CycB1-GFP transgenic mice express enhanced green fluorescent protein (EGFP) fused to the 105 N-terminal residues of the Cyclin B1 (Ccnb1) gene. This portion of Cyclin B1 (known as the "destruction box") is ubiquitinated by APC/C complex, directing the protein for degradation when APC/C is active. Due to the cell cycle stage specific nature of APC/C activity, only cells that are in S-G2-M stages of the cell cycle express the CycB1-GFP protein. Expression is driven by the housekeeping, constitutive mouse phosphoglycerate kinase 1 (Pgk1) promoter and the reporter is detected in a range of tissues in vivo. The transgene was introduced using a viral vector.
Of note, the transgene was introduced using a viral vector and is integrated in
multiple loci. These mice are kept mostly inbred but with time, variation in the level of expression is evident. This becomes more frequent when mice are outbred. As such, genotyping the mice by PCR does not always reflect the transgene expression level. Monitoring GFP level in ear fibroblasts prepared from individual mice is the preferred method for genotyping. Mice with good expression are chosen for analysis and for further breeding.
