Policies> Rodent Tail Biopsy
For the production of genetically altered rodents, it is often necessary to sample tissue for DNA analysis. Usually, the end of the tail is sampled. The following policy will ensure the humane sampling of tissue for biopsy from rodents. Investigators are encouraged to maintain animals in a homozygous state whenever possible to minimize or eliminate the need for tail biopsy. Furthermore, using PCR vs. Southern blot for genotyping, when possible, reduces the tissue requirement and permits using ear punches and saliva for genotyping.
In the mouse, the terminal tail ossifies between 2 and 4 weeks of age. Thus, tail sampling is recommended in mice less than three weeks of age.
In mice of this age (<21d), the distal tail biopsy may be performed without anesthesia, if less than 5 mm of tail snip is to be removed. 2mm or less is recommended for PCR.
Animals over 3 weeks of age (>21d) must be anesthetized with a short acting anesthetic
Local anesthesia – may be achieved by immersion of the tail in ice-cold ethanol for ten seconds. Alternatively, the tail may be disinfected followed by an application of ethyl chloride spray or other suitable anesthetic as recommended by the Attending Veterinarian.
General anesthesia – (e.g., inhaled isoflurane)
Mice should be identified using an appropriate method (e.g. ear punch, ear tag, transponder, etc.) at the time of tail biopsy.
Sampling must be performed using sharp, sterile/sanitized cutting devise, e.g. scalpel blade, utility razor blade, surgical scissors. If tail biopsies are performed on multiple mice, instruments must be disinfected appropriately between animals. It is recommended that the use of each blade be limited to no more than 5 times.
The smallest possible section of tail should be removed; it is recommended that TOTAL tail sampling be limited to no more than 5mm of tissue.
Adequate hemostasis must be achieved via a styptic (e.g., silver nitrate, cautery, tissue adhesive, etc.).
Alternatives to tail biopsies should be considered:
Tissue can be obtained by ear punching which can also serve as identification,
Small quantities of blood from distal veins (e.g., saphenous vein) may be used for analysis, PCR analyses using saliva and hair have also been described among others. Gentra Systems and Sigma each have DNA kits for whole blood; Gentra Systems has a salivary DNA kit
References:
1. Irwin, M.H.; Mofatt, R.J.; Pinkert, C.A. Identification of Transgenic Mice by PCR Analysis of Saliva. Nature Biotechnology (1996) 14, 1146-1148.
2. Schmitteckert, E.M.; Prokop, C.; Hedrich, H.J. DNA Detection in Hair of Transgenic Mice—A Simple Technique Minimizing the Distress on the Animals. Laboratory Animals (1999) 33(4), 385-389.
3. Zimmermann, K; Schwarz, H.P.; Turecek, P.L. Deoxyribonucleic Acid Preparation in Polymerase Chain Reaction Genotyping of Transgenic Mice. Comparative Medicine (2000) 50(3), 314-316.
4. Pinkert, CA. Transgenic Animal Technology: Alternative in Genotyping and Phenotyping. Comparative Medicine (2003) 53(2): 126-139.
