the-BA : Science News Digest

T. rex (Image copyright: istockphoto.com)

In the science news this week: protein points to chicken as T. rex’s closest living relative, the first common genetic risk factor found for obesity and how to spot an extraterrestrial plant...

This week, the first molecular evidence to support the notion that birds evolved from dinosaurs was published in the journal Science. Researchers extracted and sequenced proteins from a 68 million-year-old Tyrannosaurus rex leg bone and compared them to known protein sequences in living animals. They found the greatest similarity was to modern chicken proteins.

Dr John Asara, one of the study’s authors, told the Guardian: ‘If we had more species in the database to compare it to, such as alligator or crocodile, which have not been sequenced yet, we may also find matches to those species. Based on this study, it looks like chickens might be the closest amongst all species that are present in today’s genome databases.’

Seven different T. rex proteins were obtained from collagen fibre that remained in the fossil. They are by far the oldest proteins ever sequenced. Now that it appears fossilisation doesn’t necessarily destroy delicate organic molecules such as protein, scientists are excited at the prospect of a new era of paleontology where molecules can be used to investigate patterns and rates of evolution.

The Times reported another of the week’s big stories: the discovery of the first clear genetic link to obesity that is carried by a large proportion of the population.

People who carry two copies of a certain version of the FTO gene are 70 per cent more likely to be obese than those who inherit two copies of the alternative genetic variant. One in six individuals were found to possess this high-risk genetic make-up. They had 15 per cent more fat and were an average of 3 kg heavier. A further 50 per cent were classed as medium risk. They possessed one copy of each FTO variant and had a 30 per cent higher risk of obesity.

The role of FTO as an obesity risk factor came to light through a study looking into the genetic origins of type 2 diabetes. The Case Control Consortium compared the genomes of 2,000 people with type 2 diabetes to 3,000 healthy controls. A variant of the FTO gene was found to be more common among those with the disease. However, when the data was adjusted for obesity, the effect disappeared. The scientists then studied a further 37,000 people to see whether FTO actually influenced obesity instead.

Its biological role still remains to be understood, but the leader of the study, Professor Mark McCarthy of the University of Oxford, hopes that the finding will help improve understanding of why some people are more obese and that new insights will pave the way for novel methods of treating obesity.

The Guardian reported a scientific breakthrough in which immature human sperm cells have been created from bone marrow stem cells. The researchers involved believe fully developed sperm cells could be achieved following a further three to five years of work. Eventually, this may offer opportunities to restore fertility in men who, for example, have become infertile due to cancer treatment. The same team previously produced mouse sperm from stem cells and used these to successfully fertilise eggs.

RNA interference – a technique which allows scientists to “silence” specific genes – could revolutionise cancer treatment, a new study has shown. Scientists have conducted pioneering experiments in which switching off genes apparently turned on by the cancer process hugely increased the sensitivity of tumour cells to anti-cancer drugs. This could potentially put an end to the awful side effects of chemotherapy by enabling treatment using much lower doses, although the scientists involved emphasised that years of further testing in the laboratory and animal trials remain before it could be used in clinical trials on cancer patients.

By screening more than 21,000 genes, scientists found 87 that can influence the sensitivity of a tumour cell to chemotherapy. Six genes were particularly linked with sensitivity to the drug Taxol. In one experiment, lung cancer tumour cells were made 10,000 times more susceptible to it. However, the genes uncovered so far appear to be highly specific for this particular drug, as the approach didn’t show such dramatic effects when others were tested.

‘Chemotherapy is a very blunt instrument. It makes people sick, and its effects are very inconsistent,’ said Professor Michael White in the Independent. ‘Identifying genes that make chemotherapy drugs more potent at lower doses is a first step toward alleviating these effects in patients.’

In other news, questions were raised in the Guardian about the sense in planting trees to offset carbon emissions after new research revealed that, unless they are planted in the tropics, they could actually be contributing to global warming.

Computer models conducted by two US atmospheric and global ecology scientists reveal that forests outside of a narrow band around the equator actually trap more heat than they help to avoid through their absorption of carbon dioxide.

‘It is a win-win situation in the tropics because trees in the tropics, in addition to absorbing carbon dioxide, promote convection clouds that help to cool the planet,’ said Dr Govindasamy Bala. ‘In other locations, the warming from the albedo effect [the reflection of sunlight back into space] either cancels or exceeds the net cooling from the other two effects.’

His colleague Dr Ken Caldeira hastened to add that we should not rush to chop down trees outside the tropics: ‘Preservation of ecosystems is a primary goal of preventing global warming, and the destruction of ecosystems to prevent global warming would be a counterproductive and perverse strategy.’ The research does, however, add weight to the argument that we should look to other ways of cutting carbon rather than relying on forestry schemes.

Nice red grass, or yellow trees... studies carried out by scientists suggest alien plant life is just as likely to be these colours as green. Indeed, reported the Times, if any exists on other planets it is probably coloured the whole spectrum except blue. This is because the colour of foliage depends on the spectrum of light available from the local sun. Blue light is particularly valuable as a source of energy for plants through photosynthesis, since it is highly energetic. Therefore, it is more likely to be absorbed than reflected.

By analysing the light emitted from stars, astronomers will be able to determine the likely colour of foliage on orbiting planets and hence have a guide of what to look out for. The studies were carried out as part of the preparation for NASA and European Space Agency projects that will put telescopes into space to search for extraterrestrial life.

In other space-related news, the BBC reported that scientists have found the first evidence of water vapour in the atmosphere of a planet outside our Solar System – on HD 209458b, a gas giant in the Pegasus constellation.

And finally...

They may make unusual lab assistants, but penguins are the new recruits that are helping scientists measure fish stocks in the Southern Ocean. The usual methods used are inexact and costly, so instead researchers from Birmingham are using king penguins who naturally inhabit the area to assess the effects of over-fishing and global warming on their local ecosystem.

The experiments work on the basis that you can calculate the availability of the penguin’s food – lanternfish – by measuring the energy that the penguin has to expend to find it. The fewer fish there are, the harder the penguin will have to work to find any.

Smart tags implanted into the abdomens of 50 penguins record the temperature at the back of the animals’ throats. This provides feedback about when and how much each penguin eats as a small temperature drop occurs when a fish is swallowed. A hydrostatic sensor measures pressure and provides information about the depth to which the penguin needs to dive to find food. The heart rate and oxygen consumption of the penguins are monitored while they run on a specially adapted treadmill and swim in a custom-built water channel. This data enables the researchers to estimate the energy expended by the penguins during their hunting excursions using recorded heart-rate information.

Unfortunately, preliminary data indicates that the penguins are having to work harder to find less food. Project leader Dr Lewis Halsey believes that without this kind or research the implication for the penguins he works with could be drastic. He told the Independent: ‘If fishing and the warming of the seas goes on at this rate, it could result in reduced breeding success, which would be a tragedy. It’s difficult to get across how phenomenal these creatures are.’

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