Unexpected insertion of carrier DNA sequences into the fission yeast genome during CRISPR-Cas9 mediated gene deletion.

None of the four microprotein-encoding genes was essential for viability, meiosis or sporulation, and the deletion cells were no more sensitive to a range of cell stressors than wild-type, leaving the function of the proteins unresolved. During CRISPR-Cas9 editing however, a number of strains were isolated in which additional sequences were inserted into the target loci at the Cas9 cut site. Sequencing of the inserts revealed these to be derived from the chum salmon Oncorhynchus keta, the source of the carrier DNA used in the S. pombe transformation.