Abstract
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.

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