A vector containing a loxM site, loxP site, sequence coding for exon 2 with an HA epitope tag (YPYDVPDYASL) inserted after Q41 in inverse orientation, a loxM site, a pgk-neo cassette, sequence encoding exon 2 and a final loxP site was inserted via homologous recombination. Cre-mediated recombination deletes the pgk-neo cassette and wild-type exon 2 and inverts the HA tagged exon 2. The resulting allele contains a loxM site HA tagged exon 2 and a loxP site. (J:229237)