Canine Genetics and Genomics

In the past fifteen years, tremendous progress has been made in dog genomics. Several genetic aspects of cancer, heart disease, hip dysplasia, vision and hearing problems in dogs have been investigated and studied in detail. Genome-wide associative studies have made it possible to identify several genes associated with diseases, morphological and behavioral traits. The dog genome contains an extraordinary amount of genetic variability that distinguishes the different dog breeds. As a consequence of the selective programs, applied using stringent breed standards, each dog breed represents, today, a population isolated from the others. The availability of modern next generation sequencing (NGS) techniques and the identification of millions of single functional mutations (SNPs) has enabled us to obtain new and unknown detailed genomic data of the different breeds.

Dog10K_Boxer_Tasha_1.0: A Long-Read Assembly of the Dog Reference Genome

The domestic dog has evolved to be an important biomedical model for studies regarding the genetic basis of disease, morphology and behavior. Genetic studies in the dog have relied on a draft reference genome of a purebred female boxer dog named “Tasha” initially published in 2005. Derived from a Sanger whole genome shotgun sequencing approach coupled with limited clone-based sequencing, the initial assembly and subsequent updates have served as the predominant resource for canine genetics for 15 years. While the initial assembly produced a good-quality draft, as with all assemblies produced at the time, it contained gaps, assembly errors and missing sequences, particularly in GC-rich regions, which are found at many promoters and in the first exons of protein-coding genes. Here, we present Dog10K_Boxer_Tasha_1.0, an improved chromosome-level highly contiguous genome assembly of Tasha created with long-read technologies that increases sequence contiguity >100-fold, closes >23,000 gaps of the CanFam3.1 reference assembly and improves gene annotation by identifying >1200 new protein-coding transcripts. The assembly and annotation are available at NCBI under the accession GCF_000002285.5.

Expanding the genetic toolbox

Knowledge of canine genetics has advanced rapidly in recent years. Researchers say even deeper understanding is ahead, and that it could support a shift to more preventative veterinary care. But the involvement of a wide group of people will be vital in progressing towards that future.

Discovering disease causing variants in dogs through whole genome sequencing

This dissertation focuses on the use of whole genome sequencing (WGS) for the identification of disease causing variants in canine genomes. A brief review on the historical milestones of genetics, the creation and popularization of the fast throughput DNA sequencing technologies and their advantages and potential problems and biases, the importance of the study of canine genetics and the current state of the canine genome assembly is presented. Our lab sequenced [about]100 dogs in the attempt to discover disease-causing variants. So far 20 such variants have been identified. This dissertation contains detailed accounts of the discovery variants likely to be responsible for four canine diseases. Those diseases are: Paroxysmal dyskinesia in Soft Coated Wheaten Terriers that is associated to the missense mutation PIGN:c.398C greater than T; two different forms of neuronal ceroid lipofuscinosis, one in Australian Cattle dogs caused by CLN5:c.619C greater than T, and one in the Cane Corso caused by the splice site mutation PPT1c.124+1 [greater than] A; and a Shiba Inu GM2 gangliosidosis caused by HEXB.c:948_950delCCT. Furthermore, examples of not so successful attempts, possible reasons for failures and suggestions to successfully conclude other ongoing investigations.