In an April 2016 commentary in Nature, a genetically modified mushroom, created by Yinong Yang, a scientist at Pennsylvania State University, was reported in which had bypassed regulation from the US Department of Agriculture. The modification deletes part of a gene in the polyphenol oxidase (PPO) family, which is responsible for the mushrooms going brown. The edited mushrooms can then be left on the supermarket shelf longer without going off.
This loophole was due to the type of gene editing being performed, which used the CRISPR/Cas9 approach to knock out the gene. Because no foreign DNA was detected at the editing site, it was considered not applicable for regulation.
Now, a new correspondence in Nature Biotechnology from Jungeun Kim & Jin-Soo Kim from the Seoul National University, has questioned this decision. They argue that because the gene editing was performed using a plasmiddelivery system (a small circular piece of DNA that can be used to introduce the tools needed for the editing to the cells), which does contain foreign DNA, then that plasmid could fragment and incorporate into the mushroom's genome at other, unpredictable sites.
They therefore recommend that full genome sequencing is performed on any new or future GM crop strain to ensure that no foreign DNA sequences are present in any locations. Whether this recommendation is pursued by the USDA remains to be seen.
In terms of GM food created by CRISPR/Cas9 gene editing, we are just at the very start of a very big wave. Hopefully lessons have been learned from the PR disaster of the original introduction of GMOs during the 1990s, and proper legislation, regulation and ways to increase public awareness and acceptance will soon be in place.
--- Ed Ryder
 Waltz, E. (2016). Gene-edited CRISPR mushroom escapes US regulation. Nature, 532(7599), 293. https://doi.org/10.1038/nature.2016.19754
 Kim, J., & Kim, J.-S. (2016). Bypassing GMO regulations with CRISPR gene editing. Nature Biotechnology, 34(10), 1014–1015. https://doi.org/10.1038/nbt.3680