CRISPR Converts Microbes to Tape Recorders

GEN News Highlights, 27 Nov 2017,

Scientists have created a CRISPR/Cas system in E. coli that allows for the recording of events and the time at which they occurred.  This was done by having the cell insert CRISPR spacers at regular occurring sets of time, however when a signal was detected the bacteria would insert a signal sequence instead.  This locus can then be read using pre-existing sequencing tools providing a readout of events.  The researchers hope this technology could be used to record biological events.

CRISPR May Not Revolutionize Mitochondrial Genome Editing

Gammage, P.A.  et. al. (2017) Trends in Genetics.

Mitochondrial DNA has increased in prominence in both biology and medicine as a major player for various diseases.  Attempts to alter the genetic information of mitochondria have made significant advances using zinc finger and TALEN nucleases.  These protein only nucleases are easily delivered into the mitochondria through existing machinery.  While CRISPR has revolutionized genome editing, it is struggling in mitochondria due to the lack of an endogenous mechanism for nucleic acid transport into the mitochondria, preventing its adoption.

Increasing the Potency of T Cell Cancer Therapy

GEN News Highlights, 21 November 2017,

In the United Kingdom, Cardiff University researchers have used CRISPR to create T cells up to a thousand times more sensitive to cancer cells.  These cells have been edited to remove their own T-cell receptors, leaving only those targeting cancer cells.  The hope is that custom immunotherapies such as this may one day replace conventional cancer therapies.

Are Gene Drives Too Risky?

Carl Zimmer, The New York Times, 16 Nov 2017.

Kevin Esvelt of Harvard University was one of the first to put forth the idea of using gene drives to save endangered wildlife from extinction by reducing/eliminating invasive animals.  Now Dr. Esvelt has published a new article on bioRxiv in which he presents mathematical models that describe what could happen after the release of a gene drive, even for field trials.  These models detail what Dr. Esvelt is calling an unacceptable risk of the altered genes spreading to locations where the targeted species is not invasive.  The authors were careful to emphasize that disease eliminating gene drives, such as those proposed to eliminate malaria, should still be considered as this would allow the rapid elimination of disease carrying vectors across wide areas.

Gene Drives Could Aid New Zealand’s War on Rats

Ed Yong, The Atlantic, 16 Nov 2017.

Invasive predators have long been devastating to New Zealand’s native birds, notably the flightless giant kakapo parrot and kiwi .  Through Predator-Free 2050, New Zealand is aiming to eliminate invasive rats, possums, and stoats.  One possible mechanisms may be a CRISPR gene drive that allows rapid proliferation of detrimental genes through a population without harming other animals like traditional pesticide methods.

New Cas9 Cryo-EM Structure Solved

Huai, C. et. al. (2017) Nature Communications. 8:1375.

Researchers have solved a 5.2 Å cryo-EM structure of Cas9 complexed with sgRNA and target DNA.  The structure found that the HNH domain moves closer to the DNA than previously reported and suggests that this new structure resembles a DNA cleavage-activating structure of Cas9.

Automated Screening for CRISPR Mutations

Steve Siembieda and Kyle Luttgeharm, GEN Tutorials, 1 Nov 2017.

Screening for CRISPR edits remains a large bottleneck in the gene editing process.  This GEN tutorial walks through a novel method for simultaneously identifying clones containing edits, while predicting the zygosity of the mutation in diploid organisms.  The assay relies on statistical models that predict the frequency of heteroduplex formation versus duplex formation and a T7 Endonuclease I based cleavage assay coupled with the quantitative abilities of capillary electrophoresis.

Identification of a Thermostable Cas9

Harrington L.B. et. al. (2017) Nature Communications 8:1424.

The CRISPR/Cas systems used for genome editing to date have come from mesophilic bacteria, preferring temperatures of 20-45°C, preventing their use at higher temperatures.  Harrington et. al. have identified a Cas9 protein from the thermophilic bacterium Geobacillus stearothermophilus (GeoCas9) that is active in temperature up to 70°C, providing a much wider range of possibilities.  Additionally, GeoCas9 showed greater stability as an RNP complex in human plasma, opening the door to possible therapeutic uses.

First License Granted for New CRISPR Systems

Alex Philippidis, GEN News Highlights, 13 November 2017,

Excision BioTherapeutics is the first to exclusively license the new CRISPR systems discovered by Jennifer Doudna’s group in 2016.  These new CRISPR systems were found in uncultivated microbes and are significantly smaller than Cas9, allowing for easier delivery into target cells.  These new CRISPR/Cas proteins do not interfere with the ongoing patent battle between UC-Berkeley and The Broad Institute, allowing for a much simpler patent landscape.

How Easy is CRISPR Technology, Really?

Annie Sneed, Scientific American, 02 November 2017,

Almost every CRISPR article describes its ease of use. With DIY CRISPR kits available by mail, one reporter set out to determine how easy CRISPR really is.  In this article, published by Scientific American, Annie Sneed attempts CRISPR in her kitchen, a community lab in Santa Clara, and finally meets with a professional scientist from the University of California-Berkeley in order to determine just how easy gene editing really is.