Test Detail

Canine A locus (ASIP) Shiba inu

Dermatológico · Dog

The canine A locus (ASIP) regulates the distribution of eumelanin (black/brown) and pheomelanin (yellow/red) in the coat. It is not a simple recessive system: it is modulated by two independent promoters (the ventral promoter, VP, and the hair-cycle-specific promoter, HCP), whose combined activity generates the pattern. The sesame colour of the Shiba inu (red hairs with dark tips on the back) corresponds to specific allelic combinations of these promoters. It is a colour trait, not a disease.

Inheritance pattern	It is not a simple recessive trait: it depends on the combination of ASIP VP/HCP promoter haplotypes. Red sesame is associated with the heterozygous diplotype VP2-HCP1/VP2-HCP3 (haplotypes A^ys and a^t/BB1); darker sesame, with the a^w/a^t genotype.
Gene / Mutation	ASIP (A locus). There is no single mutation: the patterns are due to haplotypes defined by regulatory variants in two promoters, the ventral promoter (VP) and the hair-cycle-specific promoter (HCP). The proposed allelic series (Bannasch et al. 2021) is DY > SY > AG > BS > BB > a. The Shiba inu sesame is associated with the diplotype VP2-HCP1/VP2-HCP3 (Belyakin et al. 2022): VP2-HCP1 corresponds to haplotype A^ys and VP2-HCP3 to haplotype a^t/BB1. OMIA000201-9615.
Penetrance	Pattern expression is consistent with the diplotype, but its intensity (amount of dark overtones) is variable and modulated by other colour loci and by the breed's genetic background. It is not a pathological trait with clinical penetrance.
Code	korq
Turnaround time	7 days
Price	41,60 €

Incidence

The sesame pattern is characteristic of the Shiba inu. In the study by Belyakin et al. (2022) the red sesame dogs carried the diplotype VP2-HCP1/VP2-HCP3. Population frequencies by breed: limited data.

Breeder management

- Sesame is a colour trait, not a defect or a disease.\n- Knowing the promoter haplotypes (VP/HCP) of the breeding animals makes it possible to plan the litter's pattern.\n- Tests based only on associated markers may give discordant results; interpret with caution.\n- Do not over-select for a pattern if this reduces the breed's genetic variability.

Specialist notes

The canine A locus is a modular system of promoters (VP and HCP) and not a classic series of coding mutations; some commercial tests use markers in linkage disequilibrium, with the possibility of discordant results (Bannasch et al. 2021). The Shiba inu sesame is an aesthetic trait with no pathological implication.

References

1. Bannasch DL et al. 2021. Dog colour patterns explained by modular promoters of ancient canid origin. Nature Ecology & Evolution. PMID: 34385618
2. Belyakin SN et al. 2022. ASIP Promoter Variants Predict the Sesame Coat Color in Shiba Inu Dogs. Veterinary Sciences. PMID: 35622750
3. OMIA:000201-9615. Coat colour, agouti in Canis lupus familiaris. Online Mendelian Inheritance in Animals.

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