Gt(ROSA)26Sor^{tm1(CAG-mCherry/Rpl10a)Sten}

The "floxed translating ribosome affinity purification (TRAP)" insertion encodes an mCherry-tagged ribosomal protein L10A, which incorporates into and fluorescently labels polysomes in cell lineages determined by the cell type-specific expression of cre recombinase. As mRNAs encoding expressed proteins are attached to polysomes during their translation, the transcripts active in a cell or lineage at times from the onset of cre expression can thus be identified. The introduced segment contains an mRNA splice acceptor sequence followed by a puromycin resistance cassette and polyadenylation signal; the CAG promoter, comprising the cytomegalovirus (CMV) immediate ealy (IE) enhancer and chicken beta-actin promoter, blocked by a loxP-flanked triple SV40 polyadenylation signal (tpA); and the mCherry coding sequence joined to the 5' end of that for ribosomal protein L10A (encoded by the Rlp10a gene), followed by the rabbit beta-globin polyadenylation signal. Cre recombinase excision of the floxed tpA permits expression of the fusion protein under control of the ubiquitous CAG enhancer/promoter. The selection of the cre recombinase transgene or knockin allele thus provides spatiotemporal control of the expression of the fluorescently tagged L10A protein. (J:210222)