Known for their natural intelligence, balanced temperament and protective nature, German shepherds are one of the world’s most popular canine breeds. But there is a downside to this popularity. After more than a century of breeding for certain characteristics, German shepherds have been left vulnerable to many genetic diseases, particularly of the hip.
Yet help has arrived in the form of the first-ever complete map of the German shepherd genome. Not only will this sequence provide a biological snapshot of the dog species on the whole, but will also serve as a reference point for future research on the diseases that affect this breed.
“One of the most common health problems affecting German shepherds is canine hip dysplasia, which is a painful condition that can restrict their mobility,” Professor Bill Ballard, an evolutionary biologist at the University of New South Wales, Sydney, and corresponding author of the new research, explained in a statement. “Now that we have the genome, we can determine much earlier in life whether the dog is likely to develop the condition. And over time, it will enable us to develop a breeding program to reduce hip dysplasia in future generations.”
You may be wondering who is this dog, whose genome will now go down in the scientific history books? Described as an “easy-going and approachable 5.5-year-old,” the German shepherd Nala was selected to have her blood sampled and used in the study, published in GigaScience. As she was free of all known genetic diseases, as well as no sign of hip dysplasia, her genome can provide a healthy reference for future disease studies.
Nala’s genome will join the likes of other canines, such as Shadow the Poodle and Tasha the Boxer, whose DNA was sequenced around 15 years ago. In all cases, scientists had to grapple with the task of determining the exact order of 2.8 billion base pairs of DNA which make up 19,000 genes that are compacted into 38 pairs of chromosomes (plus the two sex chromosomes) of a dog. However, improvements in genetic sequencing technology over the last decade or so, means that the map of Nala’s genes is the most complete yet.
“The biggest difference between the mapping today and in 2005 is that we now use long read sequencing,” says Professor Ballard. “The Boxer’s genome was put together with ‘Sanger’ sequencing, which can read about 1,000 bases in length at a time, while the technology that is available today – Next Generation sequencing – can read up to 15,000 bases.”
What this means, Professor Ballard explained, is that if a length of DNA has a duplicated section of more than 1,000 bases the Sanger sequencing would not be able to tell you from which part it originated. Whilst in Sanger’s Boxer genome there were around 23,000 gaps, the Next Generation sequencing of Nala’s genome had just over 300.
“I would expect that as the costs come down, all the major breeds will have a genome mapped within 10 years,” Professor Ballard remarked, “because this will help identify specific diseases, and lots of breeds have known specific diseases.”
