A snRNA:U6:96Ac promoter drives expression of six sgRNAs; two (CCTCATGGACGAAAGCAAGG and ATTGATGAGCGGGAACGCGG) target Snap24 for knockout, two (CTCGGTCTTCGGGACCTGAG and GTAGCCCTTGATGATCAAGG) target Snap25 for knockout and two (GATGGATGACGATGACGAAG and TCTGCTCTACGAAACCCAGG) target Snap29 for knockout. The sgRNAs are expressed as a polycistronic cassette based on the tRNA-gRNA design of FBrf0233589.