(A) Schematic diagram of IrxA cluster, Irx1 allele, targeting construct and recombinant allele. The targeting construct carries a LacZ reporter gene and a neomycin resistance gene (Neo). The entire Irx1 sequence from start codon to stop codon is replaced by LacZ-Neo in Irx1 knockout mice. Probes position shows the sites of primers for genotyping. (B) RT-PCR result of Irx1 genotyping strategy. Irx1+/+ mice only have a 106 bp WT band, Irx1−/− mice only have a 400 bp LacZ band, Irx1+/− mice have both of the bands. (C) qRT-PCR analysis of Irx1 mRNA level in P0 Irx1+/+ and Irx1−/− lung tissue. (D) Western blot result shows Irx1 protein is ablated in Irx1−/− lung tissue. ***, p < 0.001.