Developmental Biology: Secrets of the heart
Cell doi:10.1016/j.cell.2006.10.029 and 10.1016/j.cell.2006.10.028 (2006)
The heart's three major muscles can all grow from a single cell type, researchers have shown. The finding will help research into regenerative heart therapies.
Previously it was thought that each of the heart's muscle types came from distinct source cells. But, using genetic mapping techniques, Kenneth Chien of the Harvard Stem Cell Research Institute in Boston, Massachusetts, and his team identified a cardiac progenitor cell that can differentiate into cardiac, endothelial or smooth-muscle cells. These cells may be the parent of a second cell type — identified by Stuart Orkin of the Howard Hughes Medical Institute, Boston, and his colleagues in a separate paper — that differentiates into two of the heart muscle types.
Cancer Biology: Orient distress
J. Cell Biol. 175, 547–554 (2006)
Many of the cells in our body use tiny hair-like antennae called monocilia as sensors. Now a team of researchers has shown how these monocilia go wrong in an inherited cancer syndrome called von Hippel–Lindau disease.
Thomas Benzing of the University Hospital Freiburg, Germany, and his colleagues examined how a faulty protein, pVHL, which underlies the disease, knocks out the formation of monocilia in kidney cells. The loss of these cilia contributes to the development of kidney cancer.
They found that pVHL localizes to the monocilia. There, it both interacts with other proteins involved in the cilia's formation and helps to orient microtubules, which form the scaffolding needed to build the protrusions.
Biomaterials: Copper-tinted roots
Biochemistry 45, 14223–14231 (2006)
Marine mussels may have copper atoms to thank for their tenacious grip, say researchers at the University of California, Santa Barbara.
Mussels take hold of a surface by laying down a sticky plaque and then planting 'feet' into this layer. Hua Zhao and J. Herbert Waite studied the chemical structure of the plaque matrix protein mcfp-4 produced by the California mussel (Mytilus californianus), noting that it contains a motif rich in the amino acid histidine that is repeated about 36 times. Such units can bind copper atoms.
The researchers suggest that similar copper-binding units might exist in the mussel's 'foot' threads, creating multiple anchor points that bind its foot to the plaque.
Genetics: Blue eyes or brown?
Am. J. Hum. Genet. (in the press)
Whether you have blue eyes or brown depends largely on three 'letters' in your genetic code, buried within a gene on your fifteenth chromosome. So conclude Richard Sturm of the University of Queensland in Brisbane, Australia, and his colleagues.
The researchers had previously shown that a particular region of the OCA2 gene could explain around three-quarters of the variation in human eye colour. They have now zoomed into this region, using data from 3,839 twins and their family members. They found three single-letter changes (known as single nucleotide polymorphisms, or SNPs) that are strongly associated with having blue eyes. The next challenge is to decipher the molecular mechanisms that translate the genetic differences into differences in iris pigment.
Nanotechnology: Ultimate strength
Nano Lett. doi:10.1021/nl0619397 (2006)
Semiconducting nanowires have displayed their maximum theoretical strength, report John Boland of Trinity College Dublin, Ireland, and his colleagues.
The germanium nanowires had been grown by a 'supercritical fluid–liquid–solid mechanism'. The team used the tip of an atomic force microscope to bend tethered wires, which snapped without showing any substantial plastic deformation. This suggests that defects in the wires' crystal structure, which would weaken the material, played no role in their response to stress. Indeed, the wires' breaking point was close to the predicted ultimate strength for germanium nanowires; many other semiconducting nanowires snap at just 15% of their theoretical limit.
The wires' elastic resilience could be useful in applications such as electromechanical oscillators, the researchers say.
Cancer biology: Attractive prospect
Nature Cell Biol. doi:10.1038/ncb1507 (2006)
Researchers in Japan have discovered a mechanism whereby cancers produce long-distance signals that prepare the ground for a deadly tumour invasion of the lungs. They have also shown how these signals can be interrupted.
Yoshiro Maru of the Tokyo Women's Medical University and his colleagues found that primary tumours in mice secrete factors that increase the expression in the lungs of two chemoattractants. These proteins encourage the tumour cells to migrate into lung tissue.
Antibodies that bind the chemoattractants slashed the level of lung metastases in tumour-bearing mice by more than 80%. The researchers suggest that the chemoattractants, or the circuit of signals that induces them, provide a new clinical target for the prevention of cancer metastasis.
Genetics: Forced apart
Science 314, 1292–1295 (2006)
Fruitflies have provided the first example of a genetic mechanism that helps to drive a wedge between diverging species.
