Targeted Disruption of the taut Gene

An 18-kb XhoI genomic clone was isolated from a l phage library containing mouse strain 129SvJ genomic DNA by screening with a cDNA taut probe (Heller-Stilb et al., 2002). To disrupt the taut locus, an isogenic targeting vector was designed to delete exon 1 of taut. Embryonal stem cells

(ES) cells (derived from 129/SvJ strain) were electroporated with the linearized vector, and colonies underwent positive—negative selection with genet-icin and gancyclovir (Mansour et al., 1988). Double-resistant clones were screened for the desired homologous recombination by polymerase chain reaction (PCR). After analysis of PCR-positive clones by Southern blot hybridization, ES clones containing the targeting event were injected into blastocysts ofC57BL/6 mice to produce chimeras. Heterozygous (taut+/—) mice from ES clones, which transmitted the taut mutation through the germ line, were intercrossed to produce wild-type (taut+/+), heterozygous (taut+/—), and homozygous (taut—/—) animals in the F2 progeny.

2. Reduced Taurine LeveLs Lead to Various Diseases in taut-/- Mice

The deletion of exon 1 of the taut gene leads to a truncated, nonfunctional protein of 450 amino acids (wild-type: 621) as shown by in vitro transcription and translation assays and measurement of taurine uptake in fibroblasts from the null mutation (Heller-Stilb et al., 2002).

taut-/- mice exhibit an up to 25% lower body mass compared with taut+/- and wild-type mice (Fig. 25.1). Taurine tissue levels are strongly reduced in taut-/- mice when compared with wild-type mice (HellerStilb et al., 2002; Warskulat et al., 2004, 2006b): taut-/- mice exhibit a

Figure 25.1 taut—/— mice exhibit a lower body mass compared with taut+/— and wildtype mice. Body masses of male taut—/—, taut+/— and wild-type mice are shown. Data are expressed as means ± SEM (n = 5-17; *P < 0.05 vs wild-type mice).

Figure 25.1 taut—/— mice exhibit a lower body mass compared with taut+/— and wildtype mice. Body masses of male taut—/—, taut+/— and wild-type mice are shown. Data are expressed as means ± SEM (n = 5-17; *P < 0.05 vs wild-type mice).

decrease in taurine levels in skeletal and heart muscle by about 98% and in brain, retina, kidney, liver, and plasma by 70 to 90%. In addition to a reduced fertility (Heller-Stilb et al., 2002), taut—/— mice show various pathologies, for example, reduced exercise capacity (Warskulat et al., 2004), changes in neuroreceptor expression (Oermann et al., 2005), and loss of long-term potentiation in the striatum (Sergeeva et al., 2003), and develop loss of vision (Heller-Stilb et al., 2002; Rascher et al., 2004) and hearing (Jiang et al., 2005), olfactory dysfunction (Witt et al., 2003), altered renal osmoregulation (Huang et al., 2006), and liver disease (Warskulat et al., 2006b). Interestingly, circulating erythrocytes from taut—/— mice are slightly but significantly more resistant against suicidal cell death following osmotic shock (Lang et al., 2003).

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