at Harvard Medical School in Boston, and her adviser, Norbert Perrimon, made the discovery after engineering flies that lacked a nutrient-sensing protein called Upd2. Flies without Upd2 look metabolically as if they're famished. But when Rajan inserted the human leptin gene into her flies, they didn't have that problem. The researchers concluded in a study published last week in Cell that Upd2 is the “functional homolog” of leptin, meaning the protein in flies acts very much as leptin does in people. Because flies are relatively easy to study in the lab, the researchers hope their discovery will make it easier to study leptin's biology.

  2. Concrete Evidence for Water on Ancient Mars


    Billions of years ago, enough water flowed into Gale crater fast enough to carry gravel to the middle of the crater floor—where the Curiosity rover has found and imaged it, the NASA mission's team reported in a press conference on 27 September. The broken face of a 15-centimeter-thick layer of rock sports bits of stone worn into pebbly roundness as they tumbled down from the nearby crater rim in a torrent of water. Previous Spirit and Opportunity rover investigations and orbital imaging have found evidence of salty ground water, evanescent puddles of brine, and flowing rivers on ancient Mars. But properties of the newly discovered rock, such as the size range of the gravel, will let researchers infer a great deal more about ancient water on Mars. Unfortunately, gravel laid down in torrential flows is about the worst sort of deposit to search for traces of ancient life. As demonstrated on Earth, the organic remains of long-ago life are far better preserved in the muddy deposits of quiescent lake bottoms.

  3. Oocytes Created in a Dish Produce Normal Mice

    A Kyoto University team led by stem cell biologist Mitinori Saitou has produced normal mouse pups using oocytes, or immature egg cells, created in vitro from embryonic stem cells and induced pluripotent stem cells (ES cells and iPS cells). The achievement is a first for mammals.

    The researchers cultured mouse ES and iPS cells in protein cocktails to produce primordial germ cell-like cells. To get oocytes, they mixed these cells with fetal ovarian cells, forming reconstituted ovaries that they grafted onto natural ovaries in female mice. Four weeks later, the primordial germ cell-like cells had developed into oocytes. After in vitro fertilization, the researchers implanted the resulting embryos into surrogate mothers, producing normal mouse pups, the team reported online on 4 October in Science.

    “It is remarkable that one can produce oocytes capable of sustaining complete development starting with embryonic stem cells,” says developmental biologist Davor Solter of Singapore's Institute of Medical Biology who was not involved with the research. Saitou says that with more work, the team may be able to eliminate the grafting step, generating viable oocytes completely in vitro. In addition to shedding light on early developmental processes, the technique could lead to new human fertility treatments if technical challenges and ethical issues can be resolved, he says.