An FRT and loxP flanked neo cassette was inserted upstream of exon 11. An additionally loxP site was inserted downstream of exon 13. Enzymatic assay confirmed less than 10% normal activity levels. Flp-mediated recombination removed the neo cassette and left exons 11 through 13 floxed. Cre mediated excision then removed exons 11 through 13. (J:94077, J:184908)