Whitelaw, C. B. A. | Search bioRxiv

bioRxiv2020

Novel combination of CRISPR-based gene drives eliminates resistance and localises spread

Invasive species are among the major driving forces behind biodiversity loss. Gene drive technology may offer a humane, efficient and cost-effective method of control. For safe and effective deployment it is vital that a gene drive is both self-limiting and can overcome evolutionary resistance. We present HD-ClvR, a novel combination of CRISPR-based gene drives that eliminates resistance and localises spread. As a case study, we model HD-ClvR in the grey squirrel (Sciurus carolinensis), which is an invasive pest in the UK and responsible for both biodiversity and economic losses. HD-ClvR combats resistance allele formation by combining a homing gene drive with a cleave-and-rescue gene drive. The inclusion of a self-limiting daisyfield gene drive allows for controllable localisation based on animal supplementation. We use both randomly mating and spatial models to simulate this strategy. Our findings show that HD-ClvR can effectively control a targeted grey squirrel population, with little risk to other populations. HD-ClvR offers an efficient, self-limiting and controllable gene drive for managing invasive pests.

genetics↗

bioRxiv2020

Severe perinatal hydrops fetalis in genome edited pigs with a biallelic five base pair deletion of the Marfan syndrome gene, FBN1

This paper describes a genome editing project using CRISPR-Cas9. The objective was to create a large animal model of human Marfan syndrome by targeting the FBN1 gene of the pig, Sus scrofa, using a single guide and non-homologous end joining which was expected to create short insertion or deletion mutations at the 5 end of the gene. The editing successfully created a five base pair deletion in exon 2 of FBN1, which was homozygous in two animals. However, the phenotype of these piglets was unexpected, since they showed none of the signs consistent with Marfan syndrome but both suffered extreme hydrops fetalis with a large amount of fluid located under the skin and in the abdomen. One of the edited piglets was stillborn and the other was euthanised at birth on welfare grounds. It is likely that this result was due to unanticipated on- or off-target mutations, possibly in the GLDN gene 3 megabases away from FBN1. This result provides more evidence for unexpected outcomes of CRISPR- Cas9 gene editing and supports the proposal that all genome edited individuals should be subjected to strategies to track the CRISPR footprint, such as whole genome sequencing, before being used for further experimentation or in clinical applications.

molecular biology↗