Real-time PCR quantification of the canine filaggrin orthologue in the skin of atopic and non-atopic dogs: a pilot study

BACKGROUND: Canine atopic dermatitis (AD) is a common inflammatory skin disease associated with defects in the epidermal barrier, particularly in West Highland white terriers (WHWTs). It shares many similarities with human AD, and so may be a useful animal model for this disease. Epidermal dysfunction in human AD can be caused by mutations in the gene encoding the epidermal protein filaggrin (FLG) and, in some atopic patients, be associated with altered FLG mRNA and protein expression in lesional and/or non-lesional skin. In experimental models of canine AD, mRNA expression of the orthologous canine filaggrin gene may be reduced in non-lesional skin compared with healthy controls. However, there is no published data on canine filaggrin mRNA expression in the skin of dogs with naturally-occurring AD. Hence, the aim of this pilot study was to develop a reverse transcriptase real-time PCR assay to compare filaggrin mRNA expression in the skin of atopic (n = 7) and non-atopic dogs (n = 5) from five breeds, including eight WHWTs. FINDINGS: Overall, filaggrin mRNA expression in non-lesional atopic skin was decreased compared to non-lesional non-atopic skin (two fold change); however this difference was only statistically significant in the subgroup of WHWTs (P = 0.03). CONCLUSIONS: Although limited by the small sample size, these results indicate that, comparable to some cases of human AD, altered filaggrin mRNA expression may exist in the skin of some atopic dogs with naturally-occurring disease. Additional studies, including larger sample numbers, will be necessary to confirm this finding and to investigate whether mutations in the filaggrin gene exist and contribute to epidermal lesions of AD in dogs.