Genotypic and allelic frequency of a mutation in the NHEJ1 gene associated with collie eye anomaly in dogs in Italy

Background A 7.8-kb deletion in intron 4 of the NHEJ1 canine gene is associated with Collie Eye Anomaly (CEA). This deletion has been described in sheep-herding breeds related to the collie lineage and in several other dog breeds. A genetic test based on this association can distinguish three genotypes: normal, carrier and affected. The present study is a retrospective investigation of the presence of the CEA allele frequencies in selected breeds from the Italian dog population over a 10 year time span. Methods Genotype data, for the 7.8 kb deletion in intron 4 of the NHEJ1 gene, from 496 dogs belonging to Border collie (BC, n = 334), Shetland sheepdog (SS, n = 74), Australian shepherd (AS, n = 52), Nova Scotia duck tolling retriever (NS, n = 20) and rough collie (RC, n =16) were analysed. The genetic frequency of CEA allele was estimated in breeds with higher observations (BC, SS and AS). Results Healthy carriers were 50%, 45%, 29.6%, 17.3% and 12.5% in SS, NS, BC, AS and RC respectively. The affected recessive homozygotes were 81.3%, 10.8% and 1.5% in RC, SS and BC respectively. The CEA allelic frequencies were 0.36, 0.16 and 0.087 in SS, BC and AS, respectively. Conclusion The results support the usefulness of this type of genetic analysis to optimize care in dogs. The results support the usefulness of CEA mutated alleles analysis to optimize dogs’ care procedure in breeds where CEA mutation is present and to supply objective informations to be included in breeding programmes and in health risk evaluation in different canine breeds.