Two point mutations, chr6:31197455G>A and chr6:31197457A>T (GRCm39), were created using an sgRNA and an ssODN template with CRISPR/Cas9 technology. The mutations in intron 1 eliminate the exon 1 splice donor site, changing it from from G-GTA to G-ATT, which virtually eliminates transcript expression from this allele.