Biology subjects

Simon L Bullock

Publications and source records attributed to Simon L Bullock.

3 recordsLinked to original sources

bioRxiv2016

Expansion of the CRISPR toolbox in an animal with tRNA-flanked Cas9 and Cpf1 gRNAs

We present vectors for producing multiple CRISPR gRNAs from a single RNA polymerase II or III transcript in Drosophila. The system, which is based on liberation of gRNAs by processing of flanking t {dagger}RNAs, permits highly efficient multiplexing of Cas9-based mutagenesis. We also demonstrate that the {dagger}RNA-gRNA system markedly increases the efficacy of conditional gene disruption by Cas9 and can promote editing by the recently discovered RNA-guided endonuclease Cpf1.

Genetics↗

bioRxiv2015

CRISPR with independent transgenes is a safe and robust alternative to autonomous gene drives in basic research

CRISPR/Cas technology allows rapid, site-specific genome modification in a wide variety of organisms. CRISPR components produced by integrated transgenes have been shown to mutagenise some genomic target sites in Drosophila melanogaster with high efficiency, but whether this is a general feature of this system remains unknown. Here, we systematically evaluate available CRISPR/Cas reagents and experimental designs in Drosophila. Our findings allow evidence-based choices of Cas9 sources and strategies for generating knock-in alleles. We perform gene editing at a large number of target sites using a highly active Cas9 line and a collection of transgenic gRNA strains. The vast majority of target sites can be mutated with remarkable efficiency using these tools. We contrast our method to recently developed autonomous gene drive technology for genome engineering (Gantz & Bier, 2015) and conclude that optimised CRISPR with independent transgenes is as efficient, more versatile and does not represent a biosafety risk.

Genetics↗

bioRxiv2014

An optimized CRISPR/Cas toolbox for efficient germline and somatic genome engineering in Drosophila

The type II CRISPR/Cas system has recently emerged as a powerful method to manipulate the genomes of various organisms. Here, we report a novel toolbox for high efficiency genome engineering of Drosophila melanogaster consisting of transgenic Cas9 lines and versatile guide RNA (gRNA) expression plasmids. Systematic evaluation reveals Cas9 lines with ubiquitous or germline restricted patterns of activity. We also demonstrate differential activity of the same gRNA expressed from different U6 snRNA promoters, with the previously untested U6:3 promoter giving the most potent effect. Choosing an appropriate combination of Cas9 and gRNA allows targeting of essential and non-essential genes with transmission rates ranging from 25% - 100%. We also provide evidence that our optimized CRISPR/Cas tools can be used for offset nicking-based mutagenesis and, in combination with oligonucleotide donors, to precisely edit the genome by homologous recombination with efficiencies that do not require the use of visible markers. Lastly, we demonstrate a novel application of CRISPR/Cas-mediated technology in revealing loss-of-function phenotypes in somatic cells following efficient biallelic targeting by Cas9 expressed in a ubiquitous or tissue-restricted manner. In summary, our CRISPR/Cas tools will facilitate the rapid evaluation of mutant phenotypes of specific genes and the precise modification of the genome with single nucleotide precision. Our results also pave the way for high throughput genetic screening with CRISPR/Cas.

Genetics↗