Exploiting a Y chromosome-linked Cas9 for sex selection and gene drive

Stephanie Gamez,Ting Yang,Héctor M Sánchez C,Nikolay P Kandul,Omar S Akbari,Jared B Bennett,Jonny E Duque,John M Marshall,Duverney Chaverra-Rodriguez,Igor Antoshechkin,Anna Buchman,Stelia C Mendez-Sanchez,Philippos A Papathanos

doi:10.1038/s41467-021-27333-1

Abstract

CRISPR-based genetic engineering tools aimed to bias sex ratios, or drive effector genes into animal populations, often integrate the transgenes into autosomal chromosomes. However, in species with heterogametic sex chromsomes (e.g. XY, ZW), sex linkage of endonucleases could be beneficial to drive the expression in a sex-specific manner to produce genetic sexing systems, sex ratio distorters, or even sex-specific gene drives, for example. To explore this possibility, here we develop a transgenic line of Drosophila melanogaster expressing Cas9 from the Y chromosome. We functionally characterize the utility of this strain for both sex selection and gene drive finding it to be quite effective. To explore its utility for population control, we built mathematical models illustrating its dynamics as compared to other state-of-the-art systems designed for both population modification and suppression. Taken together, our results contribute to the development of current CRISPR genetic control tools and demonstrate the utility of using sex-linked Cas9 strains for genetic control of animals.

Highlights

CRISPR-based genetic engineering tools aimed to bias sex ratios, or drive effector genes into animal populations, often integrate the transgenes into autosomal chromosomes
One such proposed strategy involves the insertion of CRISPR elements on the ♂-specific Y chromosome to restrict activity exclusively to ♂’s, which can be beneficial, for example, for engineering gene drives with limited persistence or invasiveness[17], or for limiting undesired activity in the maternal germline that can adversely affect the spread of gene drives by generating functional resistant alleles in the female germline[2,18,19,20,21]
We evaluate its ability to function as a high-throughput reliable sex selection tool which we term SEx LinkEd CRISPR selecTion (SELECT) and as a gene drive using a previously described system termed HomeR26

Summary

Introduction

CRISPR-based genetic engineering tools aimed to bias sex ratios, or drive effector genes into animal populations, often integrate the transgenes into autosomal chromosomes. Since sex bias is important for insect control and the rules governing sex chromosome inheritance are widely conserved (for example, an XY sex-determination system), linkage or targeting of CRISPR activity to sex chromosomes can be advantageous for engineering specific types of genetic control mechanisms including gene drives[15,16,17] One such proposed strategy involves the insertion of CRISPR elements on the ♂-specific Y chromosome to restrict activity exclusively to ♂’s, which can be beneficial, for example, for engineering gene drives with limited persistence or invasiveness[17], or for limiting undesired activity in the maternal germline that can adversely affect the spread of gene drives by generating functional resistant alleles in the female germline[2,18,19,20,21]. In the case of postzygotic elimination of daughters, a strategy called CRISPR-based X-poisoning could result in a control method that remains non-invasive but is more persistent than other self-limiting strategies[17]

Methods

Results

Conclusion