The loxP cassette in TI{TI}Srrm234^eMIC- has been excised, removing the Avic\GFP^3xP3.cUa marker. This leaves a Srrm234 locus with a 650bp deletion at the 3' end (removing the two possible terminal exons) and with an inserted sequence cassette in place of the deleted sequence. The inserted sequence cassette is flanked by inverted attP sites and includes 1. a splice acceptor site followed by 3 stop signals and a polyA signal (to ensure proper transcriptional termination) and 2. a single loxP site. The mutation is predicted to generate a C-terminal truncation of Srrm234 after the second-to-last exon, mainly affecting the coding region of isoforms that contain the enhancer of microexons (eMIC) domain, but also removing the last four amino acids of isoforms A and G. The presence of the inverted attP sites means that the entire inserted cassette can be replaced by recombination-mediated cassette exchange (RMCE) with a compatible donor plasmid (where the sequence to be inserted is flanked by inverted attB sites).