Hybrids of two different species are often born dead or sterile, enforcing the species' split. Their reduced viability is thought to result from interactions between gene pairs, called Dobzhansky–Muller genes, that have functionally diverged in the two species.
Daniel Barbash and his colleagues at Cornell University in Ithaca, New York, report the first known pair of Dobzhansky–Muller genes in the related fruitflies Drosophila simulans and D. melanogaster. They show that interactions between the protein products of the two genes Lethal hybrid rescue and Hybrid male rescue kill hybrid flies. As these proteins are known to bind to chromosomes, the researchers suspect that the lethal effect is due to changes in chromosome structure or shape.
Nanotechnology: Grown from seed
J. Am. Chem. Soc. doi:10.1021/ja065767r (2006)
Just as gardeners can sow seeds to grow flowers of a particular colour, so chemists may soon be able to buy packets of seeds for growing specific varieties of carbon nanotube.
Nanotubes come in different widths and can vary in the amount of twist in their carbon walls. These characteristics determine the tube's properties — in particular, whether it is metallic or semiconducting. Researchers may want nanotubes of one type, but current synthesis methods give a mixture.
To solve this problem, James Tour and his co-workers at Rice University in Houston, Texas, divided a nanotube into short segments that can act as 'seeds' for growing identical tubes. They attached iron to the end of each segment, as this catalyses the growth of the seed when it is fed with a carbon-rich vapour. Cuttings can be taken from the resulting nanotube, from which further tubes can be grown if needed.
Planetary Science: Caught in the spokes
Geophys. Res. Lett. 33, L21202 (2006)
The mysterious and transient 'spokes' that cross Saturn's rings (pictured) might be caused by thunderstorms in the planet's atmosphere, researchers suggest.
Geraint Jones of the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, and his colleagues propose that electron beams discharged by thunder clouds are funnelled along the planet's magnetic-field lines and into the rings, where they blast out streams of dust.
Others have suggested that the dust streamers are created by meteorites ploughing through the rings, but Jones and his team contend that their theory can better explain why the spokes intensify over an hour or two. NASA's Cassini spacecraft has detected electron beams in orbit around Saturn, but there is as yet no direct evidence linking such beams either to thunderstorms or to spokes.
Science 314, 1298–1301 (2006)
Crop researchers have discovered a gene in wild wheat that, when bred into cultivated varieties, boosts the grains' nutritional value.
Varieties of wheat (pictured) cultivated for making pasta and bread account for around 20% of all calories consumed worldwide. But these strains have a mutation that reduces their protein, zinc and iron content, report researchers led by Jorge Dubcovsky of the University of California, Davis.
The team identified the mutated gene as NAM-B1, which controls the redistribution of nutrients to the grains when the leaves die off. They also found that wild strains of wheat have an intact version of this gene, which can be crossed into domesticated strains to increase levels of micronutrients and proteins while retaining farming-friendly characteristics such as high yield.
Dolores R. Piperno
National Museum of Natural History, Washington DC, and Smithsonian Tropical Research Institute, Balboa, Republic of Panama
An archaeologist tells how her research interest sheds light on the history of her favourite fruit.
My mother gave me a lot of sage advice during my childhood. This sometimes countered prevailing wisdom, such as her recommendation that I should eat bananas, not apples, every day.
The nutritional qualities of bananas were underappreciated when I was growing up in Philadelphia, Pennsylvania, although their value as a crop had been recognized millennia before.
A recent paper (B. Lejju et al. J. Archaeol. Sci. 33, 102–113; 2006) reports that bananas were being cultivated in Africa as long as 5,000 years ago.
The investigators reached this conclusion by studying phytoliths — highly durable pieces of silica that form in plant cells — that had been dug up in Uganda. I use phytoliths (and starch grains) in my own research into the history of agriculture, so it was more than just my fondness for bananas that drew me to this paper.
Phytoliths tell us which crops grew where and when, and so in turn can teach us about human cultures. Part of what makes this finding interesting is that bananas aren't native to the African continent. Wild bananas grow in eastern Asia, Australia and Melanesia. Hence the Ugandan bananas represent ancient human transport, probably through trade across the Indian Ocean with societies that were already growing the plant.
The age of the banana phytoliths also rivals presently available dates for the domestication of important, indigenous plants such as sorghum. However, I suspect that when phytolith and starch-grain analysis is applied to the history of native African crops, the date of their domestication will be pushed further back.
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