The allele contains two knock-in sequences incorporated by two rounds of homologous recombineering. The floxed target I sequence is inserted between exon IX and exon X; it is composed of a loxP site, a mouse engrailed 2 splice acceptor sequence, a destabilization domain (DD), a 2xPolyA transcriptional STOP sequence, a neo cassette and a second loxP site.
Target II sequence is inserted in place of the Il1r1 stop codon in exon XI; it is composed of 3 hemagglutinin tags (3xHA), a STOP codon fluorescent protein, an internal ribosome entry site (IRES), a tdTomato fluorescent protein sequence, a single FRT site and a STOP codon. Mice containing target I do not produce a functional protein.