Gold Nanoparticles Deliver CRISPR in Muscular Dystrophy Treatment

Sophia Ktori, GEN News Highlights, 04 October 2017, http://www.genengnews.com/gen-news-highlights/crispr-nanoparticles-repair-duchenne-muscular-dystrophy-gene/81255009

Scientists working on CRISPR delivery have developed a gold nanoparticle that encapsulates the CRISPR/Cas machinery for delivery to cells.  This new technique, coined CRISPR-Gold, was published in Nature Biomedical Engineering (https://www.nature.com/articles/s41551-017-0137-2).  In the paper the authors demonstrated CRISPR-Gold’s ability to correct the mutated dystrophin gene in a mouse model, with mice receiving CRISPR-Gold treatment displaying two-fold improvement in hanging time in a four-limb hanging test, compared to control mice.

Chinese Research Team Fix Genetic Disorder in Human Embryos

David Cyranoski, 02 October 2017, Nature News, http://www.nature.com/news/chinese-scientists-fix-genetic-disorder-in-cloned-human-embryos-1.22694

A new report in Protein and Cell (https://www.ncbi.nlm.nih.gov/pubmed/28942539) is the latest in a string of human embryo CRISPR publications.  Using a modified CRISPR/Cas9 system tethered to a second enzyme that can swap individual DNA bases, the researchers targeted an A to G point mutation that results in β-thalassemia.  Eight of the 20 cloned embryos contained a corrected copy of the gene, possibly curing the recessive disorder.  The scientists were careful to point out that not all cells in the embryo were modified, which could have unintended consequences.

New Cas9 Mutations Increase Accuracy

Chen et. al. (2017) Nature. https://www.ncbi.nlm.nih.gov/pubmed/28931002

Researchers using FRET to study previously engineered high-fidelity Cas9 (SpCas9-HF1) and enhanced Cas9 (eSpCas9), identified that these versions are trapped in an inactive state when bound to off-target sites.  Using this observation and rational protein engineering, the researchers made additional modifications to the REC3 domain to prevent activation of the HNH nuclease domain unless the guide RNA and target DNA match is very close.  This new Cas9, coined Hyper Cas9 (HypaCas9) maintains the native Cas9 on target efficiency, but decreases the number of off-target events.

CRISPR Allows for Target Mapping in Rare Cancers

Sharifnia, T., et. al. (2017) Cell Chemical Biology. 24:1075-1091. https://www.ncbi.nlm.nih.gov/pubmed/28938087

Rare cancers have traditionally been difficult to study due to low incidence and limited sample availability.  However, new technologies, such as sequencing, have allowed for a greater understanding of the underlying genetic causes.  In tandem with sequencing technologies, CRISPR/Cas and small molecule screens have allowed researchers to rapidly screen rare cancers for possible mechanisms and treatments.

CRISPR Reveals How Butterflies Get Their Color

Rachael Lallensack, Nature News, 18 September 2017, http://www.nature.com/news/crispr-reveals-genetic-master-switches-behind-butterfly-wing-patterns-1.22628

Two new studies in the Proceedings of the National Academy of Sciences (http://www.pnas.org/content/early/2017/08/29/1709058114, http://www.pnas.org/content/early/2017/08/29/1708149114) provide insight into butterfly wing color.  The studies identified two genes, WntA is responsible for creation of the coloring pattern and borders, while optix fills the color within the borders.  Understanding butterfly coloration could provide insights into adaptations such as mimicry.

Reversing CRISPR Gene Drives

Vella, M.R. et. al. (2017) Scientific Reports 7:11038. https://www.ncbi.nlm.nih.gov/pubmed/28887462

CRISPR/Cas gene drives could be used to eliminate vector-borne diseases such as malaria and Lyme disease. However, release of modified organisms is controversial in part due to unforeseen consequences.  Developing strategies for gene drive reversal could prove useful if such problems arise.  This paper develops models to evaluate the effectiveness of gene drive counter-measures in order to evaluate their potential use.

Could CRISPR be Used as Antimicrobials?

Bikard, D., Barrangou, R., (2017) Current Opinion in Microbiology, 37:155-160. https://www.ncbi.nlm.nih.gov/pubmed/28888103

Self-targeting bacteria with CRISPR usually proves fatal.  This observation could lead to a new type of antimicrobial where the CRISPR/Cas system is introduced to fight infection.  This review discusses how CRISPR/Cas could target bacterial infections, as well as how the system may be delivered to the infection site.

dCas9 Pull Down Isolates Chromatin Cis Factors

Liu, X., et. al. (2017) Cell 170:1028-1043. https://www.ncbi.nlm.nih.gov/pubmed/28841410

Many genes are regulated by cis-regulatory elements, though the molecular composition of these elements remains unknown.  In a new study published in Cell, Liu et. al. describe a new technique called CAPTURE (CRISPR affinity purification in situ of regulatory elements) that uses a biotin labeled dCas9 to isolate cis regulatory elements in an unbiased fashion, allowing for insights into genome structure and function.

Doubts Raised About Human Embryo Editing Paper

Dieter et. al. (2017) BioRxiv, 181255. http://www.biorxiv.org/content/early/2017/08/28/181255

On 02 August 2017, a Nature article claimed a major breakthrough in CRISPR genome editing.  Researchers from around the world, including the United States, announced that they had successfully corrected viable human embryos heterozygous for the MYBPC3 mutation that results in heart disease, without mosaicism.  Recently, the results of this article have been called into question with the publishing of a BioRxiv article.  The authors of the new paper identify other possible mechanisms that could have caused the observed results and suggest additional experiments to effectively prove CRISPR gene editing.

A Quick Guide to Generating CRISPR Modified Mice

Huijbers I.J. (2017) Methods Mol Biol 1642:1-19 https://www.ncbi.nlm.nih.gov/pubmed/28815490

Attempting CRISPR gene editing for the first time can be a daunting task.  While much simpler than previous gene editing technologies, there are still many methods that must be compared.  This review seeks to answer essential questions that may arise during the generation of CRISPR modified mice, covering the latest in cell culture and gene editing tools.