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Brain growth depends on shapely neurons
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Jochen Tack/Alamy
YOU could call it an invisible mugshot. Police may one day be able to reconstruct the shape of a suspect’s face from their DNA alone, thanks to the identification of five genes that contribute to facial shape. DNA tests for predicting eye, hair and skin colour are currently available or under development, so identifying genes linked with facial features could help to create a more detailed identikit picture from someone’s DNA. Manfred Kayser from the Erasmus University Medical Center in Rotterdam, the Netherlands, and his colleagues analysed DNA from 10,000 white Europeans. They examined 17 facial “landmarks” using three-dimensional MRI scans of their heads and photographs of their faces. The team identified five genes associated with facial features – but they caution that the genes only have small effects. For example, a gene called TP63 can narrow the gap between the centres of each eye socket by a maximum of just 9 millimetres. “It’s a start,” says Kayser. “But we are far away from predicting what someone’s face looks like.” Other genes influenced the length of the nose, the distance from the eyes to the bridge of the nose, and the width between cheekbones (PLoS Genetics, doi.org/jcv).
It’s slow with the flow for world’s tiniest trickle FILLING a cup from this tap would take 40,000 years, but luckily its raison d’être has nothing to do with quenching thirst. The trickle in question flows along a silicon chip and is the slowest ever recorded. Its detection should speed up the creation of the first fully electronic lab-on-a-chip. Such devices are too small for fluids flowing through them to be visible, but measuring the flow rate of an extremely small sample of blood, say, can help detect traces of disease. It is possible to do this using lasers
and fluorescent markers, but to interpret the results, the optical signals must be converted into electrical ones, which is cumbersome. Klaus Mathwig of the University of Twente in Enschede, the Netherlands, and his colleagues wondered whether they could detect tiny flow rates using only electronics. They carved a tunnel, 100 micrometres long, 5 micrometres wide and just 130 nanometres high, in a silicon chip and placed electrodes at each end. Then they pumped
through water spiked with electrochemically active molecules, which register a characteristic electrical signal as they flow past the electrodes. This allowed the researchers to measure the fluid’s flow rate (Physical Review Letters, doi.org/jcs). The slowest flow rate recorded was 10 picolitres per minute, a third as fast as the previous lowest flow of 30 picolitres per minute, which was measured optically. “This is the smallest flow reported,” confirms team member Serge Lemay. ibm research/zurich
Mugshot without a face, from DNA
Brain growth down to shapely cells THE human brain may be the most complex object in the universe, but its construction mostly depends on one thing: the shape of neurons. Different kinds of neuron are selective about which other neurons they connect to and where they attach. Specific signalling chemicals are thought to be vital in guiding this process. Henry Markram of the Swiss Federal Institute of Technology in Lausanne and colleagues built 3D computer models of the rat somatosensory cortex, each containing a random mix of cell types found in rat brains, but no signalling chemicals. Nevertheless, 74 per cent of the connections ended up in the correct place, merely by allowing the cells to develop into their normal shape (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1202128109). The results suggest that much of the brain could be mapped without incorporating signalling chemicals. This is good news for neuroscientists struggling to map the brain’s dizzying web of connections. “It would otherwise take decades to map each synapse in the brain,” says Markram.
First images of atomic bonds revealed SHARING more leads to tighter bonds, even in the world of molecules. The most detailed images yet made of the chemical bonds in a molecule show what large-scale models had long assumed: the more electrons that two atoms share, the shorter the bond between them. Bonds that are more electron-dense also appear brighter in the images. In molecules, atoms can share one or more of their outermost electrons in a covalent bond. How many electrons they share determines the bond’s strength, an important factor in predicting the molecule’s
geometry, stability and reactivity. Using a modified atomic force microscope, Leo Gross of IBM Research in Zurich, Switzerland, and colleagues captured bonds in three different carbon molecules, including the flat form of hexabenzocoronene pictured above (Science, doi.org/jcr). Bonds that are more electron-dense are shorter, although only by a few picometres, or trillionths of a metre. Such images could give a deeper understanding of chemical reactions, and may help researchers size up molecules for use as electrical components in tiny circuits.
