Exon 10 was replaced with an FRT-flanked neo cassette with a 5' loxP site and a modified exon 10 in which nucleotide substitutions result in the amino acid substitution of alanine for threonine at position 649 (T649A) followed by a loxP site. Flp-mediate recombination removed the neo cassette. Cre-mediated recombination removed the modified exon 10. Western blot analysis confirmed the absence of protein expression in the soleus, gastrocnemius, tibialis anterior, adipose and heart. (J:194026)