Wolfgang Hans

Type I Bartter syndrome is a recessive human nephropathy caused by loss-of-function mutations in the SLC12A1 gene coding for the Na⁺-K⁺-2Cl⁻ cotransporter NKCC2. We recently established the mutant mouse line Slc12a1 ^I299F exhibiting kidney defects highly similar to the late-onset manifestation of this hereditary human disease. Besides the kidney defects, low blood pressure and osteopenia were revealed in the homozygous mutant mice which were also described in humans. Beside its strong expression in the kidney, NKCC2 has been also shown to be expressed in other tissues in rodents i.e. the gastrointestinal tract, pancreatic beta cells, and specific compartments of the ear, nasal tissue and eye. To examine if, besides kidney defects, further organ systems and/or metabolic pathways are affected by the Slc12a1 ^I299F mutation as primary or secondary effects, we describe a standardized, systemic phenotypic analysis of the mutant mouse line Slc12a1 ^I299F in the German Mouse Clinic. Slc12a1 ^I299F homozygous mutant mice and Slc12a1 ^I299F heterozygous mutant littermates as controls were tested at the age of 4–6 months. Beside the already published changes in blood pressure and bone metabolism, a significantly lower body weight and fat content were found as new phenotypes for Slc12a1 ^I299F homozygous mutant mice. Small additional effects included a mild erythropenic anemia in homozygous mutant males as well as a slight hyperalgesia in homozygous mutant females. For other functions, such as immunology, lung function and neurology, no distinct alterations were observed. In this systemic analysis no clear primary effects of the Slc12a1 ^I299F mutation appeared for the organs other than the kidneys where Slc12a1 expression has been described. On the other hand, long-term effects additional and/or secondary to the kidney lesions might also appear in humans harboring SLC12A1 mutations.

Background: The mouse inbred line C57BL/6J is widely used in mouse genetics and its genome has been incorporated into many genetic reference populations. More recently large initiatives such as the International Knockout Mouse Consortium (IKMC) are using the C57BL/6N mouse strain to generate null alleles for all mouse genes. Hence both strains are now widely used in mouse genetics studies. Here we perform a comprehensive genomic and phenotypic analysis of the two strains to identify differences that may influence their underlying genetic mechanisms. Results: We undertake genome sequence comparisons of C57BL/6J and C57BL/6N to identify SNPs, indels and structural variants, with a focus on identifying all coding variants. We annotate 34 SNPs and 2 indels that distinguish C57BL/6J and C57BL/6N coding sequences, as well as 15 structural variants that overlap a gene. In parallel we assess the comparative phenotypes of the two inbred lines utilizing the EMPReSSslim phenotyping pipeline, a broad based assessment encompassing diverse biological systems. We perform additional secondary phenotyping assessments to explore other phenotype domains and to elaborate phenotype differences identified in the primary assessment. We uncover significant phenotypic differences between the two lines, replicated across multiple centers, in a number of physiological, biochemical and behavioral systems. Conclusions: Comparison of C57BL/6J and C57BL/6N demonstrates a range of phenotypic differences that have the potential to impact upon penetrance and expressivity of mutational effects in these strains. Moreover, the sequence variants we identify provide a set of candidate genes for the phenotypic differences observed between the two strains.

Background: InDrosophila, mutations in the geneeyes absent(eya) lead to severe defects in eye development. The functions of its mammalian orthologsEya1-4are only partially understood and no mouse model exists forEya3. Therefore, we characterized the phenotype of a newEya3knockout mouse mutant.Results: Expression analysis ofEya3byin-situhybridizations and β-Gal-staining ofEya3mutant mice revealed abundant expression of the gene throughout development, e.g. in brain, eyes, heart, somites and limbs suggesting pleiotropic effects of the mutated gene. A similar complex expression pattern was observed also in zebrafish embryos.The phenotype of young adultEya3mouse mutants was systematically analyzed within the German Mouse Clinic. There was no obvious defect in the eyes, ears and kidneys ofEya3mutant mice. Homozygous mutants displayed decreased bone mineral content and shorter body length. In the lung, the tidal volume at rest was decreased, and electrocardiography showed increased JT- and PQ intervals as well as decreased QRS amplitude. Behavioral analysis of the mutants demonstrated a mild increase in exploratory behavior, but decreased locomotor activity and reduced muscle strength. Analysis of differential gene expression revealed 110 regulated genes in heart and brain. Using real-time PCR, we confirmedNup155being down regulated in both organs.Conclusion: The loss ofEya3in the mouse has no apparent effect on eye development. The wide-spread expression ofEya3in mouse and zebrafish embryos is in contrast to the restricted expression pattern inXenopusembryos. The loss ofEya3in mice leads to a broad spectrum of minor physiological changes. Among them, the mutant mice move less than the wild-type mice and, together with the effects on respiratory, muscle and heart function, the mutation might lead to more severe effects when the mice become older. Therefore, future investigations ofEya3function should focus on aging mice.