Three consecutive TEV protease recognition sites with a novel BamHI restriction site were inserted
between P475 and P476 of exon 11. At the stop codon an additional BamHI was inserted as well as a C-terminal c-Myc epitope tag with a stop codon. A floxed puro cassette was inserted downstream of exon 12. Cre mediated recombination removed the puro cassette.