Later On

A blog written for those whose interests more or less match mine.

Gene hacking

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Very interesting article in the New Yorker by Michael Specter on how neatly we can now work on genes:

At thirty-four, Feng Zhang is the youngest member of the core faculty at the Broad Institute of Harvard and M.I.T. He is also among the most accomplished. In 1999, while still a high-school student, in Des Moines, Zhang found a structural protein capable of preventing retroviruses like H.I.V. from infecting human cells. The project earned him third place in the Intel Science Talent Search, and he applied the fifty thousand dollars in prize money toward tuition at Harvard, where he studied chemistry and physics. By the time he received his doctorate, from Stanford, in 2009, he had shifted gears, helping to create optogenetics, a powerful new discipline that enables scientists to use light to study the behavior of individual neurons.

Zhang decided to become a biological engineer, forging tools to repair the broken genes that are responsible for many of humanity’s most intractable afflictions. The following year, he returned to Harvard, as a member of the Society of Fellows, and became the first scientist to use a modular set of proteins, called TALEs, to control the genes of a mammal. “Imagine being able to manipulate a specific region of DNA . . . almost as easily as correcting a typo,” one molecular biologist wrote, referring toTALEs, which stands for transcription activator-like effectors. He concluded that although such an advance “will probably never happen,” the new technology was as close as scientists might get.

Having already helped assemble two critical constituents of the genetic toolbox used in thousands of labs throughout the world, Zhang was invited, at the age of twenty-nine, to create his own research team at the Broad. One day soon after his arrival, he attended a meeting during which one of his colleagues mentioned that he had encountered a curious region of DNA in some bacteria he had been studying. He referred to it as a CRISPR sequence.

“I had never heard that word,” Zhang told me recently as we sat in his office, which looks out across the Charles River and Beacon Hill. Zhang has a perfectly round face, its shape accentuated by rectangular wire-rimmed glasses and a bowl cut. “So I went to Google just to see what was there,” he said. Zhang read every paper he could; five years later, he still seemed surprised by what he found. CRISPR, he learned, was a strange cluster of DNA sequences that could recognize invading viruses, deploy a special enzyme to chop them into pieces, and use the viral shards that remained to form a rudimentary immune system. The sequences, identical strings of nucleotides that could be read the same way backward and forward, looked like Morse code, a series of dashes punctuated by an occasional dot. The system had an awkward name—clustered regularly interspaced short palindromic repeats—but a memorable acronym.

CRISPR has two components. The first is essentially a cellular scalpel that cuts DNA. The other consists of RNA, the molecule most often used to transmit biological information throughout the genome. It serves as a guide, leading the scalpel on a search past thousands of genes until it finds and fixes itself to the precise string of nucleotides it needs to cut. It has been clear at least since Louis Pasteur did some of his earliest experiments into the germ theory of disease, in the nineteenth century, that the immune systems of humans and other vertebrates are capable of adapting to new threats. But few scientists had considered the possibility that single bacterial cells could defend themselves in the same way. The day after Zhang heard about CRISPR, he flew to Florida for a genetics conference. Rather than attend the meetings, however, he stayed in his hotel room and kept Googling. “I just sat there reading every paper on CRISPR I could find,” he said. “The more I read, the harder it was to contain my excitement.”

It didn’t take Zhang or other scientists long to realize that, if nature could turn these molecules into the genetic equivalent of a global positioning system, so could we. Researchers soon learned how to create synthetic versions of the RNA guides and program them to deliver their cargo to virtually any cell. Once the enzyme locks onto the matching DNA sequence, it can cut and paste nucleotides with the precision we have come to expect from the search-and-replace function of a word processor. “This was a finding of mind-boggling importance,” Zhang told me. “And it set off a cascade of experiments that have transformed genetic research.”

With CRISPR, scientists can change, delete, and replace genes in any animal, including us.

Continue reading.

Regarding that last sentence, I cannot understand why the same technique would not work on plants as well, but the author is at some pains to say specifically that it works in animals, carefully avoiding making any claims about the technique as applied to plants.

UPDATE: Michael Specter responded to a tweet from me and says that it does indeed work with plants, which makes me wonder why he restricts his statement in the article to animals.

UPDATE More about CRISPR in this article in the NY Times Magazine, which is more informative.

Written by LeisureGuy

9 November 2015 at 8:35 am

Posted in Science

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