Genetically modified pigs have become a popular model system in fundamental research, agricultural and biomedical applications. However, random integration often result in unstable expression of transgene and unpredictable phenotypes. The Rosa26 locus has been widely used to produce genetic modified animals with high and consistent expressing of transgene in mouse, human and rat, as it can be targeted efficiently and is not subject to gene-silencing effects. Recently, the first case of reporter gene targeting pigs in porcine Rosa26 (pRosa26) locus was reported. In the study, full sequence of pRosa26 locus was further characterized, and the pRosa26 promoter (pR26) was cloned and we evidenced that the new porcine endogenous promoter is suitable for driving transgene expression in a high and stable manner by avoiding DNA methylation. Furthermore, elongation factor 1a promoter (EF1a) -driven GFP reporter and Myostatin promoter (MyoP)-driven Follistatin (Fst) were successfully targeted into the pRosa26 locusby traditional homologous recombination (HR) strategy. EF1a showed high activity and hypomethylation at the locus. And, muscle-specific promoter MyoP was activated strictly in muscle of the pRosa26 targeted pigs, indicating Rosa26 locus supports tissue-specific promoter driving transgene expression in its own manner. The study provided further demonstration on biomedical and agricultural applications of porcine Rosa26 promoter and locus.

Thanks for your answer, Bilal, could you please show me where you get this information ? the paper, for example. Actually, I need temporal-spatial expression pattern of Rosa26. Thanks !

ROSA stands for Reverse Orientation Splice Acceptor, named after the lentivirus gene trap vector. The ROSA26 allele is a defined locus on mouse chromosome 6 that has been used extensively for the targeted insertion of a wide variety of transgenes including fluorescent protein reporters under transcriptional control of ubiquitously expressed housekeeping genes. Control of cellular (de)differentiation in a temporal, cell-specific, and exchangeable manner is of paramount importance in the field of reprogramming. The ROSA26 mouse strain has one copy of the bacterial gene lacZ inserted into chromosome 6. The Rosa26 locus is one of most stable places to target single transgenes. In most cases, when Rosa26 is used, Transplantation studies and cell lineage analyses require the ability to explicitly distinguish morphologically identical cells that have an identifiable marker indicating their origin in vivo. Several reporter mouse strains have been generated for such studies, but pan-cellular detection of the marker in all tissues has not been achieved. In this report, we describe the generation of transgenic mice that express enhanced green fluorescent protein (EGFP) under control of a 187 kb bacterial artificial chromosome (BAC) containing the murine ROSA26 locus, and show several advantages over existing EGFP reporter lines. It is demonstrated that EGFP is ubiquitously and reproducibly expressed from the murine BAC transgene in all organs and tissues analyzed, including the hematolymphoid compartment. Attached Figure . Strategy for the rapid generation of conditionally overexpressing ES cells. Schematic representation of the wild-type Rosa26 (R26) locus, the pre-targeted R26 Hygro and the recombined R26 alleles.