Scientists from the Broad Institute report in this week's Science a number of previously unknown mechanisms microbes use to defend against viral threats. Bacteria and archaea are known to employ dedicated antiviral defense systems such as CRISPR and restriction endonucleases, but the enormous diversity of viruses suggests there are more such systems to be discovered. To investigate, the researchers used a computational approach for defense gene prediction and heterologous reconstitution to analyze all bacterial and archaeal genomes available in GenBank as of November 2018. They discovered 29 widespread antiviral gene cassettes, collectively present in 32 percent of all sequenced bacterial and archaeal genomes, that mediate protection against specific bacteriophages using enzymatic activities not previously implicated in antiviral defense such as RNA editing. The researchers also computationally predict a diverse set of other putative defense genes to be characterized.
Using CRISPR-Cas9 genome editing, a group of scientists from Harvard Medical School generated fat cells in mice that prevent obesity and metabolic syndrome. In a study appearing in Science Translational Medicine, the researchers used CRISPR to engineer white adipose tissue, which stores excess fuel, to act like brown adipose tissue, which is specific for energy dissipation. Specifically, they altered the white adipose tissue so that it expresses higher amounts of uncoupling protein 1, a membrane protein used by brown adipose tissue to break down fat to generate heat. When the CRISPR-modified cells — called human brown-like, or HUMBLE, cells — were introduced into obese mice, the animals showed a sustained improvement in glucose tolerance and insulin sensitivity, as well as increased energy expenditure. The investigators attributed the effects of the HUMBLE cells to their ability to boost nitric oxide signaling, which activated brown adipose tissue.