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Erasing a genetic mutation. Using a new gene-editing system based on bacterial proteins, MIT researchers have cured mice of a rare liver disorder caused by a single genetic mutation.

Erasing a genetic mutation

The findings, described in the March 30 issue of Nature Biotechnology, offer the first evidence that this gene-editing technique, known as CRISPR, can reverse disease symptoms in living animals. CRISPR, which offers an easy way to snip out mutated DNA and replace it with the correct sequence, holds potential for treating many genetic disorders, according to the research team. “What’s exciting about this approach is that we can actually correct a defective gene in a living adult animal,” says Daniel Anderson, the Samuel A. Goldblith Associate Professor of Chemical Engineering at MIT, a member of the Koch Institute for Integrative Cancer Research, and the senior author of the paper. The recently developed CRISPR system relies on cellular machinery that bacteria use to defend themselves from viral infection.

Disease correction. CRISPR-Cas immunity in prokaryotes : Nature. The CRISPR web page. The CRISPR page at CNB by Davide Seruggia (Boston Children's Hospital) and Lluís Montoliu (CNB-CSIC) Lluís Montoliu's Lab Web Page LAST UPDATED: 8 November 2015 What is CRISPR-Cas9?

The CRISPR web page

Jennifer Doudna, Emmanuelle Charpentier and Feng Zhang (from left to right). Chinese paper on embryo engineering splits scientific community. The announcement that a Chinese team had altered the genetics of a human embryo for the first time has ignited a firestorm of controversy around the world and renewed recent calls for a moratorium on any attempt to establish a pregnancy with such an engineered embryo.

Chinese paper on embryo engineering splits scientific community

But it has also underscored that although scientists are united in their opposition to any clinical application of such embryo manipulation, they are split on the value of basic research that involves genetically modifying human embryos. In China itself, where the precedent-setting research is big news and some in the public have expressed concern on the Internet about the embryo experiments, "most scientists are more positive," says Guo-Qiang Chen, a microbiologist at Tsinghua University in Beijing. "My personal opinion is that as long as they can control the consequences they should continue this work.”

That view is echoed by many outside of China as well. Still, the paper drew anger from some quarters. Chinese scientists genetically modify human embryos. Dr.

Chinese scientists genetically modify human embryos

Yorgos Nikas/SPL Human embryos are at the centre of a debate over the ethics of gene editing. In a world first, Chinese scientists have reported editing the genomes of human embryos. The results are published1 in the online journal Protein & Cell and confirm widespread rumours that such experiments had been conducted — rumours that sparked a high-profile debate last month2, 3 about the ethical implications of such work. In the paper, researchers led by Junjiu Huang, a gene-function researcher at Sun Yat-sen University in Guangzhou, tried to head off such concerns by using 'non-viable' embryos, which cannot result in a live birth, that were obtained from local fertility clinics. "I believe this is the first report of CRISPR/Cas9 applied to human pre-implantation embryos and as such the study is a landmark, as well as a cautionary tale," says George Daley, a stem-cell biologist at Harvard Medical School in Boston, Massachusetts.

Problematic gene Serious obstacles Ethical questions. Chinese paper on embryo engineering splits scientific community. Development and Applications of CRISPR-Cas9 for Genome Engineering. Recent advances in genome engineering technologies based on the CRISPR-associated RNA-guided endonuclease Cas9 are enabling the systematic interrogation of mammalian genome function.

Development and Applications of CRISPR-Cas9 for Genome Engineering

Analogous to the search function in modern word processors, Cas9 can be guided to specific locations within complex genomes by a short RNA search string. Using this system, DNA sequences within the endogenous genome and their functional outputs are now easily edited or modulated in virtually any organism of choice. Cas9-mediated genetic perturbation is simple and scalable, empowering researchers to elucidate the functional organization of the genome at the systems level and establish causal linkages between genetic variations and biological phenotypes. In this Review, we describe the development and applications of Cas9 for a variety of research or translational applications while highlighting challenges as well as future directions. Technical Note: Potential to Supercharge CRISPR Gene Editing by Combining with rAAV. Genome editing has had a real boost recently through the interest in CRISPR technology.

Technical Note: Potential to Supercharge CRISPR Gene Editing by Combining with rAAV

However, whilst the majority of CRISPR papers being published utilize the technology to functionally disrupt (knockout) a gene using an NHEJ-based mis-repair system, using CRISPR to purposefully edit the genome in a more controlled manner is a slightly more challenging proposition that calls upon the endogenous homology-directed repair system and requires one additional component not needed in knockout experiments—a “donor” DNA template. For the most part, researchers have been using either single-stranded oligos or double-stranded plasmids to provide this homology template. It has been known for some time that rAAV is able to drive levels of homologous recombination that are up to 1,000-fold higher than when using a simple plasmid. Despite this vast improvement compared with plasmids, the levels of recombination seen are still relatively modest using rAAV alone. VIDEO: GENESIS™ Precision Genome Editing with CRISPR and rAAV.

CRISPR-Cas9: Harbinger of Human Gene Editing and Its Ethical Turmoil. Image by Kevin Schneider.

CRISPR-Cas9: Harbinger of Human Gene Editing and Its Ethical Turmoil

CRISPR: the good, the bad and the unknown.