A loxP site was inserted upstream of exon 1. A neo cassette with a 3' loxP site was inserted downstream of exon 1. Cre mediated recombination removed the neo cassette. QRT-PCR confirmed the absence of the standard transcript in the liver, heart, lung, kidney, muscle, brain and bone (with or without marrow) and the absence of the alternative transcript in the liver, heart, lung, kidney, muscle and brain but not bone (with or without marrow).