Abstract
Canine coat color is a readily observed phenotype of great interest to dog enthusiasts; it is also an excellent avenue to explore the mechanisms of genetics and inheritance. As such, multiple commercial testing laboratories include basic color alleles in their popular screening panels, allowing for the creation of genotyped datasets at a scale not before appreciated in canine genetic research. These vast datasets have revealed rare genotype anomalies that encourage further exploration of color and pattern inheritance. We previously reported the simultaneous presence of greater than two allele variants at the Agouti Signaling Protein (ASIP) locus in a commercial genotype cohort of 11,790 canids. Here we present additional data to characterize the occurrence of anomalous ASIP genotypes. We document the detection of combinations of three or four ASIP allele variants in 17 dog breeds and Dingoes, at within-breed frequencies of 1.32–63.34%. We analyze the potential impact on phenotype that these allele combinations present, and propose mechanisms that could account for the findings, including: gene recombination, duplication, and incorrect causal variant identification. These findings speak to the accuracy of industry-wide protocols for commercial ASIP genotyping and imply that ASIP should be analyzed via haplotype, rather than using only the existing allele hierarchy, in the future.
Highlights
Canine coat color genetics is a subject of much interest to members of the dog breeding community, and the inherently visible and predominantly non-deleterious phenotypic presentation has encouraged many genetic research endeavors
Using data generated via commercial laboratory coat color genotype-testing, with direct testing of published variants, our goal was to describe the existence of A3+ alleles, report which breeds they are observed in and the frequencies of these results by breed, and present observed phenotypes for A3+ dogs
We have identified a situation that poses a challenge to commercial laboratories offering coat color genotyping, whereby a small portion of dogs will not correctly genotype for Agouti Signaling Protein (ASIP) if the aw allele is masked by a recombination situation
Summary
Canine coat color genetics is a subject of much interest to members of the dog breeding community, and the inherently visible and predominantly non-deleterious phenotypic presentation has encouraged many genetic research endeavors. Numerous commercial genotyping laboratories offer basic coat color assays. The conventional understanding and nomenclature of ASIP inheritance consists of four characterized alleles, present in a dominance hierarchy: ay > aw > at > a. The ay allele is the most dominant and is responsible for fawn coloring, which consists of pheomelanin (yellow- or red-based pigment) at the base of a hair with a eumelanin (black- or brown-based pigment) at the tip [2]. The aw allele, which is the wild-type allele of ASIP, produces a wolf-sable banded hair pattern. The aw allele is typically identified through a process of
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