Posts Tagged ‘genetics’
We Incorporate Genetic Information From the Food We Eat, New Study Finds
MicroRNAs, or miRNAs, are little strands of RNA that selectively bind to matching sequences of messenger RNA, resulting in repression of those genes. Their role has only been understood in the last decade or so, but miRNAs are currently believed to take part in a vast number of processes in both plants and animals.
Chen-Yu Zhang and colleagues found plant miRNA sequences in the tissue of animals that ate those plants. One of them, called MIR168a, is produced by rice and abundantly found in the blood of the Chinese humans studied. In experiments, MIR168a showed the ability to affect gene expression in mouse, inhibiting the liver's ability to filter out LDL, the lipoprotein with the street name of "bad cholesterol."
This finding reveals an entirely new mechanism of physiological interaction, which could have significant medical applications as a therapeutic vector as well as explaining processes that are poorly understood (Zhang's example is Chinese herbal medicine). MicroRNA is also used in the genetic engineering of crops, as a method of RNA interference.
Scientists Who Cloned Dolly the Sheep Plan to Clone Endangered Scottish Wildcats Using Eggs From Spayed Pets
The Scottish wildcat, Felis silvestris silvestris, is related to other species of wildcats in Europe, but has been wiped out in England and Wales. Only about 400 animals remain, according to researchers at the Edinburgh Science Triangle. Researchers believe the cats could be . The purity of their gene pool is threatened by interbreeding with feral domestic cats, which has sparked an effort to spray the cats for free. It turns out that this hybridization could actually be the wildcats’ salvation, according to embryologist Bill Ritchie.
Eggs from the spayed cats could be the starting material for the new cloning process, according to Ritchie.
He would identify pure-bred wildcats through genetic testing, and then take a skin sample and culture some cells. The cells would be used to clone the animals, using the feral cat eggs as a host. The spaying program, which is taking place in the Eastern Cairngorms, would be a good source of lots of eggs, Ritchie said.
“Several cat species have been cloned using the domestic cat, as well as the wolf using dog eggs and the Mouflon (a type of wild sheep) using the domestic sheep,” Ritchie said in a news release.
It would work by developing the immature spayed-egg cells in vitro, to make them suitable for cloning. Then the eggs would be used to produce an embryo that contains the genetic material of the donor wildcat. This embryo would be transplanted in a surrogate cat.
By definition, this whole process does not increase the gene pool of the endangered cats — but it could be a way to ensure that breeding animals will always have a potential mate. Ritchie envisions using the same process in zoos, where healthy animals often do not breed.
The project has some funding from Genecom Ltd, a commercialization arm of the Moredun Research Institute in Midlothian, as well as the UK-based Institute for Animal Health, but Ritchie is looking for further financial backing to continue the cloning effort, according to the news release.
This Worm Is the First Animal Engineered to Produce Biological Blocks Not Found in Nature
Meet the 21st amino acid
A quick biology primer, just in case high school biology isn't so fresh. DNA is of course the blueprint for all of our biological stuff. It gives instructions on how the amino acids should arrange themselves into proteins, which pick up the heavy lifting of life from there. There are just 20 amino acids, arranged in different combinations, that are encoded in the genome.
The Cambridge team has created nematode worms that generate a 21st, never before seen amino acid. That’s big, because it basically enables a new resolution in genetic manipulation, a kind of “atom-by-atom control” over biological molecules, as one biologist put it to the BBC.
The artificial protein produced by their artificially enhanced nematodes simply contains a fluorescent dye that glows red under UV light--a test to ensure that their genetic manipulation worked. But ostensibly scientists could do all kinds of things with this technique by producing all kinds of novel amino acids and proteins. Unlike an artificial recreation of something natural--something akin to the Venter Institute’s --these nematodes represent that creation of something wholly new.
Keep an eye on this story. It’s bursting with potential for mind-blowing scientific innovation and chilling sci-fi screenplays.
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Mice Engineered to Lack Muscle Contraction Gene Have Superior Endurance (and Humans Might, Too)
Mice that lack this gene, which is related to muscle contraction, can than their counterparts, a new study says — suggesting a genetic predisposition to endurance in some athletes.
Physiologists led by Tejvir Khurana at the University of Pennsylvania were studying IL-15Rα, which had been linked to proteins associated with muscle contraction. They engineered mice to lack that gene, and recorded the mice’s activity. Every night, the knockout mice ran six times farther than normal mice, according to the .
The team dissected the muscles in these marathon mice, and found the muscles had more fibers and more mitochondria, the power plants of cells, Science NOW reports. This meant the muscles took longer to tire and longer to use up their energy supplies. The researchers found that the lack of IL-15Rα coaxed one type of muscle cell to turn into another type — from fast-twitch, easily tired muscles into slower-contracting, longer-endurance muscles.
It turns out that endurance athletes also have IL-15Rα variations, which might help explain their stamina. Khurana et. al worked with some Australian researchers to study genetic samples from Olympians and other world-class athletes, and found certain genetic variants were more common in long-distance athletes than in sprinters, for instance.
The research is reported in the .
