The dawn of active genetics

Abstract

On December 18, 2014, a yellow female fly quietly emerged from her pupal case. What made her unique was that she had only one parent carrying a mutant allele of this classic recessive locus. Then, one generation later, after mating with a wild-type male, all her offspring displayed the same recessive yellow phenotype. Further analysis of other such yellow females revealed that the construct causing the mutation was converting the opposing chromosome with 95% efficiency. These simple results, seen also in mosquitoes and yeast, open the door to a new era of genetics wherein the laws of traditional Mendelian inheritance can be bypassed for a broad variety of purposes. Here, we consider the implications of this fundamentally new form of “active genetics”, its applications for gene-drives, reversal and amplification strategies, its potential for contributing to cell and gene therapy strategies, and ethical/biosafety considerations associated with such active genetic elements.

Multidimensional chemical control of CRISPR–Cas9

“…For example, Cas9 enables facile genomic alterations, as well as robust self-propagation of such alterations throughout a species population via gene drives 3 . Furthermore, catalytically inactive Cas9 (dCas9) can be fused to a wide range of effectors, such as fluorescent proteins for genome imaging 4 , enzymes that modify DNA or histones for epigenome editing 5 , and transcription-regulating domains for controlling endogenous gene expression 6 .…”

“…Such systems would enable regulated and specific genome editing. Temporal control of nuclease activity may also have uses in emerging technologies, including gene drives 3,21 . Consistent with our observations for dSpCas9.VP64 (Supplementary Fig.…”

Spatial gene drives and pushed genetic waves

“…11, 2017; 2 The development of the CRISPR/Cas9 system [1][2][3][4], derived from an adaptive immune system in prokaryotes [5], has received much recent attention, in part due to its exceptional versatility as a gene editor in sexually-reproducing organisms, compared to similar exploitations of homologous recombination such as zinc-finger nucleases (ZFNs) and the TALENS system [4,6]. Part of the appeal is the potential for introducing a novel gene into a population, allowing control of highly pesticide-resistant crop pests and disease vectors such as mosquitoes [7][8][9][10]. Although the genetic modifications typically introduce a fitness cost or a "selective disadvantage", the non-Mendelian population genetics embodied in CRISPR/Cas9 gene drives nevertheless allows edited genes to spread, even when the fitness cost of the inserted gene is large.…”

“…Part of the appeal is the potential for introducing a novel gene into a population, allowing control of highly pesticide-resistant crop pests and disease vectors such as mosquitoes [7][8][9][10]. Although the genetic modifications typically introduce a fitness cost or a "selective disadvantage", the non-Mendelian population genetics embodied in CRISPR/Cas9 gene drives nevertheless allows edited genes to spread, even when the fitness cost of the inserted gene is large.…”

Autocatalytic–Protection for an Unknown Locus CRISPR–Cas Countermeasure for Undesired Mutagenic Chain Reactions

“…The driven gene is inherited by each generation, through HDR, with a probability 'h' of approximately 0.95<h<1.0. Non-homologous end joining (NHEJ), can lead to an evolvedresistant allele to the homing endonuclease 6,10 . Because NHEJ occurs at a non-zero probability, 1-h, at each generation, the gene drive will lose its ability to spread in a population over some number of generations.…”