Site of the day: http://wired.com/
The days of whining drills and shrieking patients that can make a trip to the dentist an experience to dread may be numbered, according to scientists who claim that they may have found a way to regrow rotting teeth.
Researchers studying tooth development have singled out a gene that controls the growth of enamel, the hard outer layer of teeth, which cannot grow back naturally once it is damaged by tooth decay. The discovery sheds fresh light on the way teeth form and could pave the way for new dental treatments that heal decayed teeth by regenerating a layer of enamel, making traditional drilling and filling obsolete.
Scientists at Oregon State University found the gene after noticing that mice born without it grew teeth with no enamel covering.
Tooth enamel is the hardest tissue in the body and begins to form when humans are still embryos. Specialised cells called ameloblasts in the tooth bud make enamel by releasing calcium phosphate minerals into a protein "scaffold" that shapes them into tightly packed rods of enamel.
When our teeth are fully formed, they erupt from the gums and the enamel-forming cells die off, making it impossible for our teeth to regrow new enamel later. For most animals this is not a problem, but in humans, the large amount of sugar and starch in our diet is turned into acid by bacteria living on our teeth, which slowly dissolve the enamel to make a hole in the tooth. If untreated, cavities can cause life-threatening infections in the body.
If scientists can perfect a way of regrowing teeth and replacing the drill in the dentist's surgery, it could have important knock-on effects for patients.
In 2005, a survey by researchers at the University of Toronto found that 5% of patients were extremely anxious about visiting the dentist, and half were so afraid that they either cancelled their appointment or failed to show up. By missing appointments, patients risk turning a fairly minor dental problem into a serious risk to their health.
Last year, a poll by the Irish Dental Association found that parents passed on their fear of dentists to their children by telling them they were being brave or had nothing to fear from a visit.
Despite rates of dental cavities falling for the past 30 years, almost half of children and adolescents and more than 55% of adults in the UK are still affected by holes in their teeth.
Paul Sharpe, an expert on tooth development at the Dental Institute at King's College London, said: "If you could find some way of growing ameloblasts that make enamel, you could find a way to repair teeth.
"Any gene like this is worth understanding. The more we learn about it the more we can use the information to make biological models of tooth repair."
Prof Sharpe's own work focuses on using stem cells to regenerate teeth, but he said the introduction of the Human Tissue Act had made it difficult to obtain teeth from patients to do the work.
"We've probably lost a year because we've not been able to get hold of the right cells, and often these are from wisdom teeth that people are choosing to have removed," he said.
In the latest research, published in Proceedings of the National Academy of Sciences, a team led by Chrissa Kioussi and Mark Leid bred mice that lacked a gene known as Ctip2. They found that the gene was crucial for the enamel-producing cells to form and work properly.
By understanding the genetics of tooth development, Kioussi said it may be possible to repair damaged enamel and even produce new teeth in the laboratory.
Some groups have already succeeded in growing the soft tissues inside teeth, but they do not have the hard enamel covering needed to withstand chewing and biting.
"Enamel is one of the hardest coatings found in nature. It evolved to give carnivores the tough and long-lasting teeth they needed to survive," said Kioussi. "A lot of work would still be needed to bring this to human applications, but it should work. It could be really cool; a whole new approach to dental health," she said.
by Ian Sample
http://www.guardian.co.uk/education/2009/feb/24/dental-research-enamel-gene
Sunday, March 29, 2009
Sunday, March 22, 2009
LS9, Inc. introduces method to make engineering of bacterial cells faster
Site of the day: http://talk.dnadirect.com/
Rather than changing the genome letter by letter, as most genetic engineering is done, George Church and his colleagues have developed a new technology that can make 50 changes to a bacterial genome nearly simultaneously--an advance that could be used to greatly speed the creation of bacteria that are better at producing drugs, nutrients, or biofuels.
"What once took months now takes days," says Stephen del Cardayré, vice president of research and development at LS9, a biofuels company based in South San Francisco of which Church is a founder. LS9 soon plans to use the technology--called multiplex-automated genomic engineering, or MAGE--to accelerate development of bacterial cells that can produce low-cost renewable fuels and chemicals.
In the traditional stepwise approach to genetic engineering, scientists tinker gene by gene with a cell's metabolic system, attempting to rev up some reactions and dampen others. But this method is slow and unpredictable. A cell's metabolism consists of millions of intricately intertwined reactions, so making a specific change to a gene involved in one reaction may not produce the desired outcome, or may trigger harmful side effects.
Instead, Church and his collaborators attack the genome on a broad scale. They design numerous genetic changes targeting genes throughout the genome, and then implement them all at once, looking for the resulting bacterial strain that can best produce the desired product. "It allows you to make modifications to the genome much more rapidly than the traditional one-step processes we have," says Kristala Jones-Prather, a metabolic engineer at MIT who was not directly involved in the research.