More work must be done to explain why the IL-15Rα knockout mice had such a proclivity for physical activity — no one coaxed them to run six times longer than their friends, they just did. So it’s not clear whether a lack of IL-15Rα made them hyperactive as well as tenacious. But “the work raises the possibility that drugs blocking IL-15Rα could one day enhance endurance,” Science NOW reports.
Until then, looks like I will just have to keep training.
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New Genome Editing Method Helps Scientists Rewrite Whole Sections of the Code of Life
Using a new genome engineering method, researchers from Harvard University and MIT were able to systematically replace one three-letter DNA “word,” or codon, with another one, throughout the entire genome. Their method reimagines genomes as editable templates, allowing entire sections to be rewritten without interrupting the overall organizational structure.
Ever since genome sequences were unraveled, scientists have been experimenting with ways to edit them, to give cells new capabilities and to cure diseases. But progress has been slow, in part because the editing job must be incredibly precise — one misplaced allele on a chromosome can be lethal. Introducing individual changes is therefore laborious and difficult.
Genetic scissors like zinc-finger nucleases can do the job, glomming on to certain sequences of a genome and cutting it out. Engineered viruses can then bring new DNA to the targeted area. Just last month, researchers successfully that cause hemophilia, in a study involving living mice.
Rather than using scissors, this new method is akin to the find-and-replace function on your word processor, seeking out individual codons and replacing all of them with something new. The researchers used E. coli bacteria and edited a codon that only appears 314 times in the genome, spelled TAG.
Most codons spell out the sequence of an amino acid, as a Harvard Medical School explains. But some codons direct a cell to stop adding amino acids to a protein chain. TAG is one such stop codon, and it happens to be the rarest word in the E. coli genome. The team used a method called multiplex automated genome engineering, or MAGE, to replace the TAG codon with another stop codon, TAA.
MAGE locates specific DNA sequences and replaces them with a new sequence as the cell copies its DNA. The team made 32 E. coli strains, each of which had 10 TAG codons replaced. Then they used a new technique called conjugative assembly genome engineering (CAGE), which allowed them to control the process that bacteria use to swap genetic material.
An evolutionary tournament of sorts reduced the number of strains to 16, each with double the amount of TAG edits that it started with; ultimately, a final four strains had one-fourth of all their TAGs replaced, .
The researchers believe they’re on track to replace all 314 of them — without harming the cells in any way.
The next step would be to take out the genetic sequences that allow the cell to read the TAG stop instructions. This machinery could then be used for an entirely new purpose, like encoding a new protein or function.
The research is described in today's issue of the journal Science.
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First Successful Use of Genome Editing In Living Animals Cures Hemophilia In Mice
Scientists say the research is a major step forward for gene therapy, which has long promised to cure disease by editing genetic sequences.
The therapy is based on enzymes called , which serve as a sort of genetic scissors. The enzymes are engineered to match a specific gene location on a chromosome, where they snip through DNA’s double helix.
In this case, researchers led by Katherine A. High, a hematologist and gene therapy expert at The Children’s Hospital of Philadelphia, used ZFN proteins that were engineered to snip through the location of a genetic mutation that causes hemophilia. Hemophiliacs lack a blood-clotting factor made by the liver that helps stanch bleeding, so their blood cannot clot, meaning minor injuries can be life-threatening.
High and colleagues had to take another step in their research, because hemophilic mice have a different genetic mutation than humans. They engineered mice to express the faulty human sequence, located on the F9 gene, and they designed ZFNs to cut through it. Then they engineered a virus that targets the liver (where the blood clotting factor is made) to carry the normal, unmutated version of F9.
As a result, the mutated section was removed, and the unmutated gene was inserted instead. Then the DNA molecule is stimulated to repair itself, sewing the new gene in place.
This is an improvement over other genetic editing techniques that use viruses to cut and paste the new genes. Although they have been shown to work, viral therapy has some inherent problems, including unpredictable chromosomal insertion, which can induce unwanted mutations. But the ZFN is designed to home in on a precise location of mutated DNA.
After this treatment, the animals’ blood clotted in 44 seconds, compared with more than a minute for hemophiliac mice, .
The study shows that zinc finger proteins and replacement genes can be used to induce changes in living animals, which is promising for a wide range of therapies. For instance, other researchers are using ZFNs to disrupt a gene that makes a receptor used by the AIDS virus, as the . People without that gene, CCR5, are naturally immune to HIV.
The mouse study is reported in this week's issue of the journal Nature.
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Introducing Genome Wowser, The iPad App That Lets You Browse the Human Genome
Genome Wowser--the name is derived from the Genome Browser Website set up by UCSC in 2000, but with additional “wow”--is kind of like a Google Maps for the genome. You can search for a specific gene by entering its name in the search box, or you can simply browse for points of interest. Annotations added by researchers serve as guideposts, offering insight into genes’ particular known or supposed expressions.
There’s also information embedded about epigenetics--how genes are modified by chemical processes, and all of that information is updated regularly. Factor in the upcoming versions that will include more than three dozen other species--including cats, dogs, chimpanzees, and 11 species of fruit flies--and Genome Wowser is a pretty powerful tool for geneticists and the scientifically curious alike. Try doing all of that on Kindle.