Genomic Studies in the Dromedary (Camelus dromedarius)

Abstract

Camelids are an important livestock species in many regions of the world, often used for transportation and the production of wool/fiber, meat, and milk. Furthermore, they are used as exotic animals in zoos and shows, and they are used for riding or racing in many countries around the world. All camelid species are adapted to extreme environments. Dromedary and Bactrian camels are adapted to arid conditions, whereas alpacas and llamas are adapted to high altitude. This makes them unique organisms to study how their genetic make-up is related to their physiological features. Even though there has been an increased scientific interest in camelid genetics and genome analysis in the past decade, genetic studies on different traits and disorders are still limited. There are only a few reports about the genetics of camelid coat color and production traits and no genetic studies comparing these traits between dromedary populations. As selection has taken place since domestication, signatures of selection for different phenotypes can be traced using whole genome sequencing and bioinformatic tools. This will lead to the identification of genes that are associated with selected traits. We collected blood samples from 200 camels for DNA isolation and tissues for RNA isolation, cell suspensions and live cell cultures. DNA samples and cell suspensions were used for Sanger sequencing and fluorescent in situ hybridization to identify variants associated with coat color phenotypes and major coat color genes as well as locate these genes in camelid genomes. We preformed a whole genome sequencing of pooled dromedary samples investigate genetic differentiation in populations between different dromedary breeds. We identified genetic variants in the dromedary MC1R and ASIP genes that are associated with white and black coat colors, respectively. We identified a subset of genes under selection in dromedary populations and are associated with different traits, such as coat color, milk, and meat production. The overall objective of this project was to generate genetic and genomic resources for camelids (the dromedary in particular) and to identify genes that are associated with different coat color phenotypes and genes that are under selection in different dromedary populations.