ES cells were mutagenized using ethyl methansulfonate (EMS), leading to a C-to-T nonsense mutation (GRCm39:chr14:g.55857155C>T) that changes glutamine codon 155 (CAG) in exon 6 (out of 20) to a stop codon (TAG) (p.Q155*). RT-PCR of testes samples from mutants confirmed the lack of transcripts from this allele. (J:94208)