A fly model establishes distinct mechanisms for synthetic CRISPR/Cas9 sex distorters

by Barbara Fasulo, Angela Meccariello, Maya Morgan, Carl Borufka, Philippos Aris Papathanos, Nikolai Windbichler Synthetic sex distorters have recently been developed in the malaria mosquito, relying on endonucleases that target the X-chromosome during spermatogenesis. Although inspired by naturally-occurring traits, it has remained unclear how they function and, given their potential for genetic control, ho w portable this strategy is across species. We establishedDrosophila models for two distinct mechanisms for CRISPR/Cas9 sex-ratio distortion —“X-shredding” and “X-poisoning”—and dissected their target-site requirements and repair dynamics. X-shredding resulted in sex distortion when Cas9 endonuclease activity occurred during the meiotic stages of spermatogenesis but not when Cas9 was expressed from the stem cell stages onward s. Our results suggest that X-shredding is counteracted by the NHEJ DNA repair pathway and can operate on a single repeat cluster of non-essential sequences, although the targeting of a number of such repeats had no effect on the sex ratio. X-poisoning by contrast, i.e. targeting putative haploletha l genes on the X chromosome, induced a high bias towards males (>92%) when we directed Cas9 cleavage to the X-linked ribosomal target geneRpS6. In the case of X-poisoning sex distortion was coupled to a loss in reproductive output, although a dominant-negative effect appeared to drive the mechanism of female lethality. These model systems wil...
Source: PLoS Genetics - Category: Genetics & Stem Cells Authors: Source Type: research