Cardiac puncture is a suitable technique to obtain a single, large, good quality sample from a euthanised mouse or a mouse under deep terminal anaesthesia if coagulation parameters, a separate arterial or venous sample or cardiac histology are not required. It is appropriate for all strains of mouse.

The purpose of a tail snip is to obtain a small amount of tissue and/or blood from a rodent to prepare DNA for genotyping or other analysis. The technique involves the removal of the fleshy tail tip, thus avoiding the bony vertebral segments. A tail snip is easily performed on mice ≤21 days.

Genotyping is the process of detecting the presence, or absence, of specific DNA sequences in a particular organism’s genome. Since genes can influence a mouse’s phenotype, being able to probe an individual mouse’s genetic make-up, or “genotype,” is critical for attributing a phenotype to a specific gene.

Tail snipping procedure:

1. Gently, but securely, restrain animal (manual or mechanical)
2. Snip tail with sanitized sharp scissors or disposable blade.
3. Place tail tip into a tissue collection tube.
4. Ensure hemostatis (stop bleeding):
5. Return animal to its cage and monitor for bleeding for at least 5 minutes.

The tail of a mouse or rat may be repulsive to some, but to the small rodent, it provides balance, and acts as an effective temperature regulator.

Humane endpoints refer to one or more predetermined physiological or behavioral signs that define the point at which an experimental animal’s pain and/or distress is terminated, minimized or reduced by taking actions such as euthanizing the animal, terminating a painful procedure or giving treatment to relieve pain and …

There are several ways to obtain DNA for mouse genotyping. You can collect DNA from ear tissue (0.5 to 2 mm) using an ear punch. This yields a larger quantity of quality DNA. Ear tissue is easy to collect when mice are ear punched for identification.

Genotype is the genetic make-up of an individual organism. Your genotype functions as a set of instructions for the growth and development of your body.

Protocol

1. Cut toe and place in a thin-walled PCR tube, and freeze until ready to elute DNA.
2. Add 75µL of base solution 1X working stock to each sample.
3. Place tubes at 95° in a PCR machine (or bath or block) for 30 minutes.
4. Cool to room temperature or below.
5. Add 75µL neutralization solution 1X working stock and vortex.

between 10-21 days old
The optimal age for genotyping is between 10-21 days old. Tail biopsies at this age give the highest yield of DNA per mm. In general, tail vertebrae in pre-weaning age mice are not fully ossified and removing the tail tip produces minimal pain and distress (5).

Tail Structure A mouse’s tail is usually a similar color to the rest of its skin, so it may be pink, dark gray or even tan. Mice tails are not prehensile and stay low to the ground regardless of the mouse’s posture.

Other fun facts about the skeleton of mice They have five cranial ridges that unite different bones. Their tail is made up of approximately 20 vertebras, which are called coccygeal vertebrae. Young female mice have ligaments that connect the pubic bones. After giving birth, these bones diverge.

Gently, but securely, restrain animal (manual or mechanical) Snip tail with sanitized sharp scissors or disposable blade. DO NOT remove more than 5mm of tail. Place tail tip into a tissue collection tube. Check for bleeding, if bleeding occurs: Apply pressure to the cut portion of the tail with gauze until bleeding has stopped.

IACUC Policy: Rodent Tail Snipping for Genotyping. If continuous pressure does not stop the bleeding, utilize a chemical cautery agent (e.g. silver nitrate or Kwik Stop®) Return animal to its cage Clean off biologic material (e.g. blood or fur) from scissors and sanitize after each snipping.

FELASA Guidelines for the Refinement of Methods for Genotyping Genetically-modified Rodents: A Report of the Federation of European Laboratory Animal Science Associations Working Group 47.3 (2013): 134-45. Hankenson, F CLaire, Laura M. Garzel, David D. Fischer, Bonnie Nolan, and Kurt D. Hankenson.