Abstract
Selfish genes are DNA elements that increase their rate of genetic transmission at the expense of other genes in the genome and can therefore quickly spread within a population. It has been suggested that selfish elements could be exploited to modify the genome of entire populations for medical and ecological applications. Here we report that transcription activator-like effector nuclease (TALEN) and zinc finger nuclease (ZFN) can be engineered into site-specific synthetic selfish elements (SSEs) and demonstrate their transmission of up to 70% in the Drosophila germline. We show here that SSEs can spread via DNA break-induced homologous recombination, a process known as ‘homing’ similar to that observed for homing endonuclease genes (HEGs), despite their fundamentally different modes of DNA binding and cleavage. We observed that TALEN and ZFN have a reduced capability of secondary homing compared to HEG as their repetitive structure had a negative effect on their genetic stability. The modular architecture of ZFNs and TALENs allows for the rapid design of novel SSEs against specific genomic sequences making them potentially suitable for the genetic engineering of wild-type populations of animals and plants, in applications such as gene replacement or population suppression of pest species.
Highlights
Selfish genes are DNA elements that have evolved to enhance their own transmission relative to the rest of the genome
We designed a reporter system in Drosophila to monitor the ability of zinc finger nuclease (ZFN)-AAVS1 [11] and PPP1R12C transcription activator-like effector nuclease (TALEN)-R [15] to invade a target sequence by homing
Taken together our results provide a proof of principle that both TALEN and ZFN nucleases can be adapted to generate selfish elements (SSEs) that can spread into the genome of naive host populations with modalities similar to those described for homing endonuclease genes (HEGs)
Summary
Selfish genes are DNA elements that have evolved to enhance their own transmission relative to the rest of the genome. Occurring selfish elements include transposable elements, meiotic drive chromosomes, sex ratio distorting elements and homing endonuclease genes (HEGs). HEGs are highly specific endonucleases that generate double-strand breaks (DSB) at specific loci in the host genome [2]. The recognition sequence is usually 14–40 bp long and occurs generally only once in the host haploid genome. HEGs cleave the target sequence and the broken chromosome can activate the recombinational repair machinery of the cell, which uses the homologous HEG-containing allele as a corrective template. If homing occurs in the germ cells, HEGs are transmitted to the progeny at a frequency higher than the expected Mendelian ratio, and can spread within a host population
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