This study has shown that APCmin/+ mice and their wild-type litter mates (> 3 wk) can be genotyped using DNA isolated from whole fecal samples without the need for isolation of the colonic cells from the rest of the fecal mass. The collection technique is non-invasive to the mouse and therefore repeatable. Fecal pellet collection from mice aged greater than 3 wk was very simple, with the majority of mice providing a sample within 1 min. Collection of feces from mice younger than the weaning age (3 wk) was difficult due to their milk diet, and resulted in a poor DNA yield as the sample was small. DNA extraction from a mouse (> 3 wk) fecal pellet resulted in a yield of 20 - 350 ng/μL (average 75 ± 4 ng/μL (mean ± standard error)), and a purity (determined with the nanodrop OD260:OD280) of 2.02 ± 0.01. Following successful amplification of the DNA, running the PCR products on the gel allowed the determination of the genotype of the mouse.
To determine the accuracy of the genotyping with fecal samples, 28 wild-type and 28 APCmin/+ mice were genotyped with both fecal and small intestinal tissue DNA samples. There was 100% agreement between the results (Table ). Another validation of the genotyping results was completed by the presence or absence of small intestinal tumors in wild-type and APCmin/+ mice (n = 40/group). All mice established as APCmin/+ with the fecal DNA samples were found to have tumors in their small intestine at age 13 wk, compared to none of the wild-type mice (Table ). This validation shows 100% sensitivity and specificity of the genotyping.
Comparison of fecal genotyping result to other methods
The reproducibility of the genotyping with fecal samples was assessed by collecting and analyzing DNA from fecal pellets from mice on multiple occasions (with at least one week between collections). All samples gave the same genotype every time tested, showing the method to be reproducible (data not shown).