CRISPR/Cas9 mutagenesis was used to insert two loxP sites, one 397 bp upstream of exon 2 and a second 309 bp dpwnstream of exon 2. Cre-mediated recombination deleted exon 2, resulting in a frameshift mutation before the TM1 domain and creating a null allele. qPCR analysis confirmed the absence of mRNA expression in homozygous mutant brains. (J:273611)