Deletion within the second exon of Nopp140. A loxP cassette containing the Disc\RFPDsRed(T1).3xP3.cHa marker and a single attP site have been inserted in place of the deleted Nopp140 sequence as part of the mutagenesis event; the direction of transcription of the marker is expected to be opposite to that of Nopp140 (due to the orientation of the homology arms used in the donor plasmid).