Project Objectives
- Test and optimise an RU486 micropipette‑guided drug administration method.
- Compare tamoxifen and RU486 toxicity in mice.
- Evaluate recombination efficiency and specificity of Cre‑Rux/RU486 compared to Cre‑ERT2/tamoxifen.
- Determine the RU486 dose with the best balance of low side effects and sufficient recombination.
- Validate RU486 effects in longer‑term, multi‑sex studies.
- Provide proof‑of‑principle for adopting Cre‑Rux/RU486 as a refined alternative to Cre‑ERT2/tamoxifen.
3Rs Impact
- Enables refinement by reducing toxicity, stress, and non‑specific effects associated with tamoxifen.
- Reduces animal numbers required by improving system specificity and reproducibility.
- Potential to replace stressful oral gavage procedures with voluntary RU486 administration.
- Has widespread relevance given the extensive use of Cre‑ERT2 systems.
Background
Biomedical research relies on the genetic manipulation of animals such as mice, as experimental models to mimic human diseases and to determine their mechanisms. A well-used system for gene editing relies on the enzyme Cre recombinase, however a variant of this enzyme, CreERT2, requires the drug tamoxifen to be active. It has become apparent that tamoxifen administration can be problematic though. Reports show that tamoxifen can be toxic to mice, tamoxifen is unspecific, and moreover, some experimental setups require forced oral administration of tamoxifen, which is a stressful procedure.
In light of this, the research team will evaluate Cre‑Rux (which is activated using the drug RU486 rather than tamoxifen) as an alternative to Cre. The two systems, Cre and Cre-Rux, will be compared, as will the potential for RU486 to be delivered using voluntary micropipette‑guided drug administration, to avoid the stress associated with forced oral administration. The aim is to create a refined, more humane and reliable approach for genetic manipulation in mice.
