Fall is here, but the dog days of summer are still hanging around…well in the lab anyways. The power of DNA sequencing is being ‘unleashed’ and continues to bring light to the canine genome. By combining genome sequencing with bioinformatic pipelines that are able to identify SNPs (single nucleotide polymorphisms), researchers are able to elucidate differences in haplotype structure across several breeds and compare these variations against large-scale dog populations. These types of variations are similar to the variations found in human populations, and by understanding these patterns, researchers are able to better design gene mapping experiments for complex diseases.
The variation in dog breeds is extremely wide in physical, behavioral, and disease risk. Overall body size varies 40-fold in large and small breeds. More than 350 inherited diseases have been identified in domesticated dogs. Most of these diseases predominate in a single breed or a small group for breeds. Identifying gene variations that are associated with these diseases makes it possible to reduce their occurrence through selective breeding. For example, Transitional Cell Carcinoma (TCC) of the bladder is commonly found in Terriers and Shetland Sheep dogs.
Using next generation sequencing, a mutation in the BRAF gene has been identified and is present in 85% of TCC tumors. This mutation is identical to the BRAFV600E mutation that is very common in human tumors including melanomas, colon and thyroid cancers. Many highly specialized treatments are available for humans and preliminary trials have shown that canine tumors with this mutation respond to some of these drugs. Advancements in understanding this mutation has made it easy for dog owners to diagnose their pets, and sample collection is easy. The BRAF mutation in tumors is easily identified through DNA extraction from urine in 100% of dogs affected by TCC. By utilizing DNA extraction and sequencing of a urine sample as an early diagnosis method, an evasive biopsy is not necessary.