Cover Picture: Eur. J. Immunol. 9/10

This issue's cover consists of a collage of images taken from Monnich et al. (pp. 2379–2384). In this elegant study, the authors describe the identification and characterization of two deleterious mutations in the zebrafish topoisomerase III alpha (top3a) gene that reveal an unexpected tissue-specific requirement of top3a function in developing thymocytes. In the forefront, the structure of the E. coli Top3 protein in complex with ssDNA substrate is depicted. In the background, the image depicts a lateral view of rag1-specific RNA in situ hybridization in a 5-day post-fertilization zebrafish embryo, allowing for the detection of differentiating thymocytes.