Edgington Matthew P, Harvey-Samuel Tim, Alphey Luke
The Pirbright Institute Woking UK.
Evol Appl. 2020 Mar 25;13(8):1939-1948. doi: 10.1111/eva.12945. eCollection 2020 Sep.
CRISPR-based gene drives bias inheritance in their favour by inducing double-stranded breaks (DSBs) at wild-type homologous loci and using the drive transgene as a repair template-converting drive heterozygotes into homozygotes. Recent studies have shown that alternate end-joining repair mechanisms produce cut-resistant alleles that rapidly induce drive failure. Multiplexing-simultaneously targeting multiple sites at the wild-type locus-is commonly assumed to overcome this issue since resistance would need to develop at all target sites for the system to fail. This may work for some population suppression drives targeting essential (e.g. viability or fertility) genes if careful design can ensure cut-resistant alleles themselves have low fitness. However, here, models are used to demonstrate that this approach will be ineffective when targeting neutral loci. We then go on to compare the performance of four alternative population-level multiplexing approaches with standard individual-level multiplexing. Two of these approaches have mechanisms preventing them from becoming linked, thus avoiding multiple simultaneous DSBs and giving a large improvement. Releasing multiple unlinked drives gives a modest improvement, while releasing multiple drives that may become linked over time produces a decrease in performance under the conditions tested here. Based on performance and technical feasibility, we then take one approach forward for further investigation, demonstrating its robustness to different performance parameters and its potential for controlling very large target populations.
基于CRISPR的基因驱动通过在野生型同源位点诱导双链断裂（DSB）并使用驱动转基因作为修复模板，将驱动杂合子转化为纯合子，从而使遗传偏向于自身。最近的研究表明，替代末端连接修复机制会产生抗切割等位基因，从而迅速导致驱动失败。通常认为多重靶向——同时在野生型位点靶向多个位点——可以克服这个问题，因为系统要失败的话，抗性需要在所有靶位点都出现。如果精心设计能够确保抗切割等位基因本身适应性较低，那么对于一些针对必需（如生存力或繁殖力）基因的种群抑制驱动来说，这种方法可能有效。然而，本文通过模型证明，当靶向中性位点时，这种方法将无效。然后，我们继续比较四种替代的种群水平多重靶向方法与标准个体水平多重靶向方法的性能。其中两种方法具有防止它们连锁的机制，从而避免多个同时发生的DSB，并带来大幅改进。释放多个不连锁的驱动会有适度改进，而释放多个可能随时间连锁的驱动，在此处测试的条件下会导致性能下降。基于性能和技术可行性，我们进而推进一种方法以供进一步研究，证明其对不同性能参数的稳健性及其控制非常大的目标种群的潜力。
