Yale University Policy and Procedures for Mouse Tail Clipping for DNA Analysis

Yale University
Institutional Animal Care
& Use Committee
New Haven CT
USA 06510

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Yale University Policy and Procedures for Mouse Tail Clipping for DNA Analysis

Background:

Genotyping of transgenic animals in a litter is critical to the efficient pursuit of research and in reducing the number of animals involved in a research project. Most often the genotype is determined by analysis of DNA extracted from tissues of young mice. Analysis by the Polymerase Chain Reaction (PCR) requires the least amount of DNA. DNA for PCR analysis can be obtained from ear punches, hair samples, or oral swabs. Depending on the requirements of the study, investigators are required to consider these alternatives. Larger amounts of DNA are required for Southern Blot determination of the genotype. Obtaining tissue from a mouse for DNA analysis via tail biopsy is a safe, effective and humane procedure that causes minimal or transient pain and distress when performed properly. DNA prepared from tail biopsies is suitable for analysis by either Southern Blot or PCR.

Policy:

No more than 5 mm of tail should be removed from any one animal. If proper procedures are followed, the DNA yield from 5 mm of tail should exceed 50 micrograms, enough for multiple analyses. The DNA yield does not increase proportionally with tail fragment size. If small amounts of DNA are required, investigators should consider taking only 2 mm of tail.
Animals should be 10-21 days of age when performing tail clipping.
Alternatives to tail clipping must be considered for animals older than 21 days of age*. Scientific justification must be provided in the protocol if alternative methods cannot be used.
- Ear punch
- Hair sampling
- Oral swabs
*Performing tail clips on animals over 21 days of age is considered a painful procedure due to the likelihood of bone involvement. Hemostasis is also a problem. If tail clips are necessary, along with the scientific justification, animals are to be placed in USDA Pain Category D, a description of anesthesia, post-procedural analgesics, and monitoring must be provided.

Guidelines for Tail Clipping:

Materials Needed:

Straight Iris Scissors or disposable razor blades
Cautery Pen or Silver Nitrate Sticks
Small Forceps
Eppendorf or other tubes to hold samples
Fine tip permanent marker to label tubes
Ear punch or ear tags and applicator
Ice Bucket, Ice
Paper Towels
Non-sterile Gloves
Disinfectant solution (Clidox, Nolvasan, Alcohol, etc)
Clean cage for transfer of animals

Prior to beginning:

Determine numbering system to be used in identification of animals and any specific records to be kept

Procedure:

Lay out materials and place paper towels on a work surface
- If animals are older than 21 days, include anesthesia and post-procedural analgesics
Bring one cage at a time to the work area to avoid confusion
Count number of animals in the cage and write their designated ID numbers on cage card. As you work it may also be helpful to indicate coat color of each mouse along with its number for future reference.
Label vials with corresponding cage animal numbers
Restrain the first mouse by scruff of neck and ear punch or tag with appropriate number
Verify that animal ID, vial and cage card number are the same. This is extremely important.
Place the mouse on cage top so that it grips it as you hold the animal by its tail, approximately 2 cm from the end.
Excise a maximum of 5 mm piece from the end of tail with iris scissors or razor blades, allowing it to fall onto paper toweling.
Cauterize the end of tail to stop bleeding; once stopped place the mouse into a transfer cage
Pick up the tail sample with forceps and place into the corresponding-numbered vial
Place the vial on ice for holding.
Continue with each mouse in the cage.
Return mice to the original cage, check again for any bleeding and return to same position on the rack.
To avoid wound and DNA cross-contamination disinfect scissors or razorblades between animals with a disinfectant that is compatible with the assay you need to run.
Continue until all animals requiring testing have been sampled.

Clean Up:

Thoroughly wash instruments and either disinfect chemically with Clidox solution, rinsing again afterwards to remove chemical contaminants OR sterilize by steam or ethylene oxide gas.

REVIEWED AND APPROVED BY THE IACUC: July 21, 2004