Genotyping mice

The text on this page is taken from an informal compilation of opinions of contributors to the online VOLE List. As such, they are not peer reviewed and may contain differences of opinion. Those wishing to contact the list may contact Adrian Smith.

DISTAL PHALANX AMPUTATION METHOD

We have one group that would need to genotype by p8 one harmful phenotypestrain (Homs exhibits tremors, ataxia, seizures and die by postnatal day 16). They are proposing distal phalanx amputation, so that they could genotype and identify at the same time the mouse. Animals (Heterozygotes) would need to go through some behavioural tests and rotarod after drug administration. I'm aware of the FELASA report on animal identification (Dahlborn et al 2013) and the paper by  Castelhano-Carlos et al. 2010. But I have few questions, related to what people are currently doing:

- If you have the distal phalanx amputation method in place, do you use anesthesia?

- Have you replaced this identification method with anything else?

- The paper by Castelhano-Carlos et al. reports the toe-clipping to elicit the smallest pain/distress related response in C57BL/6J pups at P5 and the technique doesn't impair the locomotor function activity test. Has anyone similar data on genetically modified phenotypes?

A challenging mouse strain by the sound of it. There's no need to mutilate the pups by amputating their toes though.

Eight-day old pups' ears are very small to sample but it might be worth checking exactly how much tissue is needed for the PI's PCR assay? A relatively larger ear biopsy might be justified in these circumstances. If a digit is taken, then much of the sample is bone, cartilage and connective tissue, so the gain in "analysable tissue" over skin may not be that great.

Or could you consider instead using a small oral swab, or even try swab from axillae (maybe you will get some dermal cells)?

Experimentally, the intention is to motor function test (rotorod) these mice, so perhaps having all their digits present would be an advantage, especially compared to their 18-toed controls?

I must confess to being a little sceptical of studies that find no locomotor difference in mice with missing digits, therefore justifying the method: It's quite likely that the mice are indeed able to walk around but the effect on other necessary natural functions, such as prehending food, grooming, climbing, etc may be overlooked in the follow-up assessment. (Besides the issue of pain from amputation and the animal's ability to show it during the neonatal phase).

Please leave digits alone, even at day 8. Ear biopsy for PCR is absolutely routine at day 10, and can also be used to identify the animals.