Impact of Allogrooming in Domestic Cats (Felis silvestris catus) on Mitochondrial DNA Profiling of Shed Hairs

Allogrooming is a normal behavior for socially bonded cats. Cat hairs may have epithelial cells on the shaft from at least two cat contributors, the host (groomee) and the donor (groomer). To determine the likelihood of obtaining a mixture or incorrect DNA profile in cat hairs, feline mtDNA control region from hairs of allogrooming cats was isolated and analyzed by direct sequencing. Two DNA extraction methods were tested; hair washes and complete digestion of hairs. For five allogrooming pairs with different mitotypes, thirteen of the 126 sequences (10.3%) matched the mitotype of the groomer, not the groomee. Forty-three sequences (34.13%) suggested the presence of both mitotypes, groomer and groomee. Approximately 2.4% of mtDNA sequences appeared heteroplasmic at mitotype defining sites. Heteroplasmy was not observed in 157 control sequences. Mitotypes from the groomer was 11-fold more difficult to obtain from hairs that were completely digested before DNA isolation and was not observed in samples if the hairs were washed prior to digestion. Unlike contamination issues in human forensic cases, obtaining more than one mtDNA profile from a feline hair sample could narrow the pool of suspects since the implicated cat(s) would have to be within the same vicinity and have social contact.