A floxed neo cassette was inserted in intron 20 and point mutations disrupting the PDZ-binding motif were inserted in exon 21 via homologous recombination. Cre mediated recombination removed the neo cassette. Western blot analysis detected no difference in expression levels compared to the wild-type protein. Co-immunoprecipitation assays confirmed the loss of association between the mutant protein and Dlg4. This modification disrupts the function of the alpha 1 isoform while leaving expression of the other isoforms intact. (J:338643)