CRISPR/cas9 endonuclease-mediated genome editing is used to insert a double stop codon (TGATGA) downstream of the initator ATG in in exon 2. The sgRNA (GGAACACAGGGCCAGTTGA(GGG), and ssODN donor (CAGTCTCGTGAATGAGCTTTCTTCTTCCAGGTTCCGATTCAATGCAAAGAACACAGGGCCTCACTAGGGTGTCT CTGTTTCTTGGCTTTGTAAAGGTG) were used. (J:101977)