Genotype analysis, Northern blotting, and RT-PCR of TXAS^–/– mice. Genotyping was determined by Southern blot (A) and PCR (B) analyses. Tail DNA was isolated from WT (+/+), heterozygous (+/–), or homozygous (–/–) TXAS deletion littermates; digested with BstXI; and hybridized to probe B as described in Figure 1B. Bands corresponding to WT (7.0 kb) and mutant (7.9 kb) alleles are indicated. For Northern blotting (C) and RT-PCR (D), total RNA from spleen and thymus tissues was analyzed as described in “Materials and methods.” Lanes +/+, +/–, and –/– are WT, heterozygous, and TXAS^–/– littermates, respectively. The GAPDH fragment was used as an internal control and is shown at the bottom of panel C. Hybridization of the thymus RNA is shown with a 515-bp cDNA fragment of the exons 9 to 13 of TXAS. For RT-PCR, results of spleen and thymus samples are shown. M indicates 100-bp DNA ladders; and H₂O and Neg, experiments in which reaction conditions were the same as the others except that RNA (H₂O) or RT reaction (Neg) was omitted.