27.1 Highlights 373 MH

research highlights Cancer Self-assembly Telomeres on a Pots of soap short leash Langmuir 21, 516–519 (2005) Cancer Cell 7, 25–37 (2005) Structures that look like earthenware spun on a Treatments that throw a double punch at wheel emerge spontaneously from a solution of chromosome ends could kill off cancer cells, a common cosmetics surfactant, Janhavi S. Raut Hiroyuki Seimiya et al. suggest. DNA et al. report. This ‘micro-pottery’ is built from sequences known as telomeres, typically aggregates of the surfactant sodium myristate, found at chromosome ends, help normal which self-assemble when a concentrated solution cells keep tabs on how many times they have is cooled to room temperature. divided. Chromosomes must be replicated For fast cooling rates, the fibres simply tangle before cells can divide, but the very tips of into a gel-like mat. If cooling is slower than 2 ᑻC telomeres cannot be copied, so, with each per minute, the fibres begin to curl into rings; at division, these sequences get shorter and 1 ᑻC per minute they form bundles like thread shorter. Eventually, they become so wound on a bobbin. Air bubbles in the cooling truncated that the DNA cannot be properly solution become covered in bundles in which the replicated, and the cell stops dividing. fibres are spooled into appealing shapes (pictured), Cancer cells, however, contain an about 10–20 Ȗm across. activated enzyme called telomerase, which Raut et al. think that the initial bending of the prevents telomeres from shortening and fibres into rings, which act as seeds for ‘spinning’ leads to uncontrolled proliferation. So the micro-pots, is triggered by pressure gradients researchers have been developing treatments at the air–water interface of the bubbles. These that inhibit this enzyme. But these therapies gradients arise from differences in surfactant micro-pots represent a third level of structural do not always succeed, and can produce concentration across the surface, leading to hierarchy in the surfactant assemblies, which drug resistance. variations in surface tension that drive liquid form sheets that then gather in layers to create the To develop a better treatment option, flow: the so-called Marangoni effect. The ribbon-like fibres. Philip Ball Seimiya et al. investigated what happened when they inhibited both telomerase and another enzyme, tankyrase 1, that helps it The discovery raises the possibility that planets themselves. Further study will focus gain access to telomeres. This enhanced the drugs that block GSK-3ȋ could be used on the size and composition of the particles shortening of these chromosomal ends, and to promote axonal growth and so enhance in the disk. Mark Peplow accelerated cancer-cell death. The authors the repair of neuronal injuries, although suggest that tankyrase 1 inhibitors might the researchers have not yet shown that Zoology significantly boost the efficacy of telomere- the new axons would work normally Estimating the unknown targeted therapies. Roxanne Khamsi in animals. Helen Pearson Proc. R. Soc. Lond. B doi:10.1098/rspb.2004.2955 Developmental biology Astronomy Andrew R. Solow and Woollcott K. Smith Switch of fate Dusty dwarfs have taken a fresh look at estimating the number of species in a particular category Cell 120, 123–135; 137–149 (2005) Astrophys. J. (in the press) of animals, including those that are yet to Neurons produce two very distinct types Brown dwarfs are the failed stars of the be discovered. of projection: a single axon, which passes cosmos. With insufficient mass to fuse A traditional approach is to take the signals on to neighbouring cells, and hydrogen atoms, they glow weakly by cumulative historical record of discoveries numerous dendrites, which receive signals burning deuterium. Astronomers are still of species, and extrapolate into the future. from axons. Two groups have now found unsure whether the smallest brown dwarfs Solow and Smith propose a statistical model that an enzyme called glycogen synthase form like their larger cousins — by accreting for the ‘discovery process’,which can be fitted kinase-3ȋ (GSK-3ȋ) helps to determine matter from a swirling disk of dust particles. to the data using the principle of maximum what a projection becomes. K. L. Luhman and colleagues have found likelihood, based in probability theory. Hui Jiang et al. and Takeshi Yoshimura the smallest and coolest brown dwarf to Central elements factored into the procedure et al. showed that GSK-3ȋ blocks the date that is surrounded by a dusty disk. The are the animals’ visibility, and a function formation of axons. When they boosted dwarf, called OTS 44, is about 15 times the to account for changes over time in the skill the activity of GSK-3ȋ in cultured neurons, mass of Jupiter, right at the lower mass limit and effort applied in sighting new species. the cells often lacked axons completely. necessary for deuterium burning. The The authors test their model against a Conversely, when GSK-3ȋ was inhibited, the observation of a disk around such a small previously published record of the dates cells sprouted several axons — or converted star implies that the accretion mechanism when large marine animals (defined as existing dendrites into axons. works for even the smallest stars. 2 metres or more in length) were discovered, The groups went on to identify molecules The researchers used infrared starting in 1828 and ending in 1996. That working upstream and downstream of measurements from the Spitzer Space record comprises 117 species, with a further GSK-3ȋ. They showed that GSK-3ȋ is Telescope to identify the disk around the 100 having been identified before 1828. tagged with phosphate groups and thereby dwarf star. It lies in the Chamaeleon I cloud The upshot of the calculations, activated by the enzyme Akt. GSK-3ȋ then complex, a nearby star-forming region say Solow and Smith, is that around itself phosphorylates and inhibits a molecule about 554 light years from Earth. 10 large marine animals remain to be called CRMP-2, which normally promotes The finding raises the possibility that discovered, and probably 16 at most. the assembly of the neuron’s internal planets could form from dust around brown The most likely candidates are fish and ‘skeleton’ and hence axon growth. dwarfs that have barely more mass than cephalopods. Tim Lincoln NATURE | VOL 433 | 27 JANUARY 2005 | www.nature.com/nature 373 © 2005 Nature Publishing Group.

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