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Every few months we highlight a subset of the new plasmids in the repository through our hot plasmids articles. These articles provide brief summaries of recent plasmid deposits and we hope they'll make it easier for you to find and use the plasmids you need. If you'd ever like to write about a recent plasmid deposit please sign up here.

Genome-wide CRISPR/Cas9 screens are a high-throughput systematic approach for identifying genes involved in a biological process. These screens provide an alternative to genome-wide RNAi screens, which although highly effective, are affected by low on-target efficacy, non-specific toxicity, and off-target effects. The flaws of RNAi screens are well characterized and strategies exist to control for these faults. However, it’s still unclear if similar pitfalls exist for CRISPR screens and how best to design these screens to controls for flaws. Recently the Bassik Lab at Stanford developed a new genome-wide CRISPR knockout screen to analyze the following unanswered questions about CRISPR screen design.

Have you ever wondered how long it takes to make a plasmid? Or have you thought about how much total time you spend in the lab cloning before you can start on your experiment? What about all the reagents you need to order? Sometimes, it feels like an eternity of cloning, waiting, and repeating before you can finally dive deep into experiments.

Since one million plasmids shared is upon us at Addgene, we started wondering, just how much time and money do researchers spend cloning? How much does material sharing speed science?

CRISPR has greatly enhanced the ability of scientists to make genomic alterations, bringing about a revolution in genome engineering, with new techniques rapidly being developed. Performing a CRISPR experiment requires delivery of, at minimum, two components: the Cas9 protein and a guide RNA (gRNA) targeting your genomic site of interest. This is commonly performed by transfecting cells with a plasmid, such as PX459, which encodes Cas9 and contains a site for inserting a custom gRNA.  While this methodology has proven to be incredibly valuable to scientists, there are some potential complications that must be considered when using this method:

1.     Cells must be amenable to transfection or viral transduction
2.     Appropriate promoters must be chosen for both Cas9 and gRNA expression  
3.     Plasmid DNA may be incorporated into the genome
4.     Off-target effects can occur due to prolonged Cas9 expression
5.     The requirement for Cas9 transcription and translation delays editing

In this episode of the Addgene Podcast, we introduce you to the Journal of Emerging Investigators, an open-access journal that enables high school students to publish peer-reviewed scientific research. You’ll meet some of the folks behind the journal and hear from a fantastic team of high school students who recently submitted to the journal with funding from Addgene.