Complex Genetics Underlie Deafness in the Dalmatian

01/19/2023
Author: Sharon M. Albright, DVM, CCRT

Congenital sensorineural deafness – a type of deafness present at birth – is reported in up to 30% of Dalmatians worldwide. The white coat pattern characteristic of Dalmatians is an established risk factor for deafness, but many studies of the MITF gene responsible for this coat pattern have failed to identify the genetic mutation(s) responsible for deafness. This means that the genetics of deafness in the Dalmatian are complex, previous studies have not had sufficient statistical power, or that other factors, such as how dogs are tested for deafness and how deafness is defined, are affecting the analysis. Additional studies are needed to understand the genes involved in this condition so that Dalmatian breeders can choose mating pairs that will decrease the incidence of deafness in their breed.

The genetics of congenital deafness in the Dalmatian are complex, but investigators have identified genetic markers associated with the condition as a first step toward genetic testing to help breeders plan mating pairs with a decreased risk of producing deaf offspring.

To help solve this puzzle, AKC Canine Health Foundation (CHF) funded investigators at the University of Sydney examined six chromosome regions previously identified as relevant to bilateral deafness (both ears affected) in the Dalmatian. (CHF Grant 02157-MOU: Genomics of Deafness in the Dalmatian) They combined results from a group of Dalmatians in Australia with data obtained from Dalmatians in the United States and the United Kingdom. They found three genetic markers on chromosome 20 and near the MITF gene that were associated with deafness.

Genetic markers and genes that are located close to each other on a chromosome are usually inherited together. Investigators were able to identify genetic markers associated with an increased risk for bilateral deafness in Dalmatians. Dogs with two copies of this high-risk genetic marker had a significantly higher risk of being deaf. However, not all dogs with two copies of the high-risk marker developed the deafness trait. This indicates that the trait has incomplete penetrance – that genetic mutations alone are not sufficient to cause deafness.

This analysis confirms that the genetics underlying congenital deafness in the Dalmatian are indeed complex. Investigators are continuing to collect data and refine their examination of the genetic regions of interest. The genetic markers identified represent a first step toward genetic testing to help breeders plan mating pairs with a decreased risk of producing deaf offspring. CHF and its donors will continue to fund important research like this to help breeders produce healthier dogs and to help all dogs live longer, healthier lives.

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