OCHSNER CLINIC FOUNDATION
Animal Care and Use Committee
Identification and Genotyping Methods in Mice
I.
Objective
To define biopsy methods in mice that will provide a source of genomic DNA for molecular
genotyping as well as identification options.
II. Responsibility
The investigator is responsible for ensuring that biopsy and identification methods in mice
are done under aseptic conditions and the use of analgesia or anesthesia is commensurate
with the age of the rodent.
III. Procedures
A. Biopsy/genotyping
1. Sampling must be performed using sharp, clean instruments.
2. Bleeding after sampling should be treated by either use of chemical cauterizing
agents (styptic powder and silver nitrate are recommended), compression of the
sample site by direct pressure, or if necessary by electrocautery.
3. If anesthesia is use, animals must be observed until recovery from anesthesia.
4. Instruments must be disinfected between animals and sharpened regularly to
ensure minimization of tissue injury.
B.
Genotyping and identification methods.
1. Toe-clipping.
a) Toe clipping should be used only when no other individual identification
methods is feasible.
b) Toe clipping of neonatal can be applied to mice up to 7 days without
anesthesia.
c) If clipping of toes is to occur after day 8, it must be justified in the protocol
and done using local anesthesia (i.e. immersion of foot in cold ethanol,
application of ethyl chloride spray, lidocaine treatment, etc).
d) If toe clipping is used, it should also serve as a tissue sample. Note that it is
unnecessary to remove the entire toe. Removal of the distal half of each toe
in question is sufficient to permit identification.
2.
Ear-punching
a)
The procedure should be performed on weaned mice as a method of
identification as well as to obtain tissue for genotyping.
b) Ear punching of weaning mice does not require anesthesia. However,
application of multiple punches requires skill as torn punches can make
identification difficult or impossible.
C.
Genotyping methods only.
1. Tail snipping.
a) This method refers to the amputation of the distal 5mm or less of tail tissue in
order to obtain DNA for genotyping.
b) The tail snip is not useful for identification of mice.
c) Tail biopsies should preferably be taken from animals between the ages of 8
and 12 days of age because there is a lack of nervous system development,
bleeding is minimal, and anesthesia is not required.
d) After day 12, anesthesia is required because of the developed vascular and
nervous system.
e) Investigators are encouraged to apply local anesthesia to the tail (i.e.
immersion of tail in cold ethanol, application of ethyl chloride spray, lidocaine
treatment, etc.).
f) IACUC approval is necessary if greater than 5mm of tail is snipped.
g) If removing more than 5mm of the tail tip on mice 21 days of age or old,
general anesthesia and analgesia is required and only trained members
should perform the procedure to ensure bone is not cut.
h) There must be scientific justification for conducting tail snips on animals after
21 days and for not using analgesics.
i) Repeated tail clips on a single mouse require the prior approval of the IACUC.
2.
Ear Snipping.
a) This practice of tissue collection requires the removal of 2-3mm of tissue
from the ear pinna with preferably sharp scissors to obtain tissue.
b) Ear biopsies should preferably be taken from animals between the ages of 8
and 12 days of age because there is a lack of nervous system development,
bleeding is minimal, and anesthesia is not required.
c) After day 12, local anesthesia is required because of the developed vascular
and nervous system.
d) Repeat ear snips from the same ear would require IACUC prior approval.
3.
Buccal swabs/saliva.
a) The method is non-invasive that can be performed without anesthesia on any
age of mouse. Cotton swabs are used to retrieve cheek cells from the mouths
to be used for the genotyping.
4.
Blood Samples
a) Can be obtained using any standard blood collection method.
b) IACUC protocol must specifically state blood collection method and amount
to be collected.
c) The veterinary staff will decide if anesthesia is necessary for the blood
method.
5.
Hair bulbs
a) The method involves plucking a small amount of hair from the animal to use
for genetic analysis. The method is non-invasive and does not require
anesthesia at any age.
6.
Fecal pellet
a) Stool can be collected for use in genetic sampling. Collecting stool is noninvasive and can be collected directly from the animal or the cage.
D. Identification methods only
1. Ear tagging identification: The method includes attaching a metal tag to the ear of
the rodent that corresponds to a unique identification number.
2. Anesthesia is not required for the procedure, but rodents must be at weaning age
or older.
3. The ear tag must be disinfected or sterilized before being attached to the animal.
E.
Tattooing
1. A permanent mark is made on the tail, toes, or possibly foot pads by using a
needle or appropriate micro-tattooing device.
2. Anesthesia is not required for this method.
F.
Permanent Marker (Sharpie®)
1. This method is for a temporary identification procedure, a permanent marker can
be used to uniquely color the tail for purpose of short term identification.
2. This method is non-invasive and does not require anesthesia.