Ctsl^tm1.2Thre

Exon 2 was replaced with a modified exon 2 in which in which the conventional start codon M1 ATG was substituted by TTC. A floxed polyadenylation (STOP) sequence was inserted downstream of the modified exon 2. Flp-mediated recombination removed the FRT-flanked puromycin resistance cassette inserted into intron 2. Cre-mediated recombination removed the floxed polyadenylation sequence and allowed for expression from a transcription initiation site in exon 3. Western blot analysis confirmed the absence of protein expression in kidney, liver and heart lysates from homozygous mutant mice, although mRNA expression levels are comparable to those in wild-type controls as confirmed by RT-PCR. (J:216506)