(A) Schematic representation of the Fus gene locus (upper panel). Lower panels depict exons 11-15 in the wild type allele (left) and ∆NLS allele (right) with localization of PCR primers used for genotyping (gDNA, used in B) and for RT-PCR (Total and ∆NLS, used in C). Arrow: translational start site. STOP cassettes are indicated in red; loxP sites as black triangles; coding regions are in dark blue and UTRs in light blue. Location of the region encoding the nuclear localization signal (NLS) is indicated in exon 15. 