This allele is a derivative of Pitx2tm2Jfm targeted allele. An IRES-lacZ cassette followed by a loxP-flanked neomycin resistance cassette replaced a genomic fragment containing the coding region of exon 2 and all of exon 3. This allele encodes the heart- and lung-specific c isoform in the absence of the a and b isoforms. The neomycin resistance cassette was removed via Cre-mediated recombination.