Animal Care and Use Policies and Guidelines

Tail Biopsy Guidelines for Mice(1)

In order to determine if transgenic mice carry a gene of interest, tail biopsies or “snips” are commonly performed to obtain DNA samples.  Obtaining tissue from a mouse for DNA analysis via tail biopsy is a safe, effective and humane procedure when performed properly.  DNA prepared from tail biopsies is suitable for analysis by either Southern Blot or PCR.  DNA can also be obtained from ear punches, hair samples, or oral swabs (see references 1-6).

1. Procedures for performing tail biopsies for genotyping and/or DNA analysis must be described in the protocol.
2. Anesthetize the mouse, if required.  Restrain, or grasp, the mouse between thumb and forefinger.  This is a convenient time to identify the animals using the appropriate method (i.e. ear punch, ear tag, toe tattoo, transponder etc.).  Clean the tip of the tail with 70% ethanol.
3. With a sterile razor blade, scalpel, or sharp scissors, cleanly excise up to 5mm of the tail. Less tail may be taken, however more than 5mm requires justification in the protocol. If you prefer, the tail may be placed on a disinfected work surface for performing this procedure.  When executed properly, a 5mm segment of tail should yield over 50 micrograms of DNA, enough for multiple analyses.  Note: the yield of DNA does not proportionally increase with the use of tail fragments larger than 5mm.  When performing snips on more than one animal at a time, care should be taken to remove all tissue from the instruments between animals. 
4. Following the procedure, bleeding should be controlled using local pressure, applying styptic powder or silver nitrate to the tail tip, or cauterization by heating the razor blade or scalpel in the flame of a small alcohol burner before cutting.  Keep in mind that heating dulls the blade and may not be appropriate when cutting with non-disposable scissors.  Note: cauterizing agents are toxic to mice if ingested; use with caution.  After ensuring that the bleeding is stopped, the mice must be monitored after release back into their cages to ensure bleeding does not re-start.

For mice less than 22 days of age: When tail biopsies are performed on young mice the yield of DNA is highest and therefore could require a smaller portion of the tail to be taken.  Also, prior to three weeks of age the tail vertebrae are not fully ossified8. Consequently, these mice can be placed in USDA Pain Category C.  In addition, prompt analysis of tail tissue allows the desired mice to be identified prior to weaning, which can facilitate more efficient use of cage space and optimize colony management to reduce the number of animals produced.

For mice 22 days or older: the use of a general anesthetic is required prior to collection of tissue from the tail, and described in the protocol.  Isoflurane is the recommended anesthetic.  Consult with the attending veterinarian for other options.  In this situation, when mice that undergo tail biopsy are older than 22 days, they must be placed in USDA Pain Category D. However, protocol question 17b does not need to be filled out.

[1] Approved by the JHU Animal Care and Use Committee on: April 16, 2009

References:

1.  Hofstetter JR, Zhang A, Mayeda AR, Guscar, T, Numberger JI and Lahiri DK.  Genomic DNA from Mice: A comparison of Recovery Methods and Tissue Sources.  Biochem Mol Med, 1997, Dec; 62(2): 197-202.

2.  Dennis, MB.  IACUC Review of Genetic Engineering.  Lab Animal 2000, Mar; 29(3): 34-37.

3.  Irwin MH, Moffatt RJ and Pinkert CA.  Identification of Transgenic Mice by PCR Analysis of Saliva.  Nat Biotechnol. 1996, Sep; 14(9): 1146-8.

4.  Schmitteckert EM, Prokop CM and Hedrich HJ.  DNA Detection in Hair of Transgenic Mice – A Simple Technique Minimizing the Distress on the Animals. Lab Animal 1999; 33-4:385-389.

5.  Couse JF, Davis VL, Tally WC and Korach KS.  An Improved Method of Genomic DNA Extraction for screening Transgenic Mice.  National Institute of Environmental Health Sciences, National Institutes of Health.  BioTechniques.  1994, 17:1030-1032.

6.  Malumbres M, Mangues R, Ferrer N, Lu S and Pellicer A. Isolation of High Molecular Weight DNA for Reliable Genotyping of Transgenic Mice.  BioTechniques.  1997, 22/6:1114-1119.

7.  Fitzgerald, M and Gibson, S.  The postnatal physiological and neurochemical development of peripheral sensory C. fibres.  Neuroscience.  1984, 13(3): 933-944.

8.  Hankenson FC, Garzel LM, Fischer DD, Nolan B, Hankenson KD. Evaluation of Tail Biopsy Collection in Laboratory Mice (Mus musculus): Vertebral Ossification, DNA Quantity, and Acute Behavioral Responses. Journal of the American Association for Laboratory Animal Science, 2008, 47:6 10-18