Of all of the breeds of dog, the inheritance of sensorineural deafness has thus far been most extensively investigated in Dalmatians.
More than 90 dog breeds can suffer from congenital sensorineural deafness. Dog breeds carrying certain gene variants for piebald spotting or the so-called merle factor which disturbs the synthesis of colour pigments and causes a brightening of the coat colour are particularly affected.
Professor Ottmar Distl and Susanne Kluth from the Institute for Animal Breeding and Genetics of the University of Veterinary Medicine Hannover (TiHo) investigated the genetic causes for congenital sensorineural deafness in 235 Dalmatians. In order to do this, they screened more than 170.000 genetic variants distributed across the entire genome for sensorineural deafness. Their results provide the basis for a better understanding of the development of sensorineural deafness.
The researchers published them in the November issue of the online specialist magazine PLoS ONE (http://dx.plos.org/10.1371/journal.pone.0080642).
The genetic mechanisms which cause sensorineural deafness are very complex. Various gene variants are able to trigger the disease. “More than 90 percent of dogs with two or more gene variants for sensorineural deafness are affected by sensorineural deafness”, the researchers say. In their studies, the scientists found genes which affect the development of different structures in the inner ear. This includes the tectorial membrane, which is located within the cochlea, and the organ of Corti with its hair cells which convert acoustic signals into nerve signals and transmit them to the auditory nerve. Animals lacking the skin pigment cells known as melanocytes in their inner ears are also affected by sensorineural deafness.
Melanocytes have to migrate into the inner ear in order to complete important tasks for the formation of the acoustic hearing signal. Until now, this could only be verified in mouse models and a very rare natural mutation of white cattle.
The genetic knowledge now available provides the researchers of the University of Veterinary Medicine in Hannover with the basis to decipher the causes for congenital sensorineural deafness. Using the latest methods of genome analysis, they now start to compare the genome of dogs suffering from congenital sensorineural deafness with that of normally hearing dogs. The aim is to investigate congenital sensorineural deafness in as many dog and cat breeds as possible. “Only the knowledge of the genetic causes of the disease will help dog and cat breeders to prevent this inherited disease effectively and to organize their breeding programs appropriately, so our research is an important contribution to animal welfare”, says Distl. Scientists are currently developing a genome-wide test to detect sensorineural deafness. Dalmatian breeders can already ship EDTA blood samples (addition of EDTA prevents clotting of the blood) to the Institute for Animal Breeding and Genetics in Hannover, Germany (http://www.tiho-hannover.de/de/kliniken-institute/institute/institut-fuer-tierzu...). Breeders who want to support the development of tests for further dog and cat breeds can help by providing sample material (EDTA blood) and brainstem auditory evoked response (BAER) test results.
Of all of the breeds of dog, the inheritance of sensorineural deafness has thus far been most extensively investigated in Dalmatians. In the breeds Australian Cattle Dog, Boston Terrier, English Cocker Spaniel, English Setter, Jack Russell Terrier, Australian Shepherd and Border Collies, sensorineural deafness occurs more frequently when the animals are bred with stronger piebald spotting.Original publication
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