22 September 2012 | NewScientist | 15
Jochen Tack/Alamy
YOU could call it an invisible mugshot. Police may one day be able to reconstruct the shape of a suspect’s face from their DNA alone, thanks to the identification of five genes that contribute to facial shape. DNA tests for predicting eye, hair and skin colour are currently available or under development, so identifying genes linked with facial features could help to create a more detailed identikit picture from someone’s DNA. Manfred Kayser from the Erasmus University Medical Center in Rotterdam, the Netherlands, and his colleagues analysed DNA from 10,000 white Europeans. They examined 17 facial “landmarks” using three-dimensional MRI scans of their heads and photographs of their faces. The team identified five genes associated with facial features – but they caution that the genes only have small effects. For example, a gene called TP63 can narrow the gap between the centres of each eye socket by a maximum of just 9 millimetres. “It’s a start,” says Kayser. “But we are far away from predicting what someone’s face looks like.” Other genes influenced the length of the nose, the distance from the eyes to the bridge of the nose, and the width between cheekbones (PLoS Genetics, doi.org/jcv).
It’s slow with the flow for world’s tiniest trickle FILLING a cup from this tap would take 40,000 years, but luckily its raison d’être has nothing to do with quenching thirst. The trickle in question flows along a silicon chip and is the slowest ever recorded. Its detection should speed up the creation of the first fully electronic lab-on-a-chip. Such devices are too small for fluids flowing through them to be visible, but measuring the flow rate of an extremely small sample of blood, say, can help detect traces of disease. It is possible to do this using lasers
and fluorescent markers, but to interpret the results, the optical signals must be converted into electrical ones, which is cumbersome. Klaus Mathwig of the University of Twente in Enschede, the Netherlands, and his colleagues wondered whether they could detect tiny flow rates using only electronics. They carved a tunnel, 100 micrometres long, 5 micrometres wide and just 130 nanometres high, in a silicon chip and placed electrodes at each end. Then they pumped
through water spiked with electrochemically active molecules, which register a characteristic electrical signal as they flow past the electrodes. This allowed the researchers to measure the fluid’s flow rate (Physical Review Letters, doi.org/jcs). The slowest flow rate recorded was 10 picolitres per minute, a third as fast as the previous lowest flow of 30 picolitres per minute, which was measured optically. “This is the smallest flow reported,” confirms team member Serge Lemay. ibm research/zurich
Mugshot without a face, from DNA
Brain growth down to shapely cells THE human brain may be the most complex object in the universe, but its construction mostly depends on one thing: the shape of neurons. Different kinds of neuron are selective about which other neurons they connect to and where they attach. Specific signalling chemicals are thought to be vital in guiding this process. Henry Markram of the Swiss Federal Institute of Technology in Lausanne and colleagues built 3D computer models of the rat somatosensory cortex, each containing a random mix of cell types found in rat brains, but no signalling chemicals. Nevertheless, 74 per cent of the connections ended up in the correct place, merely by allowing the cells to develop into their normal shape (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1202128109). The results suggest that much of the brain could be mapped without incorporating signalling chemicals. This is good news for neuroscientists struggling to map the brain’s dizzying web of connections. “It would otherwise take decades to map each synapse in the brain,” says Markram.
First images of atomic bonds revealed SHARING more leads to tighter bonds, even in the world of molecules. The most detailed images yet made of the chemical bonds in a molecule show what large-scale models had long assumed: the more electrons that two atoms share, the shorter the bond between them. Bonds that are more electron-dense also appear brighter in the images. In molecules, atoms can share one or more of their outermost electrons in a covalent bond. How many electrons they share determines the bond’s strength, an important factor in predicting the molecule’s
geometry, stability and reactivity. Using a modified atomic force microscope, Leo Gross of IBM Research in Zurich, Switzerland, and colleagues captured bonds in three different carbon molecules, including the flat form of hexabenzocoronene pictured above (Science, doi.org/jcr). Bonds that are more electron-dense are shorter, although only by a few picometres, or trillionths of a metre. Such images could give a deeper understanding of chemical reactions, and may help researchers size up molecules for use as electrical components in tiny circuits.
22 September 2012 | NewScientist | 15