Thy1 promoter activity in the Rosa26 locus in mice: lessons from Dre-rox conditional expression system

Area of Science:

• Genetics and Genomics
• Molecular Biology
• Developmental Biology

Background:

• The Rosa26 locus is utilized for ubiquitous transgene expression in targeted transgenic (Tg) mice.
• The functional retention of tissue-specific promoters at the Rosa26 locus is not well understood.

Purpose of the Study:

• To evaluate the tissue-specific activity and reproducibility of exogenous promoters integrated into the Rosa26 locus.
• To assess the spatial expression patterns of transgenes driven by tissue-specific promoters at Rosa26.

Main Methods:

• Generation of Thy1-Dre/Dre reporter mice using pronuclear injection-based targeted transgenesis (PITT).
• Assessment of spatial transgene expression patterns in various organs.

Main Results:

• The Thy1 promoter targeted to the Rosa26 locus demonstrated activity in Purkinje cells of the cerebellum and hippocampus.
• Mosaic expression patterns were observed in other organs, consistent across all generated Tg lines.
• High reproducibility of expression patterns was noted for PITT-generated Tg lines.

Conclusions:

• Tissue-specific promoters can retain some functional properties when targeted to the Rosa26 locus.
• PITT enables reproducible generation of transgenic mice with predictable, albeit sometimes mosaic, expression patterns.
• Further investigation is needed to understand the mechanisms behind mosaicism in targeted transgenesis.