Uppsala, Sweden –

A new study conducted by researchers from four international universities concluded that an inherited neurological disorder affecting Golden Retrievers is caused by a DNA mutation that occurs through maternal inheritance.

Researchers from the Swedish University of Agricultural Sciences, Norwegian School of Veterinary Science,  Uppsala University and the Karolinska Institute did pedigree analysis to reveal that all affected dogs belong to one maternal lineage, and a statistical analysis showed that the disorder has a mitochondrial origin.  A one base pair deletion in the mitochondrial tRNA^Tyr gene was identified at position 5304 in affected dogs after re-sequencing the complete mitochondrial genome of seven individuals. The deletion was not found among dogs representing 18 different breeds or in six wolves, ruling out this as a common polymorphism. The mutation could be traced back to a common ancestor of all affected dogs that lived in the 1970s. These results provide conclusive evidence that the deletion in the mitochondrialtRNA^Tyr gene is the causative mutation for SAN.

Sensory ataxic neuropathy (SAN) is a recently identified neurological disorder in golden retriever dogs that is maternally transmitted. Affected dogs are ataxic, have postural reaction deficits, and exhibit reduced spinal reflexes. They have no pronounced muscle atrophy nor do they seem to be in pain. In this study, we report the identification and characterization of the mutation causing SAN, a single base pair deletion in the mitochondrial tRNA^Tyr gene. The identification of this mutation makes it possible to eradicate the disease in golden retrievers. SAN constitutes a new animal model for mitochondrial disorders in humans. About 5 percent of the Swedish Golden Retriever population was found to carry the mutated gene, and screening has been developed to thwart further transmissions, researchers say.

Study Authors:

Izabella Baranowska¹, Karin Hultin Jäderlund^2,3, Inger Nennesmo⁴, Erik Holmqvist⁵, Nadja Heidrich⁵, Nils-Göran Larsson⁴, Göran Andersson¹, E. Gerhart H. Wagner⁵, Åke Hedhammar², Rolf Wibom⁴, Leif Andersson^1,6*

1 Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Uppsala, Sweden, 2 Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden, 3 Department of Companion Animal Clinical Sciences, Norwegian School of Veterinary Science, Oslo, Norway, 4 Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden, 5 Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden, 6 Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.

The full study can be viewed in the May 29 edition of the open-access journal PLoS Genetics.