Monthly Archives: September 2014

The human body is pretty great, but it could use a few tweaks from time to time.

Thats the philosophy of a group of scientists developing a way to edit genomes, a cutting-edge field that could be the answer to many significant diseases and help researchers better understand the human body.

Thanks to these discoveries, scientists can now replace specific parts of the DNA of cells, making a disease weaker or a person less susceptible to the disease, for example. In the case of HIV, which is unable to infect people without a specific protein, genome editing can modify the specific part of the genome so the person no longer produces the protein and the person can no longer be infected with HIV.

We take out cells, correct it ... and put the cell back into the person, said Feng Zhang, a researcher at the Broad Institute in Cambridge. Its a biotechnology that allows us to go into the genome, the DNA of a cell, and make very exact changes within the DNA.

It is process that can take weeks, requiring the removal of in the case of HIV all of the blood cells so the change can be made to the cells.

Zhang said sickle cell anemia is another disease that could be tackled by genome editing, but any virus including Ebola that has a mutation that can be exploited at the genetic level could be addressed by the process.

He is credited with developing CRISPR, a new method of genome editing that his colleagues say made the practice dramatically more widespread.

Any lab with any biological expertise can do it, said Charles Gersbach of Duke University, who is studying genome editing for genetic diseases.

By breaking the DNA in a specific place, the cells self-repair mechanism is triggered, but instead of reforming the same DNA sequence, CRISPR provides a new template.

When you make a cut in the region you want to fix, you can fool the cell into putting in the right information, Zhang said.

More:
Fighting diseases via genome editing

Scientists said they believe they are on the cusp of developing new strains of livestock using DNA technology that may improve meat and milk production while alleviating consumer fears, according to an MIT Technology Review article published in September.

A June poll by ABC News found that barely more than a third of the public believes that genetically modified foods are safe to eat, yet a consensus among scientists and industry professionals alike said the exact opposite.

While there is controversy surrounding genetically modified organisms, most concerns center around genetically modified plants, developed by splicing specific DNA from one plant species into another. Scientists are developing a new technology called genome editing they believe will revitalize the concept of genetically modified livestock since the process involves genes in animals that are currently in the food supply.

Jennifer Bormann, associate professor of animal breeding and genetics, said using this technology can improve cattle quality without changing the quality of meat or milk consumers get from the animal.

When changing one specific gene, all other genes are unaffected, Bormann said. It would be possible to change a gene that affects meat or milk. If, for example, you wanted to make the meat more tender, you might change a gene that has been proven to make meat tender.

She also said the genome editing technology doesnt create any food safety concerns because, we have been doing it for a long time in plants, and the same product could be created without the use of this technology.

We could do the same thing with traditional breeding by crossing and backcrossing repeatedly to introgress the gene of interest, Bormann said. It would just take many generations of crossing and many years.

Karen Batra, director of food and agriculture communications for the Biotechnology Industry Organization, said genetic engineering is the deliberate modification of the animals genome using techniques of modern biotechnology.

Many might be surprised to know that genetically engineered animals are just like normal cows, pigs, goats and fish only better, Batra said. They all contain a specific gene that makes them better than their conventional counterparts.

Batra also said that by incorporating genes from other organisms in a process called transgenesis, genetically engineered animals are being developed to address five broad goals. The goals are to advance human health, enhance food production and quality, mitigate environmental impact, optimize animal welfare and improve industrial products.

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Genome editing opens possibilities for genetically modified livestock

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New findings by scientists at the University of California, Santa Cruz, suggest that an evolutionary arms race between rival elements within the genomes of primates drove the evolution of complex regulatory networks that orchestrate the activity of genes in every cell of our bodies.

The arms race is between mobile DNA sequences known as "retrotransposons" (a.k.a. "jumping genes") and the genes that have evolved to control them. The UC Santa Cruz researchers have, for the first time, identified genes in humans that make repressor proteins to shut down specific jumping genes. The researchers also traced the rapid evolution of the repressor genes in the primate lineage.

Their findings, published September 28 in Nature, show that over evolutionary time, primate genomes have undergone repeated episodes in which mutations in jumping genes allowed them to escape repression, which drove the evolution of new repressor genes, and so on. Furthermore, their findings suggest that repressor genes that originally evolved to shut down jumping genes have since come to play other regulatory roles in the genome.

"We have basically the same 20,000 protein-coding genes as a frog, yet our genome is much more complicated, with more layers of gene regulation. This study helps explain how that came about," said Sofie Salama, a research associate at the UC Santa Cruz Genomics Institute who led the study.

Retrotransposons are thought to be remnants of ancient viruses that infected early animals and inserted their genes into the genome long before humans evolved. Now they can only replicate themselves within the genome. Depending on where a new copy gets inserted into the genome, a jumping event can disrupt normal genes and cause disease. Often the effect is neutral, simply adding to the overall size of the genome. Very rarely the effect might be advantageous, because the added DNA can itself be a source of new regulatory elements that enhance gene expression. But the high probability of deleterious effects means natural selection favors the evolution of mechanisms to prevent jumping events.

Scientists estimate that jumping genes or "transposable elements" account for at least 50 percent of the human genome, and retrotransposons are by far the most common type.

"There have been successive waves of retrotransposon activity in primate evolution, when a transposable element changed to become expressed and replicated itself throughout the genome until something turned it off," Salama said. "We've discovered a major mechanism by which the genome is able to shut down these mobile DNA elements."

The repressors identified in the new study belong to a large family of proteins known as "KRAB zinc finger proteins." These are DNA-binding proteins that repress gene activity, and they constitute the largest family of gene-regulating proteins in mammals. The human genome has over 400 genes for KRAB zinc finger proteins, and about 170 of them have emerged since primates diverged from other mammals.

According to Salama, her team's findings support the idea that expansion of this family of repressor genes occurred in response to waves of retrotransposon activity. Because repression of a jumping gene also affects genes located near it on the chromosome, the researchers suspect that these repressors have been co-opted for other gene-regulatory functions, and that those other functions have persisted and evolved long after the jumping genes the repressors originally turned off have degraded due to the accumulation of random mutations.

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Human genome was shaped by an evolutionary arms race with itself