Researchers use DNA origami to generate tiny mechanical devices that deliver a drug that cuts off the blood supply to tumors in mice.
Faux stem cells; X chromosome involved in sperm production; rewarding peer review; clues to flatworm regeneration; an ethereal glow signals death
July 26, 2013|
WIKIMEDIA, NISSIM BENVENISTYA new study attempting to nail down the existence of very small embryonic-like stem cells (VSELs)—seemingly pluripotent cells first reported in mouse bone marrow in 2005, and later identified in human blood and bone marrow—finds convincing evidence that the cells are not real. Lead author Irving Weissman of Stanford University School of Medicine called reports of VSELs a “distraction,” drawing excitement as well as time and money away from the more established stem cell types.
Others agreed. “In a rapidly evolving field, exciting and provocative early stage findings can often be subject to over-interpretation,” said Martin Pera, chair of Stem Cell Sciences at the University of Melbourne in Australia, who was not involved in the study. “This work shows that it is absolutely critical for multiple laboratories to confirm rigorously the developmental potential of candidate stem cells, before a new finding is accepted as dogma, or forms the basis for science policy decisions.”
The discoverer of VSELs, Mariusz Ratajczak of the Developmental Biology Research Program at the University of Louisville, stands by his research, however, and suggests methodological issues may explain other researchers’ inability to isolate the cells. And, as he has since his initial discovery in 2005, he emphasized the potential of the cells in regenerative medicine. “Based on very encouraging data, we predict that these cells could become an alternative for induced pluripotent stem cells and [embryonic stem cells],” he said in an email to The Scientist.
FLICKR, COLM MCMULLANThe supposedly “female” chromosome may have a very male role after all: mediating male infertility and sperm production. The X is also much more rapidly evolving that previously believed, according to research published this week. The researchers came to these conclusions after re-sequencing the existing human X chromosome assembly and comparing it with the X of the mouse, which revealed that while certain regions were highly genetically similar, many others were not shared—a finding that challenged the long held dogma that X-linked genes vary little among mammals. “The big surprise is that the X chromosome in both humans and mice has been evolving towards a kind of male specialization,” senior author David Page, a geneticist at the Whitehead Institute at the Massachusetts Institute of Technology, told The Scientist. “This flies in the face of a deep-seated, even if not scientifically substantiated, view that the X chromosome is female leaning.”
WIKIMEDIA, AREYNReviewing manuscripts submitted to peer-review journals is a thankless job—but it shouldn’t be, argues David Cameron Duffy, an ecologist at University of Hawaii at Manoa, in an opinion on www.the-scientist.com. In fact, Duffy proposes a system that evaluates reviewers just like the ones the scientific community uses to evaluate researchers on the basis of their publication output or journals on their citation rates. “For authors, we have a measure of impact, such as the commonly used h-index, a reflection of publications and citations,” he writes. “For journals, we have impact factors. . . . I suggest something similar would be a more benevolent system for referee metrics.”
Specifically, he suggests that journals keep track of who’s doing the reviewing for them, and individual reviewers could be judged on the basis on the number of papers they’ve reviewed, scaled by the impact factor of the journal to which the papers were submitted. “Assigning a specific score to evaluate a scientist’s contribution as a manuscript reviewer should encourage scientists to improve their standings,” Duffy writes. “The result would be competition for opportunities to review rather than competition among editors for a limited number of able and willing reviewers.”
JAMES SIKESMany flatworms have impressive regeneration abilities, easily regrowing their heads, for example. But other flatworms have partially lost this ability. Now, three independent groups have shown that tweaking a single pathway can arm regeneration-deficient flatworms with the ability once again. In three different species of partially regenerative worms, manipulation of the Wnt/β-catenin signaling pathway—known for its role in body patterning in diverse animals—allowed the animals to regenerate heads. “[It’s] a striking result,” said Peter Reddien, a developmental biologist at the Massachusetts Institute of Technology’s Whitehead Institute who was not involved in the studies. “[The worms] have the ingredients, but something is wrong with the ability to execute that type of regeneration program.”
CASSANDRA COBURNAs a nematode nears the end of its life, it experiences a wave of cell death—and emits a corresponding wave of blue light. And according to new research, the fluorescence results from an unexpected source: a substance called anthranilate in the worms’ intestinal cells. Anthranilate does not fluoresce when contained in the gut granules of the intestines, the researchers found, but as the cells die, and the organelles’ membranes deteriorate, the substance is released into the more alkaline cytoplasm—and the result is a pretty blue glow. In the minutes and hours preceding death, “you get this explosion of fluorescence—this extraordinary wave of fluorescence that goes through the worm,” said coauthor David Gems of University College London. When the scientists inhibited pathways involved in necrosis, the death-related burst of fluorescence failed to materialize.
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