Under the MAGE technology, scientists first generate 50 short strands of DNA, each containing a sequence similar to a gene or gene regulatory sequence in the target bacterial genome, but that has been updated in some way--incorporating a change that might make an enzyme more efficient, or boost production of a particular protein.
The DNA is mixed into a vial of bacteria, which is then put into a custom-made machine designed in Church's lab. In the machine, the mixture is subjected to a precisely choreographed routine of temperature and chemical cycles that encourage the bacterial cells to take up the foreign DNA, swapping it into their genomes in place of the native piece it resembles. The single-stranded pieces of DNA are thought to "fake out the cell's DNA replication machinery, sneaking in and filling a gap" during the replication process, says Church. Each generation of the rapidly reproducing bacteria takes up more of the foreign DNA, ultimately producing a population that has all the desired genetic changes.
As a test run of the device, Church and his team created bacteria that could more efficiently produce lycopene, an antioxidant abundant in tomatoes. They designed DNA strands targeting genes known to be involved in lycopene production, and then monitored multiple tubes of engineered bacteria for production of the bright-red compound. In just three days, they had generated a strain that could produce five times more lycopene, according to findings presented at a conference at Harvard this month. The best lycopene producer had 24 genetic changes--four that completed blocked production of the gene's protein, and 20 that resulted in small or large changes in the expression of that gene.
Church and his collaborators, who ultimately plan on making a commercial version of the device, are now working on creating different types of chemicals, including biofuels and drug precursors.
by Emily Singer
Rather than changing the genome letter by letter, as most genetic engineering is done, George Church and his colleagues have developed a new technology that can make 50 changes to a bacterial genome nearly simultaneously--an advance that could be used to greatly speed the creation of bacteria that are better at producing drugs, nutrients, or biofuels.
"What once took months now takes days," says Stephen del Cardayré, vice president of research and development at LS9, a biofuels company based in South San Francisco of which Church is a founder. LS9 soon plans to use the technology--called multiplex-automated genomic engineering, or MAGE--to accelerate development of bacterial cells that can produce low-cost renewable fuels and chemicals.
In the traditional stepwise approach to genetic engineering, scientists tinker gene by gene with a cell's metabolic system, attempting to rev up some reactions and dampen others. But this method is slow and unpredictable. A cell's metabolism consists of millions of intricately intertwined reactions, so making a specific change to a gene involved in one reaction may not produce the desired outcome, or may trigger harmful side effects.
Instead, Church and his collaborators attack the genome on a broad scale. They design numerous genetic changes targeting genes throughout the genome, and then implement them all at once, looking for the resulting bacterial strain that can best produce the desired product. "It allows you to make modifications to the genome much more rapidly than the traditional one-step processes we have," says Kristala Jones-Prather, a metabolic engineer at MIT who was not directly involved in the research.
Under the MAGE technology, scientists first generate 50 short strands of DNA, each containing a sequence similar to a gene or gene regulatory sequence in the target bacterial genome, but that has been updated in some way--incorporating a change that might make an enzyme more efficient, or boost production of a particular protein.
The DNA is mixed into a vial of bacteria, which is then put into a custom-made machine designed in Church's lab. In the machine, the mixture is subjected to a precisely choreographed routine of temperature and chemical cycles that encourage the bacterial cells to take up the foreign DNA, swapping it into their genomes in place of the native piece it resembles. The single-stranded pieces of DNA are thought to "fake out the cell's DNA replication machinery, sneaking in and filling a gap" during the replication process, says Church. Each generation of the rapidly reproducing bacteria takes up more of the foreign DNA, ultimately producing a population that has all the desired genetic changes.
As a test run of the device, Church and his team created bacteria that could more efficiently produce lycopene, an antioxidant abundant in tomatoes. They designed DNA strands targeting genes known to be involved in lycopene production, and then monitored multiple tubes of engineered bacteria for production of the bright-red compound. In just three days, they had generated a strain that could produce five times more lycopene, according to findings presented at a conference at Harvard this month. The best lycopene producer had 24 genetic changes--four that completed blocked production of the gene's protein, and 20 that resulted in small or large changes in the expression of that gene.
Church and his collaborators, who ultimately plan on making a commercial version of the device, are now working on creating different types of chemicals, including biofuels and drug precursors.
by Emily Singer
Saturday, March 7, 2009
Single-molecular Switch Advancement
Site of the day: http://www.wired.com
Mechanically controlled binary conductance switching of a single-molecule junction
Article:
http://www.nature.com/nnano/journal/vaop/ncurrent/abs/nnano.2009.10.html
Preprint of the article is available at:
http://arxiv.org/pdf/0901.1139v1
Mechanically controlled binary conductance switching of a single-molecule junction
Article:
http://www.nature.com/nnano/journal/vaop/ncurrent/abs/nnano.2009.10.html
Preprint of the article is available at:
http://arxiv.org/pdf/0901.1139v1
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